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If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: Mariner Mission to Venus - -Author: Jet Propulsion Laboratory - -Release Date: April 21, 2017 [EBook #54585] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK MARINER MISSION TO VENUS *** - - - - -Produced by Stephen Hutcheson and the Online Distributed -Proofreading Team at http://www.pgdp.net - - - - - - - [Illustration: Mariner spacecraft] - - - - - MARINER - _MISSION TO VENUS_ - - -Prepared for the National Aeronautics and Space Administration BY THE -STAFF, Jet Propulsion Laboratory, California Institute of Technology -COMPILED BY HAROLD J. WHEELOCK FOREWORD BY W. H. PICKERING, Director, -Jet Propulsion Laboratory, California Institute of Technology - - McGRAW-HILL BOOK COMPANY, INC. - New York, San Francisco, Toronto, London - - -MARINER MISSION TO VENUS - -Copyright © 1963 by the Jet Propulsion Laboratory, California Institute -of Technology. All Rights Reserved. Printed in the United States of -America. - -Library of Congress Catalog Card Number 63-17489. - -This book describes one phase of the U. S. civilian space program—the -journey of the Mariner spacecraft to the vicinity of Venus and beyond. -It reports upon the measurements taken during the “flyby” on December -14, 1962, when Mariner reached a point 21,598 miles from the planet, and -36,000,000 miles from Earth (communication with the spacecraft was -continued up to a distance of approximately 54,000,000 miles from -Earth). The Mariner mission was a project of the National Aeronautics -and Space Administration, carried out under Contract No. NAS 7-100 by -the Jet Propulsion Laboratory, California Institute of Technology. - - -FOREWORD - -For many centuries scientific information about the planets and the vast -void that separates them has been collected by astronomers observing -from the surface of the Earth. Now, with the flight of Mariner II, we -suddenly have in our hands some 90 million bits of experimental data -measured in the region between Earth and the planet Venus. Thus, man for -the first time has succeeded in sending his instruments far into the -depths of space, and indeed, in placing them near another planet. A -whole new area of experimental astronomy has been opened up. - -This book is a brief record of the Mariner Project to date and is -designed to explain in general terms the preliminary conclusions. -Actually, it will be months or years before all of the data from Mariner -II have been completely analyzed. The most important data were the -measurements made in the vicinity of the planet Venus, but it should -also be noted that many weeks of interplanetary environmental -measurements have given us new insight into some of the basic physical -phenomena of the solar system. The trajectory data have provided new, -more accurate measurements of the solar system. The engineering -measurements of the performance of the spacecraft will be of inestimable -value in the design of future spacecraft. Thus, the Mariner II -spacecraft to Venus not only looks at Venus but gives space scientists -and engineers information helpful in a wide variety of space ventures. - -A project such as Mariner II is first a vast engineering task. Many -thousands of man-hours are required to design the complex automatic -equipment which must operate perfectly in the harsh environment of -space. Every detail of the system must be studied and analyzed. The -operations required to carry out the mission must be understood and -performed with precision. A successful mission requires every member of -the entire project team to do his task perfectly. Whether it be the -error of a designer, mechanic, mathematician, technician, operator, or -test engineer—a single mistake, or a faulty piece of workmanship, may -cause the failure of the mission. Space projects abound with examples of -the old saying, “For want of a nail, the shoe was lost ...,” and so on, -until the kingdom is lost. Only when every member of the project team is -conscious of his responsibility will space projects consistently -succeed. - -The Mariner II Project started with the Lunar and Planetary Projects -Office of the Office of Space Sciences at NASA in Washington. Jet -Propulsion Laboratory, California Institute of Technology, personnel -provided the main body of the team effort. They were heavily supported -by industrial contractors building many of the subassemblies of the -spacecraft, by scientists planning and designing the scientific -experiments, and by the Air Force which supplied the launching rockets. -Several thousand men and women had some direct part in the Mariner -Project. It would be impossible to list all of those who made some -special contribution, but each and every member of the project performed -his job accurately, on time, and to the highest standards. - -Mariner II is only a prelude to NASA’s program of unmanned missions to -the planets. Missions to Mars as well as Venus will be carried out. -Spacecraft will not only fly by the planets as did Mariner II, but -capsules will be landed, and spacecraft will be put into orbit about the -planets. The next mission in the Mariner series will be a flyby of the -planet Mars in 1965. - -By the end of the decade, where will we be exploring, what will new -Mariners have found? Will there be life on Mars, or on any other planet -of the solar system? What causes the red spot on Jupiter? What is at the -heart of a comet? These and many other questions await answers obtained -by our future spacecraft. Mariner II is just a beginning. - - W. H. Pickering - _Director_ - Jet Propulsion Laboratory_ - California Institute of Technology_ - April, 1963_ - - -CONTENTS - - - _FOREWORD_ - _ACKNOWLEDGMENTS_ - - - CHAPTER 1 VENUS - _The Double Star of the Ancient World_ - _The Consensus prior to Mariner II_ - _The Cytherean Riddle: Living World or Incinerated Planet_ - - - CHAPTER 2 PREPARING FOR SPACE - _A Problem in Celestial Dynamics_ - _The Organization_ - _NASA: For Science_ - _JPL: JATO to Mariner_ - _General Dynamics: The Atlas_ - _Lockheed: Agena B_ - - - CHAPTER 3 THE SPACECRAFT - _The Spaceframe_ - _The Power System_ - _CC&S: The Brain and the Stopwatch_ - _Telecommunications: Relaying the Data_ - _Attitude Control: Balancing in Space_ - _Propulsion System_ - _Temperature Control_ - _The Scientific Instruments_ - - - CHAPTER 4 THE LAUNCH VEHICLE - _The Atlas Booster: Power of Six 707’s_ - _The Agena B: Start and Restart_ - - - CHAPTER 5 FLIGHT INTO SPACE - _Mariner I: An Abortive Launch_ - _Mariner II: A Roll before Parking_ - _The Parking Orbit_ - _Orientation and Midcourse Maneuver_ - _The Long Cruise_ - _Encounter and Beyond_ - _The Record of Mariner_ - - - CHAPTER 6 THE TRACKING NETWORK - _Deep Space Instrumentation Facility_ - _The Goldstone Complex_ - _The Woomera Station_ - _The Johannesburg Station_ - _Mobile Tracking Station_ - - - CHAPTER 7 THIRTEEN MILLION WORDS - _Communication Control_ - _The Operations Center_ - _Central Computing Facility_ - - - CHAPTER 8 THE SCIENTIFIC EXPERIMENTS - _Data Conditioning System_ - _Cosmic Dust Detector_ - _Solar Plasma Experiment_ - _High-energy Radiation Experiment_ - _The Magnetometer_ - _Microwave Radiometer_ - _Infrared Radiometer_ - _Mariner’s Scientific Objectives_ - - - CHAPTER 9 THE LEGACY OF MARINER - _Space without Dust?_ - _The Ubiquitous Solar Wind_ - _High-energy Particles: Fatal Dosage?_ - _A Magnetic Field?_ - _The Surface: How Hot?_ - _Cloud Temperatures: The Infrared Readings_ - _The Radar Profile: Measurements from Earth_ - - - CHAPTER 10 THE NEW LOOK OF VENUS - _APPENDIX_ - _INDEX_ - - -ACKNOWLEDGMENTS - -Researching the material, gathering and comparing data, preparation of -review drafts and attending to the hundreds of details required to -produce a document on the results of such a program as the Mariner -mission to Venus is a tremendous task. Special acknowledgment is made to -Mr. Harold J. Wheelock who, on an extremely short time scale, carried -the major portion of this work to completion. - -Although the prime sources for the information were the Planetary -Program office and the Technical Divisions of the Jet Propulsion -Laboratory, other organizations were extremely helpful in providing -necessary data, notably the George C. Marshall Space Flight Center, the -Lockheed Missiles and Space Company, the Astronautics Division of the -General Dynamics Corporation, and, of course, the many elements of the -National Aeronautics and Space Administration. - -JPL technical information staff members who assisted Mr. Wheelock in -production of the manuscript and its illustrations were Mr. James H. -Wilson, Mr. Arthur D. Beeman and Mr. Albert E. Tyler. JPL is also -grateful to Mr. Chester H. Johnson for his help and suggestions in -preparing the final manuscript. - - - - - CHAPTER 1 - VENUS - - -Halfway between Los Angeles and Las Vegas, the California country climbs -southward out of the sunken basin of Death Valley onto the -3500-foot-high floor of the Mojave desert. - -On this immense plateau in an area near Goldstone Dry Lake, about 45 -miles north of the town of Barstow, a group of 85-foot antennas forms -the nucleus of the United States’ world-wide, deep-space tracking -network. - -Here, on the morning of December 14, 1962, several men were gathered in -the control building beneath one of the antennas, listening intently to -the static coming from a loudspeaker. They were surrounded by the exotic -equipment of the space age. Through the window loomed the gleaming metal -framework of an antenna. - -Suddenly a voice boomed from the loudspeaker: “The numbers are changing. -We’re getting data!” - -The men broke into a cheer, followed by an expectant silence. - -Again the voice came from the speaker: “The spacecraft’s crossing the -terminator ... it’s still scanning.” - -At that moment, some 36 million miles from the Earth, the National -Aeronautics and Space Administration’s Mariner[1] spacecraft was passing -within 21,600 miles of the planet Venus and was radioing back -information to the Goldstone Station—the first scientific data ever -received by man from the near-vicinity of another planet. - -At the same time, in Washington, D.C., a press conference was in -progress. Mr. James E. Webb, Administrator of the National Aeronautics -and Space Administration, and Dr. William H. Pickering, Director of the -Jet Propulsion Laboratory, stood before a bank of microphones. In a few -moments, Dr. Pickering said, the audience would hear the sound of -Mariner II as it transmitted its findings back to the Earth. - -Then, a musical warble, the voice of Mariner II, resounded in the hall -and in millions of radios and television sets around the nation. -Alluding to the Greek belief that harmonious sounds accompanied the -movement of the planets, Dr. Pickering remarked that this, in truth, was -the music of the spheres. - -Mariner II had been launched from Cape Canaveral, Florida, on August 27, -1962. Its arrival at Venus was the culmination of a 109-day journey -through the strange environment of interplanetary space. The project had -gone from the drawing board to the launching pad in less than 11 months. -Mariner had taxed the resources and the manpower of the Jet Propulsion -Laboratory, California Institute of Technology; the Atlantic Missile -Range centering at Cape Canaveral; theoretical and experimental -laboratories at several universities and NASA centers; numerous elements -of the aerospace industry; and, of course, NASA management itself. - -To the considerable body of engineers scattered around the world from -Pasadena to Goldstone to South Africa to Australia, the warble of -Mariner was something more than “the music of the spheres.” Intercept -with Venus was the climax of 109 days of hope and anxiety. - -To the world at large, this warbling tone was a signal that the United -States had moved ahead—reached out to the planets. Mariner was exploring -the future, seeking answers to some of the unsolved questions about the -solar system. - - -THE DOUBLE STAR OF THE ANCIENT WORLD - -Venus, the glittering beacon of our solar system, has intrigued man for -at least 4,000 years. The Babylonians first mentioned the brilliant -planet on clay tablets as early as 2,000 years before Christ. The -Egyptians, the Greeks, and the Chinese had thought of Venus as two stars -because it was visible first in the morning and then in the evening sky. -The Greeks had called the morning star Phosphorus and the evening star -Hesperos. By 500 B.C. Pythagoras, the Greek philosopher, had realized -that the two were identical. - -Galileo discovered the phases of Venus in 1610. Because of the planet’s -high reflectivity, Copernicus falsely concluded that Venus was either -self-luminous or else transparent to the rays of the Sun. - -Venus was tracked across the face of the Sun in 1761, from which event -the presence of an atmosphere about the planet was deduced because of -the fuzzy edges of the image visible in the telescope. Throughout the -eighteenth and nineteenth centuries, Venus continued to excite growing -scientific curiosity in Europe and America. - - [Illustration: _Venus’ orbit is almost circular. At inferior - conjunction, the planet is between the Earth and the Sun, - approximately 26,000,000 miles away; at superior conjunction, Venus - is on the other side of the Sun. The elongations are the farthest - points to the east and the west of the Earth._] - -Even the development of giant telescopes and the refinement of -spectroscopic and radar astronomy techniques in recent times had yielded -few indisputable facts about Venus. Until radar studies, made from -Goldstone, California, in 1962, neither the rate nor the angle of axial -spin could be determined with any degree of accuracy. The ever-shifting -atmosphere continued to shield the Venusian surface from visual -observation on Earth, and the nature of its atmosphere became an -especially controversial mystery. - - -THE CONSENSUS PRIOR TO MARINER II - -Venus is a virtual twin of the Earth; it approaches our planet closer -than any celestial body except the Moon, a few vagrant comets, and other -such galactic wanderers. Long fabled in song and legend as the most -beautiful object in the sky, Venus has an albedo, or reflectivity -factor, of 59% (the Moon has one of 7%). In its brightest or crescent -phase, Venus glows like a torch, even casting a distinct shadow—the only -body other than the Sun and the Moon yielding such light. - -Venus’ diameter is approximately 7,700 miles, compared with Earth’s -7,900. Also as compared with 1.0 for the Earth, Venus’ mean density is -0.91, the mass 0.81, and the volume 0.92. - -The Cytherean orbit (the adjective comes from Cytherea, one of the -ancient Greek names for Aphrodite—or in Roman times, Venus—the goddess -of love) is almost a perfect circle, with an eccentricity (or -out-of-roundness) of only 0.0068, lowest of all the planets. Venus rides -this orbital path at a mean distance from the Sun of 67.2 million miles -(Earth is 93 million miles), and at a mean orbital speed of 78,300 miles -per hour, as compared with Earth’s 66,600 miles per hour. - -It also has a shorter sidereal period (revolution around the Sun or -year): 224 Earth days, 16 hours, 48 minutes. Estimates of the Venus -rotational period, or the length of the Venus day, have ranged from -approximately 23 Earth hours to just over 224 Earth days. The latter -rotation rate would be almost equivalent to the Venusian year and, in -such case, the planet would always have the same face to the Sun. - -Venus approaches within 26 million miles of the Earth at inferior -conjunction, and is as far away as 160 million miles at superior -conjunction, when it is on the opposite side of the Sun. - -The escape velocity (that velocity required to free an object from the -gravitational pull of a planet) on Venus is 6.3 miles per second, -compared with Earth’s escape velocity of 7 miles per second. The gravity -of the Earth is sufficient to trap an oxygen-bearing atmosphere near the -terrestrial surface. Because the escape velocity of Venus is about the -same as that of Earth, men have long believed (or hoped) that the -Cytherean world might hold a similar atmosphere and thus be favorable to -the existence of living organisms as we know them on the Earth. From -this speculation, numerous theories have evolved. - - -THE CYTHEREAN RIDDLE: LIVING WORLD OR INCINERATED PLANET - -Before Mariner II, Venus probably caused more controversy than any other -planet in our solar system except Mars. Observers have visualized Venus -as anything from a steaming abode of Mesozoic-like creatures such as -were found on the Earth millions of years ago, to a dead, noxious, and -sunless world constantly ravaged by winds of incredible force. - -Conjectures about the Venusian atmosphere have been inescapably tied to -theories about the Venusian topography. Because the clouds forming the -Venusian atmosphere, as viewed from the Earth through the strongest -telescopes, are almost featureless, this relationship between atmosphere -and topography has posed many problems. - -Impermanent light spots and certain dusky areas were believed by some -observers to be associated with Venusian oceans. One scientist believed -he identified a mountain peak which he calculated as rising more than 27 -miles above the general level of the planet. - -Another feature of the Venusian topography is the lack of (detectable) -polar flattening. The Earth does have such a flattening at the poles and -it was reasoned that, because Venus did not, its rate of rotation must -be much slower than that of the Earth, perhaps as little as only once -during a Venusian year, thus keeping one face perpetually toward the -Sun. - -Another school of thought speculated that Venus was covered entirely by -vast oceans; other observers concluded that these great bodies of water -have long since evaporated and that the winds, through the Cytherean -ages, have scooped up the remaining chloride salts and blasted them into -the Venusian skies, thus forming the clouds. - -Related to the topographic speculations were equally tenuous theories -about its atmosphere. It was reasoned that if the oceans of Venus still -exist, then the Venusian clouds may be composed of water droplets; if -Venus were covered by water, it was suggested that it might be inhabited -by Venusian equivalents of Earth’s Cambrian period of 500 million years -ago, and the same steamy atmosphere could be a possibility. - -Other theories respecting the nature of the Venusian atmosphere, -depending on how their authors viewed the Venusian terrain, included -clouds of hydrocarbons (perhaps droplets of oil), or vapors of -formaldehyde and water. Finally, the seemingly high temperature of the -planet’s surface, as measured by Earth-bound instruments, was credited -by some to the false indications that could be given by a Cytherean -ionosphere heavily charged with free electrons. - - [Illustration: _As seen from Earth, Venus is brightest at its - crescent phases as shown in these six photographs made by the - 100-inch telescope at Mt. Wilson, California._] - -However, the consensus of pre-Mariner scientific thinking seemed -generally to indicate no detectable free oxygen in the atmosphere; this -fact inveighed against the probability of surface vegetation, because -Earth-bound vegetation, at least, uses carbon dioxide and gives off -oxygen into the atmosphere. On the other hand, a preponderance of carbon -dioxide in the Venusian atmosphere was measured which would create a -greenhouse effect. The heat of the Sun would be trapped near the surface -of the planet, raising the temperature to as high as 615 degrees F. If -the topography were in truth relatively flat and the rate of rotation -slow, the heating effect might produce winds of 400 miles per hour or -more, and sand and dust storms beyond Earthly experience. And so the -controversy continued. - -But at 1:53.13.9 a.m., EST, on August 27, 1962, the theories of the past -few centuries were being challenged. At that moment, the night along the -east Florida coast was shattered by the roar of rocket engines and the -flash of incandescent exhaust streams. The United States was launching -Mariner II, the first spacecraft that would successfully penetrate -interplanetary space and probe some of the age-old mysteries of our -neighbor planet. - - - - - CHAPTER 2 - PREPARING FOR SPACE - - -In the summer of 1961, the United States was pushing hard to strengthen -its position in the exploration of space and the near planets. The -National Aeronautics and Space Administration was planning two projects, -both to be launched by an Atlas booster and a Centaur high-energy second -stage capable of much better performance than that available from -earlier vehicles. - -The Mariner program had two goals: Mariner A was ticketed for Venus and -Mariner B was scheduled to go to Mars. Caltech’s Jet Propulsion -Laboratory had management responsibility under NASA for both projects. -These spacecraft were both to be in the 1,000- to 1,250-pound class. -Launch opportunities for the two planets were to be best during the -1962-1964 period and the new second-stage booster known as Centaur was -expected to be ready for these operations. - -But trouble was developing for NASA’s planners. By August, 1961, it had -become apparent that the Centaur would not be flying in time to take -advantage of the 1962 third-quarter firing period, when Venus would -approach inferior conjunction with the Earth. JPL studied the problem -and advised NASA that a proposed lightweight, hybrid spacecraft -combining certain design features of Ranger III (a lunar spacecraft) and -Mariner A could be launched to Venus in 1962 aboard a lower-powered -Atlas-Agena B launch vehicle. - - [Illustration: _The Mariner II spacecraft was launched by an Atlas - first-stage booster vehicle and an Agena B second stage with restart - capability._] - - ATLAS-AGENA ADAPTER - AGENA B - MARINER SPACECRAFT - SHROUD - -The proposed spacecraft would be called Mariner R and was to weigh about -460 pounds and carry 25 pounds of scientific instruments (later -increased to 40 pounds). The restart capability of Agena was to be used -in a 98-statute-mile parking orbit. (The orbit was later raised to 115 -statute miles and the spacecraft weight was reduced to about 447 -pounds.) - -Two spacecraft would be launched one after the other from the same pad -within a maximum launch period extending over 56 days from July to -September, 1962. The minimum launch separation between the two -spacecraft would be 21 days. - -As a result of the JPL recommendations, NASA cancelled Mariner A in -September, 1961, and assigned JPL to manage a Mariner R Project to fly -two spacecraft (Mariner I and II) to the vicinity of Venus in 1962. -Scientific measurements were to be made in interplanetary space and in -the immediate environs of the planet, which would also be surveyed in an -attempt to determine the characteristics of its atmosphere and surface. -Scientific and engineering data would also be transmitted from the -spacecraft to the Earth while it was in transit and during the encounter -with Venus. - -Scientists and engineers were now faced with an arduous task. Within an -11-month period, on a schedule that could tolerate no delays, two -spacecraft had to be designed, developed, assembled, tested, and -launched. In order to meet the schedule, tested flight assemblies and -instruments would have to be in the Pasadena assembly facility by -mid-January, 1962, just four months after the start of the project. -Probably no other major space project of similar scope had ever been -planned on such a demanding schedule. - - [Illustration: _Mariner II travelled across 180 million miles of - space within our solar system as it spanned the gap between Earth - and Venus (shown here as the third and second planets, respectively, - from the Sun)._] - -With the shipment of equipment to Atlantic Missile Range (AMR) scheduled -for 9½ months after inception of the project, management and design -teams went all-out on a true “crash” effort. Quick decisions had to be -made, a workable design had to be agreed upon very early, and, once -established, the major schedule objectives could not be changed. Certain -design modifications and manufacturing changes in the Atlas-Agena launch -vehicle were also necessary. - -Wherever possible, Ranger design technology had to be used in the new -spacecraft and adapted to the requirements of a planetary probe. Other -necessary tasks included trajectory calculation; arrangements for -launch, space flight, and tracking operations; and coordination of AMR -Range support. - -Following NASA’s September, 1961 decision to go ahead with the Mariner R -Project, JPL’s Director, Dr. William H. Pickering, called on his -seasoned team of scientists and engineers. Under Robert J. Parks, -Planetary Program Director, Jack N. James was appointed as Project -Manager for Mariner R, assisted by W. A. Collier. Dan Schneiderman was -appointed Spacecraft System Manager, and Dr. Eberhardt Rechtin headed -the space tracking program, with supervision of the Deep Space -Instrumentation Facility (DSIF) operations under Dr. Nicholas Renzetti. -The Mariner space flight operations were directed by Marshall S. -Johnson. - - -A PROBLEM IN CELESTIAL DYNAMICS - -In order to send Mariner close enough to Venus for its instruments to -gather significant data, scientists had to solve aiming and guidance -problems of unprecedented magnitude and complexity. - -The 447-pound spacecraft had to be catapulted from a launching platform -moving around the Sun at 66,600 miles per hour, and aimed so precisely -that it would intercept a planet moving 78,300 miles per hour (or 11,700 -miles per hour faster than the Earth) at a point in space and time some -180.2 million miles away and 109 days later, with only one chance to -correct the trajectory by a planned midcourse maneuver. - -And the interception had to be so accurate that the spacecraft would -pass Venus within 8,000 to 40,000 miles. The chances of impacting the -planet could not exceed 1 in 1,000 because Mariner was not sterilized -and might contaminate Venus. Also, much more data could be gathered on a -near-miss flight path than on impact. Furthermore, at encounter (in the -target area) the spacecraft had to be so positioned that it could -communicate with Earth, see the Sun with its solar panels, and scan -Venus at the proper angles. - -Along the way, Mariner had to be able to orient itself so that its solar -panels were facing or “locked onto” the Sun in order to generate its own -power; acquire and maintain antenna orientation to the Earth; correct -its attitude constantly to hold Earth and Sun lock; receive, store, and -execute commands to alter its course for a closer approach to Venus; and -communicate its findings to Earth with only 3 watts of radiated power -and over distances never before spanned. - - [Illustration: _Mariner II was launched in a direction opposite to - the orbital travel of the Earth. The Sun’s gravity then pulled it in - toward the planet Venus._] - -Early in the program it had been decided that two spacecraft would be -launched toward Venus. Only 56 days were available for both launchings -and the planet would not be close enough again for 19 months—the period -between inferior conjunctions or the planet’s closest approach to the -Earth. On any one of these days, a maximum of 2 hours could be used for -getting the vehicles off the launch pad. In addition, the Mariners would -have to leave the Earth in a direction opposite to that of the Earth’s -direction of orbital revolution around the Sun. This flight path was -necessary so the spacecraft could then fall in toward the Sun and -intercept Venus, catching and passing the Earth along the way, about 65 -days and 11.5 million miles out. - -This feat of celestial navigation had to be performed while passing -through the hostile environment of interplanetary space, where the probe -might be subjected to solar winds (charged particles) travelling at -velocities up to 500 miles per second; intense bombardment from cosmic -radiation, charged protons, and alpha particles moving perhaps 1.5 -million miles per hour; radiated heat that might raise the spacecraft -temperatures to unknown values; and the unknown dangers from cosmic -dust, meteorites, and other miscellaneous space debris. - -In flight, each spacecraft would have to perform more than 90,000 -measurements per day, reporting back to the Earth on 52 engineering -readings, the changes in interplanetary magnetic fields, the density and -distribution of charged particles and cosmic dust, and the intensity and -velocity of low-energy protons streaming out from the Sun. - -At its closest approach to Venus, the spacecraft instruments would be -required to scan the planet during a brief 35-minute encounter, to -gather data that would enable Earth scientists to determine the -temperature and structure of the atmosphere and the surface, and to -process and transmit that data back to the Earth. - - -THE ORGANIZATION - -Flying Mariner to Venus was a team effort made possible through the -combined resources of several United States governmental organizations -and their contractors, science, and industry. The success of the Mariner -Project resulted primarily from the over-all direction and management of -the National Aeronautics and Space Administration and the Jet Propulsion -Laboratory, and the production and launch capabilities of the vehicle -builders and the Air Force. Several organizations bore the major -responsibility: NASA Headquarters, JPL, NASA’s Marshall Space Flight -Center and Launch Operations Center, Astronautics Division of General -Dynamics, and Lockheed Missiles and Space Company. - - -NASA: FOR SCIENCE - -The National Aeronautics and Space Administration was an outgrowth of -the participation of the United States in the International Geophysical -Year program and of the nation’s space effort, revitalized following -Russia’s successful orbiting of Sputnik I in 1957. - - [Illustration: _Final NACA meeting, August 21, 1958._] - - [Illustration: _Model of X-1 research plane._] - - [Illustration: _Headquarters of National Aeronautics and Space - Administration, Washington, D.C._] - - [Illustration: _JPL developed first JATO units in 1941._] - - [Illustration: _Other Laboratory Projects were the Corporal missile - (left) and Explorer I (right), the first U.S. satellite._] - -Under the terms of the law which created NASA, it is a Federal Agency -dedicated to carrying out “activities in space ... devoted to peaceful -purposes for the benefit of all mankind.” NASA is charged to preserve -the role of our nation as a leader in the aeronautical and space -sciences and technology and to utilize effectively the science and -engineering resources of the United States in accomplishing these goals. -Activities associated with military operations in space and the -development of weapons systems are specifically assigned to the Defense -Department. - -In November, 1957, before the creation of NASA, President Eisenhower had -established a Scientific Advisory Committee to determine the national -objectives and requirements in space and to establish the basic -framework within which science, industry, and the academic community -could best support these objectives. - -The Committee submitted a report to the President in March, 1958, -recommending creation of a civilian agency to conduct the national space -programs. The recommendation, endorsed by the President, was submitted -to the Congress on April 2, 1958. The National Aeronautics and Space Act -of 1958 was passed and became law in July, 1958. - -NASA was officially established on October 1, 1958, and Dr. T. Keith -Glennan, President of Case Institute of Technology, was appointed as the -first Administrator. The facilities and personnel of the National -Advisory Committee for Aeronautics (NACA) were transferred to form the -nucleus of the new NASA agency. - -NACA had performed important and significant research in aeronautics, -wind tunnel technology, and aerodynamics since 1915, including a series -of experimental rocket research aircraft that culminated in the X-15. It -was natural that it be expanded to include space operations. - -Among the NACA Centers transferred to NASA were the Langley Research -Center at Hampton, Virginia; Lewis Research Center, Cleveland, Ohio; -Ames Research Center, Moffett Field, California; Flight Research Center, -Edwards, California; and the rocket launch facility at Wallops Island, -Virginia. - -Those personnel of the Naval Research Laboratory who had been working on -Project Vanguard were also transferred to NASA, as was the project. -These personnel are now part of the new Goddard Space Flight Center at -Greenbelt, Maryland. - -The October, 1958, transfers also included a number of the space -projects of the Advanced Research Projects Agency of the Defense -Department. In a December, 1958, Executive Order, the President assigned -the former Army facilities of the Jet Propulsion Laboratory at Pasadena, -California, to NASA. At the same time, the group working under Dr. -Wernher von Braun at the Army Ballistic Missile Agency (commanded by -Major General John B. Medaris) was made responsive to NASA requirements. - -On July 1, 1960, the George C. Marshall Space Flight Center (MSFC) was -organized at Huntsville under von Braun’s direction. The former -Development Operations Division of ABMA formed the nucleus of the new -Center. The MSFC mission was to procure and to supervise the adaptation -of launch vehicles for NASA space missions, including Atlas, Thor, and -Agena. Marshall is directly responsible for the design and development -of advanced, high-thrust booster vehicles such as the Saturn C-1 and C-5 -and the Nova. - -An agency to conduct NASA affairs at Cape Canaveral was formed within -MSFC on July 1, 1960. Known then as the Launch Operations Directorate -(LOD), it was directed by Dr. Kurt H. Debus. LOD became independent of -Marshall in March, 1962, when it was redesignated the Launch Operations -Center (LOC), reporting directly to the Office of Manned Space Flight. -This separation resulted largely because the activities at AMR were -becoming more operational in character and less oriented toward research -and development. - -LOC handles such functions for NASA as the scheduling of launch dates -and liaison with the Atlantic Missile Range for support activities. The -Center will have the responsibility in the field for assembly, checkout, -and launch of the Saturn and Nova boosters. - -Following the election of President Kennedy in 1961, James E. Webb -replaced Dr. Glennan as Administrator of NASA. Shortly after, a new -national goal was announced—placing a man on the Moon and returning him -safely to the Earth in this decade. Meanwhile, JPL had been assigned -responsibility for unmanned exploration of the Moon, the planets, and -interplanetary space, and thus was charged with supporting the NASA -manned flight program through these activities. - -In less than five years, NASA grew to include eight flight and research -centers and about 21,000 technical and management personnel. Within -NASA, Dr. Abe Silverstein’s Office of Space Flight Programs was -responsible for the Mariner R Project which was directly assigned to Ed -Cortright, Director of Lunar & Planetary Programs, and Fred -Kochendorfer, who is NASA’s Program Chief for Mariner. A subsequent -reorganization placed responsibility under Dr. Homer Newell’s Office of -Space Sciences, and Oran Nicks became Director of Lunar & Planetary -Programs. - - -JPL: JATO TO MARINER - -The Jet Propulsion Laboratory, staffed and operated for NASA by -California Institute of Technology, had long been active in research and -development in the fields of missiles, rockets, and the space-associated -sciences. The first government-sponsored rocket research group in the -United States, JPL had originated on the Caltech campus in 1939, an -outgrowth of the Guggenheim Aeronautical Laboratories, then headed by -celebrated aerodynamicist Dr. Theodore von Karman. - -Von Karman and his associates moved their operation to a remote spot at -the foot of the San Gabriel mountains and, working from this base, in -1941 the pioneering group developed the first successful jet-assisted -aircraft takeoff (JATO) units for the Army Air Force. The Laboratory -began a long association with the Army Ordnance Corps in 1944, when the -Private A test rocket was developed. In retrospect, it is now recognized -that the Private A was the first U. S. surface-to-surface, -solid-propellant rocket. Its range was 10 miles! - -JPL’s WAC Corporal rocket set a U. S. high-altitude record of 43.5 miles -in 1945. Mounted on a German V-2 as the Bumper-WAC, it achieved an -altitude record of 250 miles in 1947. More important, this event was the -first successful in-flight separation of a two-stage rocket—the -feasibility of space exploration had been proved. - -After the end of World War II, JPL research set the stage for -high-energy solid-propellant rockets. For the first time the solid -propellants, which contained both fuel and oxidizers, were cast in -thin-walled cases. Techniques were then developed for bonding the -propellants to the case, and burning radially outward from the central -axis was achieved. Attention was then turned to increasing the energy of -the propellants. - -By 1947, the Corporal E, a new liquid-propellant research rocket, was -being fired. JPL was asked to convert it into a tactical weapon in 1949. -The Corporal E then became the first liquid-propellant -surface-to-surface guided missile developed by the United States or the -Western bloc of nations. - -Because of the need for higher mobility and increased firing rate, JPL -later designed and developed the solid-propellant Sergeant—the nation’s -first “second-generation” weapon system. This inertially guided missile -was immune to electronic countermeasures by an enemy. - -Meanwhile, JPL scientists had pioneered in the development of electronic -telemetering techniques, which permit an accurate monitoring of system -performance while missiles are in flight. By 1944, Dr. William H. -Pickering, a New Zealand born and Caltech-trained physicist who had -worked with Dr. Robert Millikan in cosmic ray research, had been placed -in charge of the telemetering effort at JPL. Pickering became Director -of the Laboratory in 1954. - -Following the launching of Sputnik I, the Army-JPL team which had worked -on the Jupiter C missile to test nose cones, was assigned the -responsibility for putting the first United States satellite into orbit -as soon as possible. In just 83 days, a modified Jupiter C launch -vehicle was prepared, an instrumented payload was assembled, a network -of space communications stations was established, and Explorer I was -orbited on January 31, 1958. Explorer was an instrumented assembly -developed by JPL and the State University of Iowa. It discovered the -inner Van Allen radiation belt. - -Subsequently, JPL worked with the Army on other projects to explore -space and to orbit satellites. Among these were Pioneer III, which -located the outer Van Allen Belt, and Pioneer IV, the first U. S. space -probe to reach Earth-escape velocity and to perform a lunar fly-by -mission. - - -GENERAL DYNAMICS: THE ATLAS - -The launch vehicle for Mariner was an Atlas D booster with an Agena B -second stage. Historically, Atlas can be traced to October, 1954, when -the former Convair Corporation (later acquired by General Dynamics) was -invited to submit proposals for research and development of four missile -systems, including a 5,000-mile intercontinental weapon. - -In January, 1946, Convair assigned K. J. Bossart to begin a study of two -proposed types of 5,000-mile missiles: one jet powered at subsonic -speeds, with wings for aerodynamic control; the other a supersonic, -ballistic (wingless and bullet-like), rocket-powered missile capable of -operating outside the Earth’s atmosphere. - - [Illustration: _Photo courtesy of General Dynamics/Astro_ - _Atlas missiles in assembly facility at General - Dynamics/Astronautics plant._] - -This was the beginning of Project MX-774, lineal ancestor of Atlas. -After captive testing at San Diego in 1947, three of the experimental -missiles were test-launched at White Sands Proving Ground in New Mexico. -The first flight failed at 6,200 feet after a premature engine burnout. - -In 1947, the Air Force shelved the MX-774 project. However, this brief -program had proved the feasibility of three concepts later used in -Atlas: swiveling engines for directional control; lightweight, -pressurized airframe structures; and separable nose cones. - -The Korean War stimulated the ICBM concept and, in 1951, a new MX-1593 -contract was awarded to Convair to study ballistic and glide rockets. By -September, 1951, Convair was proposing a ballistic missile that would -incorporate some of the features of the MX-774 design. A plan for an -accelerated program was presented to the Air Force in 1953. After a year -of study, a full go-ahead for the project, now called Atlas, was given -in January, 1955. - -The unit handling the Atlas program was set up as Convair Astronautics, -with J. R. Dempsey as president, on March 1, 1957. - -The first Atlas test flight, in June of 1957, ended in destruction of -the missile when it went out of control. Following another abortive -attempt, the first fully successful flight of an Atlas missile was made -from Cape Canaveral on December 17, 1957. - -The Atlas program was in full swing by 1958, when 14 test missions were -flown. The entire missile was orbited in December, 1958, as Project -Score. It carried the voice of President Eisenhower as a Christmas -message to the world. The Atlas missile system was accepted for field -operations by the Air Force in 1958. - -Also in 1958, an Atlas achieved a new distance record, flying more than -9,000 miles down the Atlantic Missile Range, where it landed in the -Indian Ocean, off the South African coast. - -Atlas has been modified for use by NASA as a space vehicle booster. -Known as the Atlas D, it has launched lunar probes, communications and -scientific Earth satellites, and manned space vehicles. - - -LOCKHEED: AGENA B - -The Lockheed Agena B second-stage vehicle was mounted on top of the -Atlas booster in the launch of the Mariner spacecraft. The U. S. Air -Force had first asked Lockheed Missiles and Space Division, headed by L. -E. Root, to work on an advanced orbital vehicle for both military and -scientific applications in 1956. On October 29 of that year, Lockheed -was appointed prime weapon system contractor on the new Agena Project, -under the Air Force Ballistic Missile Division. In order to speed the -program, the Thor missile was used as the booster stage for the early -Agena flights. The Atlas was also utilized in later operations. - -In August, 1957, the Air Force recommended that the program be -accelerated as much as possible. After Russia orbited Sputnik I in -October of 1957, a further speed-up was ordered. - -The first of the Agena-Discoverer series was launched into orbit on -February 28, 1959, with the Thor missile as the booster. The first -restart in orbit occurred on February 18, 1961, when the new Agena B -configuration was used to put Discoverer XXI into orbit. All of the NASA -missions using Agena, beginning with Ranger I in August, 1961, have been -flown with the B model. - -Agena holds several orbiting records for U. S. vehicles. The first water -recovery followed the 17 orbits of Discoverer XIII on August 11, 1960. -The first air recovery of a capsule from orbit occurred with Discoverer -XIV on August 18, 1960. In all, a total of 11 capsules were recovered -from orbit, 7 in the air, 4 from the sea. - - - - - CHAPTER 3 - THE SPACECRAFT - - -In the 11 brief months which JPL had to produce the Mariner spacecraft -system, there was no possibility of designing an entirely new -spacecraft. JPL’s solution to the problem was derived largely from the -Laboratory’s earlier space exploration vehicles, such as the Vega, the -Ranger lunar series, and the cancelled Mariner A. - -Wherever possible, components and subsystems designed for these projects -were either utilized or redesigned. Where equipment was purchased from -industrial contractors, existing hardware was adapted, if practicable. -Only a minimum of testing could be performed on newly designed equipment -and lengthy evaluation of “breadboard” mock-ups was out of the question. - -Ready for launch, the spacecraft measured 5 feet in diameter and 9 feet -11 inches in height. With the solar panels and the directional antenna -unfolded in the cruise position, Mariner was 16 feet 6 inches wide and -11 feet 11 inches high. - - -THE SPACEFRAME - -The design engineers were forced to work within the framework of the -earlier spacecraft technology because of the time restrictions, but -Mariner I and II could weigh only about half as much as the Ranger -spacecraft and just over one-third as much as the planned Mariner A. - - [Illustration: _Mariner spacecraft with solar panels, microwave - radiometer, and directional antenna extended in flight position. - Principal components are shown._] - - ROLL AXIS - OMNIANTENNA - MAGNETOMETER SENSOR - PARTICLE FLUX DETECTORS (GEIGER TUBES) - RADIOMETER REFERENCE HORNS - MICROWAVE RADIOMETER - INFRARED RADIOMETER - ION-CHAMBER - COSMIC DUST DETECTOR - EARTH SENSOR - SOLAR PANEL - COMMAND ANTENNA - SOLAR SAIL - ATTITUDE CONTROL GAS BOTTLES - SOLAR PLASMA DETECTOR - DIRECTIONAL ANTENNA - -The basic structural unit of Mariner was a hexagonal frame made of -magnesium and aluminum, to which was attached an aluminum -superstructure, a liquid-propelled rocket engine for midcourse -trajectory correction, six rectangular chassis mounted one on each face -of the hexagonal structure, a high-gain directional antenna, the Sun -sensors, and gas jets for control of the spacecraft’s attitude. - -The tubular, truss-type superstructure extended upward from the base -hexagon. It provided support for the solar panels while latched under -the shroud during the launch phase, and for the radiometers, the -magnetometer, and the nondirectional antenna, which was mounted at the -top of the structure. The superstructure was designed to be as light as -possible, yet be capable of withstanding the predicted load stresses. - -The six magnesium chassis mounted to the base hexagon housed the -following equipment: the electronics circuits for the six scientific -experiments, the communications system electronics; the data encoder -(for processing data before telemetering it to the Earth) and the -command electronics; the attitude control, digital computer, and timing -sequencer circuits; a power control and battery charger assembly; and -the battery assembly. - -The allotment of weights for Mariner II forced rigid limitation in the -structural design of the spacecraft. As launched, the weights of the -major spacecraft subsystems were as follows: - - Structure 77 pounds - Solar panels 48 pounds - Electronics 146 pounds - Propulsion 32 pounds - Battery 33 pounds - Scientific experiments 41 pounds - Miscellaneous equipment 70 pounds - Gross weight 447 pounds - - -THE POWER SYSTEM - -Mariner II was self-sufficient in power. It converted energy from -sunlight into electrical current through the use of solar panels -composed of photoelectric cells which charged a battery installed in one -of the six chassis on the hexagonal base. The control, switching, and -regulating circuits were housed in another of the chassis cases. - - [Illustration: _This hexagonal frame, constructed of magnesium and - aluminum, is the basic supporting structure around which the Mariner - spacecraft is assembled._] - - [Illustration: _Plan view from top showing six magnesium chassis - hinged in open position._] - - VIEW LOOKING AFT ASSEMBLIES HINGED IN OPEN POSITION - SCIENTIFIC EQUIPMENT ASSEMBLY I - COMMUNICATIONS ASSEMBLY II - DATA ENCODER AND COMMAND ASSEMBLY III - ATTITUDE CONTROL AND CC AND S ASSEMBLY IV - POWER ASSEMBLY V - BATTERY ASSEMBLY VI - -The battery operated the spacecraft systems during the period from -launch until the solar panels were faced onto the Sun. In addition, the -battery supplied power during trajectory maneuvers when the panels were -temporarily out of sight of the Sun. It shared the demand for power when -the panels were overloaded. The battery furnished power directly for -switching various equipment in flight and for certain other heavy loads -of brief duration, such as the detonation of explosive devices for -releasing the solar panels. - - [Illustration: _Mariner spacecraft with solar panels in open - position. Note extension to left panel to balance solar pressures in - flight._] - -The Mariner battery used sealed silver-zinc cells and had a capacity of -1000 watt-hours. It weighed 33 pounds and was recharged in flight by the -solar panels. - -The solar panels, as originally designed, were 60 inches long by 30 -inches wide and contained approximately 9800 solar cells in a total area -of 27 square feet. Each solar cell produced only about 230 -one-thousandths of a volt. The entire array was designed to convert the -Sun’s energy to electrical power in the range between 148 and 222 watts. -When a later design change required the extension of one panel in order -to add more solar cells, it was necessary to add a blank extension to -the other panel in order to balance the solar pressure on the -spacecraft. - -In order to protect the solar cells from the infrared and ultraviolet -radiation of the Sun, which would produce heat but no electrical energy, -each cell was shielded from these rays by a glass filter which was -nevertheless transparent to the light which the cells converted into -power. - -The power subsystem electronics circuits were housed in another of the -hexagon chassis cases. This equipment was designed to receive and switch -power either from the solar panels, the battery, or a combination of the -two, to a booster-regulator. - - -CC&S: THE BRAIN AND THE STOPWATCH - -Once the Atlas booster lifted Mariner off the launch pad, the digital -Central Computer and Sequencer (CC&S) performed certain computations and -provided the basic timing control for those spacecraft subsystems which -required a sequenced programming control. - -The CC&S was designed to initiate the operations of the spacecraft in -three distinct sequences or “modes”: (1) the launch mode, from launch -through the cruise configuration; (2) the midcourse propulsion mode, -when Mariner readjusted its sights on Venus; and (3) the encounter mode, -involving commands for data collection in the immediate vicinity of the -planet. - -The CC&S timed Mariner’s actions as it travelled more than 180 million -miles in pursuit of Venus. A highly accurate electronic clock -(crystal-controlled oscillator) scheduled the operations of the -spacecraft subsystems. The oscillator frequency of 307.2 kilocycles was -reduced to the 2,400- and 400-cycle-per-second output required for the -power subsystem. - -The control oscillator also timed the issuance of commands by the CC&S -in each of the three operating modes of the spacecraft. - -A 1-pulse-per-minute signal was provided for such launch sequence events -as the extension of the solar panels 44 minutes after launch, turning on -power for the attitude control subsystem one hour after launch, and for -certain velocity correction commands during the midcourse maneuver. - - [Illustration: _The spacecraft used two antennas for communication. - The omni-antenna (top) was utilized when the directional antenna - (bottom) could not be pointed at the Earth._] - - [Illustration: _This command antenna (on solar panel) was used to - receive maneuver commands._] - -A 1-pulse-per-second signal was generated as a reference during the roll -and pitch maneuvers in the midcourse trajectory correction phase. One -pulse was generated every 3.3 hours in order to initiate the command to -orient the directional antenna on the Earth at 167 hours after launch. - -Finally, one pulse every 16.7 hours was used to readjust the -Earth-oriented direction of the antenna throughout the flight. - - -TELECOMMUNICATIONS: RELAYING THE DATA - -The telecommunications subsystem enabled Mariner to receive and to -decode commands from the Earth, to encode and to transmit information -concerning space and Mariner’s own functioning, and to provide a means -for precise measurement of the spacecraft’s velocity and position -relative to the Earth. The spacecraft accomplished all these functions -using only 3 watts of transmitted power up to a maximum range of 53.9 -million miles. - -A data encoder unit, with CC&S sequencing, timed the three phases of -Mariner’s journey: (1) In the launch mode, only engineering data on -spacecraft performance were transmitted; (2) during the cruise mode, -information concerning space and Mariner’s own functioning was -transmitted; and (3) while the spacecraft was in the vicinity of Venus, -only scientific information concerning the planet was to be transmitted. -(The CC&S failed to start the third mode automatically and it was -initiated by radio command from the Earth.) After the encounter with -Venus, Mariner was programmed to switch back to the cruise mode for -handling both engineering and science data (this sequence was also -commanded by Earth radio). - -Mariner II used a technique for modulating (superimposing intelligent -information) its radio carrier with telemetry data known as phase-shift -keying. In this system, the coded signals from the telemetry -measurements displace another signal of the same frequency but of a -different phase. These displacements in phase are received on the Earth -and then translated back into the codes which indicate the voltage, -temperature, intensity, or other values measured by the spacecraft -telemetry sensors or scientific instruments. - -A continually repeating code, almost noise-like both in sound and -appearance on an oscilloscope, was used for synchronizing the ground -receiver decoder with the spacecraft. This decoder then deciphered the -data carried on the information channel. - -This technique was called a two-channel, binary-coded, pseudo-noise -communication system and it was used to modulate a radio signal for -transmission, just as in any other radio system. - -Radio command signals transmitted to Mariner were decoded in a command -subassembly, processed, and routed to the proper using devices. A -transponder was used to receive the commands, send back confirmation of -receipt to the Earth, and distribute them to the spacecraft subsystems. - -Mariner II used four antennas in its communication system. A cone-like -nondirectional (omni) antenna was mounted at the top of the spacecraft -superstructure, and was used from injection into the Venus flight -trajectory through the midcourse maneuver (the directional antenna could -not be used until it had been oriented on the Earth). - -A dish-type, high-gain, directional antenna was used at Earth -orientation and after the trajectory correction maneuver was completed. -It could receive radio signals at greater distances than the -nondirectional antenna. The directional antenna was nested beneath the -hexagonal frame of the spacecraft while it was in the nose-cone shroud. -Following the unfolding of the solar panels, it was swung into operating -position, although it was not used until after the spacecraft locked -onto the Sun. - -The directional antenna was equipped with flexible coaxial cables and a -rotary joint. It could move in two directions; one motion was supplied -by rolling the spacecraft around its long axis. - -In addition, two command antennas, one on either side of one of the -solar panels, received radio commands from the Earth for the midcourse -maneuver and other functions. - - -ATTITUDE CONTROL: BALANCING IN SPACE - -Mariner II had to maintain a delicate balance in its flight position -during the trip to Venus (like a tight-wire walker balancing with a -pole) in order to keep its solar panels locked onto the Sun and the -directional antenna pointed at the Earth. Otherwise, both power and -communications would have been lost. - -A system of gas jets and valves was used periodically to adjust the -attitude or position of the spacecraft. Expulsion of nitrogen gas -supplied the force for these adjustments during the cruise mode. While -the spacecraft was subjected to the heavier disturbances caused by the -rocket engine during the midcourse maneuver, the gas jets could not -provide enough power to control the attitude of the spacecraft and it -was necessary to use deflecting vanes as rudders in the rocket engine -exhaust stream for stabilizing purposes. - -The attitude control system was activated by CC&S command 60 minutes -after launching. It operated first to align the long axis of the -spacecraft with the Sun; thus its solar panels would face the Sun. -Either the Sun sensors or the three gyroscopes mounted in the pitch -(rocking back and forth), yaw (side to side), and roll axes, could -activate the gas jet valves during the maneuver, which normally required -about 30 minutes to complete. - -The spacecraft was allowed a pointing error of 1 degree in order to -conserve gas. The system kept the spacecraft swinging through this 1 -degree of arc approximately once each 60 minutes. As it neared the limit -on either side, the jets fired for approximately ¹/₅₀ of a second to -start the swing slowly in the other direction. Thus, Mariner rocked -leisurely back and forth throughout its 4-month trip. - -Sensitive photomultiplier tubes or electric eyes in the Earth sensor, -mounted on the directional antenna, activated the gas jets to roll the -spacecraft about the already fixed long axis in order to face the -antenna toward the Earth. When the Earth was “acquired,” the antenna -would then necessarily be oriented in the proper direction. If telemetry -revealed that Mariner had accidentally fixed on the Moon, over-ride -radio commands from the Earth could restart the orientation sequence. - - -PROPULSION SYSTEM - -The Mariner propulsion system for midcourse trajectory correction -employed a rocket engine that weighed 37 pounds with fuel and a nitrogen -pressure system, and developed 50 pounds of thrust for a maximum of 57 -seconds. The system was suspended within the central portion of the -basic hexagonal structure of the spacecraft. - -This retro-rocket engine used a type of liquid propellant known as -anhydrous hydrazine and it was so delicately controlled that it could -burn for as little as ²/₁₀ of a second and increase the velocity of the -spacecraft from as little as ⁷/₁₀ of a foot per second to as much as 200 -feet per second. - -The hydrazine fuel was stored in a rubber bladder inside a -doorknob-shaped container. At the ignition command, nitrogen gas under -3,000-pound-per-square-inch pressure was forced into the propellant tank -through explosively activated valves. The nitrogen then squeezed the -rubber bladder, forcing the hydrazine into the combustion chamber. - - [Illustration: _The midcourse propulsion system provides trajectory - correction for close approach to Venus._] - - FUEL TANK - NITROGEN TANK - JET VANE ACTUATOR (ONE OF FOUR) - THRUST CHAMBER - -Hydrazine, a monopropellant, requires a starting ignition for proper -combustion. In the Mariner system, nitrogen tetroxide starting or -“kindling” fluid was injected into the propellant tank by a pressurized -cartridge. Aluminum oxide pellets in the tank acted as catalysts to -control the speed of combustion of the hydrazine. The burning of the -hydrazine was stopped when the flow of nitrogen gas was halted, also by -explosively activated valves. - - -TEMPERATURE CONTROL - -Mariner’s 129 days in space presented some unique problems in -temperature control. Engineers were faced with the necessity of -achieving some form of thermal balance so that Mariner would become -neither too hot nor too cold in the hostile environment of space. - -The spacecraft’s temperature control system was made as thermally -self-sufficient as possible. Paint patterns, aluminum sheet, thin gold -plating, and polished aluminum surfaces reflected and absorbed the -proper amount of heat necessary to keep the spacecraft and its -subsystems at the proper operating temperatures. - -Thermal shields were used to protect the basic hexagon components. The -upper shield, constructed of aluminized plastic on a fiberglass panel, -protected the top of the basic structure and was designed for maximum -immunity to ultraviolet radiation. The lower shield was installed below -the hexagon; it was made of aluminum plastic faced with aluminum foil -where it was exposed to the blast of the midcourse rocket engine -exhaust. - - [Illustration: _Methods used to control the temperature of the - Mariner spacecraft in flight._] - - CHROMATE CONVERSION COATING - UPPER THERMAL SHIELD - POLISHED ALUMINUM - LOUVERS - GOLD PLATE - BLACK PAINT - LOWER THERMAL SHIELD - WHITE PAINT - -The six electronics cases on the hexagon structure were variously -treated, depending upon the power of the components contained in each. -Those of high power were coated with a good radiating surface of white -paint; assemblies of low power were provided with polished aluminum -shields to minimize the heat loss. - -The case housing the attitude control and CC&S electronics circuits was -particularly sensitive because the critical units might fail above 130 -degrees F. A special assembly was mounted on the face of this case; it -consisted of eight movable, polished aluminum louvers, each actuated by -a coiled, temperature-sensitive, bimetallic element. When the -temperature rose, the elements acted as springs and opened the louvers. -A drop in temperature would close them. - -Structures and bracket assemblies external to the basic hexagon were -gold plated if made of magnesium, or polished if aluminum. Thus -protected, these items became poor thermal radiators as well as poor -solar absorbers, making them relatively immune to solar radiation. -External cabling was wrapped in aluminized plastic to produce a similar -effect. - -The solar panels were painted on the shaded side for maximum radiation -control properties. Other items were designed so that the internal -surfaces were as efficient radiators as possible, thus conserving the -spacecraft’s heat balance. - - -THE SCIENTIFIC INSTRUMENTS - -Four instruments were operated throughout the cruise and encounter modes -of Mariner: a magnetometer, a solar plasma detector, a cosmic dust -detector, and a combined charged-particle detector and radiation -counter. Two radiometers were used only in the immediate vicinity of -Venus. - -These instruments are described in detail in Chapter 8. - - - - - CHAPTER 4 - THE LAUNCH VEHICLE - - -The motive power of Mariner itself was limited to a trajectory -correction rocket engine and an ability, by means of gas jets, to keep -its two critical faces pointing at the Sun and the Earth. Therefore, the -spacecraft had to be boosted out of the Earth’s gravitational field and -injected into a flight path accurate enough to allow the trajectory -correction system to alter the course to deliver the spacecraft close -enough to Venus to be within operating range of the scientific -instruments. - -The combined Atlas-Agena B booster system which was selected to do the -job had a total thrust of about 376,000 pounds. With this power, -Atlas-Agena could put 5,000 pounds of payload into a 345-mile orbit, -propel 750 pounds on a lunar trajectory, or launch approximately 400 -pounds on a planetary mission. This last capability would be taxed to -the limit by the 447 pounds of the Mariner spacecraft. - - -THE ATLAS BOOSTER: POWER OF SIX 707’S - -The 360,000 pounds of thrust developed by the Atlas D missile is -equivalent to the thrust generated by the engines of six Boeing 707 jet -airplanes. All of this awesome power requires a gargantuan amount of -fuel: in less than 20 seconds, Atlas consumes more than a -propeller-driven, four-engine airplane burns in flying coast-to-coast -nonstop. - - [Illustration: _Photo courtesy of General Dynamics/Astronautics_ - _This military version of the Atlas missile is modified for NASA - space flights._] - -The Atlas missile, as developed by Convair for the Air Force, has a -range of 6,300 miles and reaches a top speed of 16,000 miles per hour. -The missile has been somewhat modified for use by NASA as a space -booster vehicle. Its mission was to lift the second-stage Agena B and -the Mariner spacecraft into the proper position and altitude at the -right speed so that the Agena could go into Earth orbit, preliminary to -the takeoff for interplanetary space. - -The Atlas D has two main sections: a body or sustainer section, and a -jettisonable aft, or booster engine section. The vehicle measures about -100 feet in length (with military nose cone) and has a diameter of 10 -feet at the base. The weight is approximately 275,000 pounds. - -No aerodynamic control surfaces such as fins or rudders are used. The -Atlas is stabilized and controlled by “gimbaling” or swiveling the -engine thrust chambers by means of a hydraulic system. The direction of -thrust can thus be altered to control the movements of the missile. - -The aft section mounts two 154,500-pound-thrust booster engines and the -entire section is jettisoned or separated from the sustainer section -after the booster engines burn out. The 60,000-pound-thrust sustainer -engine is attached at the center line of the sustainer section. Two -1,000-pound-thrust vernier (fine steering) engines are installed on -opposite sides of the tank section in the yaw or side-turn plane. - -All three groups of engines operate during the booster phase. Only the -sustainer and the vernier engines burn after staging (when the booster -engine section is separated from the sustainer section of the missile). - -All of the engines use liquid oxygen and a liquid hydrocarbon fuel -(RP-1) which is much like kerosene. Dual turbopumps and valves control -the flow of these propellants. The booster engine propellants are -delivered under pressure to the propellant or combustion chamber, where -they are ignited by electroexplosive devices. Each booster thrust -chamber can be swiveled a maximum of 5 degrees in pitch (up and down) -and yaw (from side to side) about the missile centerline. - -The sustainer engine is deflected 3 degrees in pitch and yaw. The -outboard vernier engines gimbal to permit pitch and roll movement -through 140 degrees of arc, and yaw movement through 20 degrees toward -the missile body and 30 degrees outward. - -All three groups of engines are started and develop their full rated -thrust while the missile is held on the launch pad. After takeoff, the -booster engines burn out and are jettisoned. The sustainer engine -continues to burn until its thrust is terminated. The swiveled vernier -engines provide the final correction in velocity and missile attitude -before they are also shut down. - -The propellant tank is the basic structure of the forward or sustainer -section of the Atlas. It is made of thin stainless steel and is -approximately 50 feet long. Internal pressure of helium gas is used to -support the tank structure, thus eliminating the need for internal -bracing structures, saving considerable weight, and increasing over-all -performance of the missile. The helium gas used for this purpose is -expanded to the proper pressure by heat from the engines. - -Equipment pods on the outside of the sustainer section house the -electrical and electronic units and other components of the missile -systems. - -The Atlas uses a flight programmer, an autopilot, and the gimbaled -engine thrust chamber actuators for flight control. The attitude of the -vehicle is controlled by the autopilot, which is set for this automatic -function before the flight. Guidance commands are furnished by a ground -radio guidance system and computer. - -The airborne radio inertial guidance system employs two radio beacons -which respond to the ground radar. A decoder on board the missile -processes the guidance commands. - - -THE AGENA B: START AND RESTART - -Launching Mariner to Venus required a second-stage vehicle capable of -driving the spacecraft out of Earth orbit and into a proper flight path -to the planet. - - [Illustration: _Photo courtesy of Lockheed Missiles and Space - Company_ - _The Agena B second stage is hoisted to the top of the gantry at - AMR._] - -The Agena B used for this purpose weighs 1,700 pounds, is 60 inches in -diameter, and has an over-all length of 25 feet, varying somewhat with -the payload. The Agena B fuel tanks are made of 0.080-inch aluminum -alloy. - -The liquid-burning engine develops more than 16,000 pounds of thrust. -The propellants are a form of hydrazine and red fuming nitric acid. - -The Agena can be steered to a desired trajectory by swiveling the -gimbal-mounted engine on command of the guidance system. The attitude of -the vehicle is controlled either by gimbaling the engine or by ejecting -gas from pneumatic thrusters. - -The Agena has the ability to restart its engine after it has already -fired once to reach an Earth orbital speed. This feature makes possible -a significant increase in payload and a change of orbital altitude. A -velocity meter ends the first and second burns when predetermined -velocities have been reached. - -After engine cutoff, the major reorientation of the vehicle is achieved -through gas jets controlled from an electronic programming device. This -system can turn the Agena completely around in orbit, or pitch it down -for reentry into the atmosphere. The attitude is controlled by an -infrared, heat-sensitive horizon scanner and gyroscopes. - -The principal modification to the Agena vehicle for the Mariner II -mission was an alteration to the spacecraft-Agena adapter in order to -reduce weight. - - - - - CHAPTER 5 - FLIGHT INTO SPACE - - -With the Mariner R Project officially activated in the fall of 1961 and -the launch vehicles selected, engineers proceeded at full speed to meet -the difficult launch schedule. - -A preliminary design was adopted in late September, when the scientific -experiments to be carried on board were also selected. By October 2, a -schedule had been established that would deliver two spacecraft to the -assembly building in Pasadena by January 15 and 29, 1962, respectively, -with the spares to follow in two weeks. - -During the week of November 6, tests were underway to determine problems -involved in mating a mock-up of the spacecraft with the Agena shroud and -adapter assembly. A thermal control model of the spacecraft had already -gone into the small space simulator at JPL for preliminary temperature -tests. - -MR-1, the first Mariner scheduled for flight, was in assembly -immediately after January 8, 1962, and the process was complete by the -end of the month, when electrical and magnetic field tests had been -started. At the same time, assembly of MR-2 was underway. Work on MR-1 -was a week ahead of schedule by the end of the month. - -A full-scale temperature control model of the spacecraft went into the -large space simulator on February 26. In mid-March, system tests began -on both spacecraft and it was decided that the flight hardware would be -tested only in the small simulator, with the temperature control model -continuing in the large chamber. - - [Illustration: _Technician wears hood and protective goggles while - working on Mariner spacecraft in Space simulator chamber at Jet - Propulsion Laboratory, Pasadena._] - -On March 26, MR-1 was subjected to full-scale mating tests with the -shroud (cover) and the adapter for mounting the spacecraft on top of the -Agena. MR-2 was undergoing vibration tests during the week of April 16. -By April 30, MR-1 had completed vibration tests and had been mapped for -magnetic fields so that, once compensated for, they would not interfere -with the magnetometer experiment in space. - -A dummy run of MR-1 was conducted on May 7 and the spacecraft, space -flight center, and computing equipment were put through a simulated -operations test run during the same week. - -By May 14, clean-up and final inspection by microscope had begun on -MR-1, MR-2, and MR-3 (the latter spacecraft had been assembled from the -spares). Soon after, the first two van loads of equipment were shipped -to Cape Canaveral. The final system test of MR-1 was completed on May 21 -and the test of MR-2 followed during the same week. - -During the week of May 28, all three spacecraft and their associated -ground support equipment were packed, loaded, and shipped to the -Atlantic Missile Range (AMR). At the same time, the Atlas designated to -launch MR-1 went aboard a C-133 freight aircraft at San Diego. On the -same day, an Air Force order grounded all C-133’s for inspection and the -plane did not depart until June 9. - -By June 11, 1962, the firing dates had been established and both -spacecraft were ready for launching. The Atlas booster had already been -erected on the launch pad. The dummy run and a joint flight acceptance -test were completed on MR-1 during the week of July 2. Final flight -preparations and system test of MR-1 and the system test of MR-2 were -concluded a week later. - -Thus, in 324 days, a new spacecraft project had been activated; the -design, assembly, and testing had been completed; and the infinite -number of decisions pertaining to launch, AMR Range Operations, -deep-space tracking, and data processing activities had been made and -implemented. - -Venus was approaching the Earth at the end of its 19-month excursion -around the Sun. The launch vehicles and Mariners I and II stood ready to -go from Canaveral’s Launch Complex 12. The events leading to the first -close-up look at Venus and intervening space were about to reach their -first crisis: a fiery explosion over the Atlantic Ocean. - - -MARINER I: AN ABORTIVE LAUNCH - -After 570 hours of testing, Mariner I was poised on top of the -Atlas-Agena launch vehicle during the night of July 20, 1962. The time -was right, the Range and the tracking net were standing by, the launch -vehicles were ready to cast off the spacecraft for Venus. - - [Illustration: _Atlas for launching Mariner II arrives at Cape - Canaveral in C-133 aircraft._] - -The countdown was begun at 11:33 p.m., EST, July 20, after several -delays because of trouble in the Range Safety Command system. At the -time, the launch count stood at T minus 176 minutes—if all went well, -176 minutes until the booster engines were ignited. - -Another hold again delayed the count until 12:37 a.m., July 21, when -counting was resumed at T minus 165 minutes. The count then proceeded -without incident to T minus 79 minutes at 2:20 a.m., when uncertainty -over the cause of a blown fuse in the Range Safety circuits caused the -operations to be “scrubbed” or cancelled for the night. The next launch -attempt was scheduled for July 21-22. - -The second launch countdown for Mariner I began shortly before midnight, -July 21. Spacecraft power had been turned on at 11:08 p.m., with the -launch count at T minus 200 minutes. At T minus 135 minutes, the weather -looked good. A 41-minute hold was required at minus 130 minutes (12:17 -a.m., July 22) in order to change a noisy component in the ground -tracking system. - -When counting was resumed at T minus 130 minutes, the clock read 12:48 -a.m. A previously scheduled hold was called at T minus 60 minutes, -lasting from 1:58 to 2:38 a.m. The good weather still held. - -At T minus 80 seconds, power fluctuations in the radio guidance system -forced a 34-minute hold. Time was resumed at 4:16 a.m., when the -countdown was set back to T minus 5 minutes. - -At exactly 4:21.23 a.m., EST, the Atlas thundered to life and lifted off -the pad, bearing its Venus-bound load. The boost phase looked good until -the Range Safety officer began to notice an unscheduled yaw-left -(northeast) maneuver. By 4:25 a.m., it was evident that, if allowed to -continue, the vehicle might crash in the North Atlantic shipping lanes -or in some inhabited area. Steering commands were being supplied but -faulty application of the guidance equations was taking the vehicle far -off course. - -Finally, at 4:26.16 a.m., after 293 seconds of flight and with just 6 -seconds left before separation of the Atlas and Agena—after which the -launch vehicle could not be destroyed—a Range Safety officer hit the -“destruct” button. - -A flash of light illuminated the sky and the choppy Atlantic waters were -awash with the glowing death of a space probe. Even as it fluttered down -to the sea, however, the radio transponder of the shattered Mariner I -continued to transmit for 1 minute and 4 seconds after the destroy -command had been sent. - -Mariner I did not succumb easily. - - -MARINER II: A ROLL BEFORE PARKING - -Ever since Mariner II had arrived at the Cape on June 4, test teams of -all organizations had labored day and night to prepare the spacecraft -for launch. The end of their efforts culminated after some 690 hours of -test time, both in California and in Florida. - -Thirty-five days after Mariner I met its explosive end, the first -countdown on Mariner II was underway. At 6:43 p.m., EST, August 25, -1962, time was picked up. The countdown did not proceed far, however. -The Atlas crew asked for a hold at T minus 205 minutes (8:39 p.m.) -because of stray voltages in the command destruct system caused by a -defective Agena battery. After considerable delay, the launch effort was -scrubbed at 10:06 p.m. - - [Illustration: _Two assembly operations and system checkouts are - performed separated by a trip to the pad to verify compatibility - with the launch vehicle_] - - [Illustration: _A complete electronic checkout station in the hangar - supports the spacecraft to ensure operability_] - - [Illustration: _Mariner takes form as the solar panels are attached - and the final hangar checkout operations are performed before the - launch._] - - [Illustration: _Wrapped in a dust cover, the spacecraft is - transferred from Hangar AE at AMR to the explosive safe area for - further tests._] - - [Illustration: _Inside the bunker-like explosive safe area, the - powerful midcourse maneuver rocket engine is installed in the center - of the spacecraft._] - - [Illustration: _Final assembly and inspection complete, Mariner is - “canned” in the nose shroud that will protect it through the Earth’s - atmosphere and into space._] - - [Illustration: _At the pad, the shrouded spacecraft is lifted past - the Atlas ..._] - - [Illustration: _... and the Agena._] - - [Illustration: _Twelfth floor: Mariner reaches its mating level._] - - [Illustration: _The spacecraft is eased over to the top of the Agena - ..._] - - [Illustration: _... and carefully mated to it._] - -The second launch attempt started at 6:37 p.m., August 26, with the -Atlas-Agena B and Mariner II ready on the pad. At 9:52 p.m., T minus 100 -minutes, a 40-minute hold was called to replace the Atlas main battery. -By 10:37, with 95 minutes to launch, all spacecraft systems were ready -to go. - -A routine hold at T minus 60 minutes was extended beyond 30 minutes in -order to verify the spacecraft battery life expectation. At 11:48 p.m., -with the count standing at T minus 55 minutes, the spacecraft, the -vehicles, the Range, and the DSIF were all given the green light. - -When good launching weather was reported at 12:18 a.m., August 27, just -25 minutes from liftoff, a cautious optimism began to mount in the -blockhouse and among the tired crews. - -But the tension began to build again. The second prescheduled hold at T -minus 5 minutes was extended beyond a half-hour when the radio guidance -system had difficulty with ground station power. Counting was “picked -up” and the clock continued to move down to 60 seconds before liftoff. - -Suddenly, the radio guidance system was in trouble again. Fluctuations -showed in its rate beacon signals, and another hold was called. Still -another hold for the same reason followed at T minus 50 seconds. This -time, at 1:30 a.m., the count was set back to T minus 5 minutes. - -One further crisis developed during this hold—only 3 minutes of -pre-launch life remained in Atlas’ main battery. A quick decision was -made to hold the switchover to missile power until T minus 60 seconds to -help conserve the life of the battery. - -At 1:48 a.m., the count was resumed again at T minus 5 minutes. The long -seconds began to drag. Finally, the Convair test director pressed the -fire button. - -Out on the launch pad, the Atlas engines ignited with a white puff and -began to strain against the retaining bolts as 360,000 pounds of thrust -began to build up. In a holocaust of noise and flame, the Atlas was -released and lifted off the launch pad on a bearing of 106.8 degrees at -exactly 1 hour, 53 minutes, 13.927 seconds in the morning of August 27, -1962. - -Mariner II was on its way to listen to the music of the spheres. - -As the launch vehicle roared up into the night sky, the JPL Launch -Checkout Station (DSIF O) tracked the spacecraft until Mariner -disappeared over the horizon. A quick, preliminary evaluation of -spacecraft data showed normal readings and Atlas seemed to be flying a -true course. The AMR in-flight data transmission and computational -operations were being performed as expected. With liftoff out of the -way, the launch began to look good. - -After the radio signal from the ground guidance system cut off the -engines and the booster section was jettisoned, the remaining Atlas -forward section, plus the Agena and the spacecraft began to roll. -However, it stabilized itself in a normal attitude. Although the Atlas -had not gone out of the Range Safety restrictions, it was within just 3 -degrees of exceeding the Agena horizon sensor limits, which would have -forced another aborted mission. - -After the booster separation, the Atlas sustainer and vernier engines -continued to burn until they were shut off by radio guidance command. -Shortly thereafter, spring-loaded bolts ejected the nose-cone shroud -which had protected the spacecraft against frictional heating in the -atmosphere. Simultaneously, the gyroscopes in the Agena were started -and, at about 1:58 a.m., the Agena and the spacecraft separated from the -now-spent Atlas, which was retarded by small retro-rockets and drifted -back into the atmosphere, where it was destroyed by friction on reentry. - - -THE PARKING ORBIT - -As the Agena separated from the Atlas booster vehicle, it was programmed -to pitch down almost 15 degrees, putting it roughly parallel with the -local horizon. Then, following a brief coasting period, the Agena engine -ignited at 1:58.53 a.m. and fired until 2:01.12 a.m. Cut-off occurred at -a predetermined value of velocity. Both the Agena and the spacecraft had -now reached a speed of approximately 18,000 miles per hour and had gone -into an Earth orbit at an altitude of 116.19 statute miles. - -The second stage and the spacecraft were now in a “parking orbit,” which -would allow the vehicle to coast out to a point more favorable than Cape -Canaveral for blasting off Mariner for Venus. - -During the launch, Cape radar had tracked the radar beacon on the Agena, -losing it on the horizon at 2:00.53 a.m. Radar stations at Grand Bahama -Island, San Salvador, Ascension, the Twin Falls Victory ship, and -Pretoria (in South Africa) continued to track down range. Meanwhile, -Antigua had “locked on” and tracked the spacecraft’s radio transponder -and telemetry from 1:58 to 2:08 a.m. when it went over the Antigua -horizon. - - [Illustration: _Mariner II is accelerated to Earth-escape velocity - and out of orbit near St. Helena. Rotation of earth causes flight - path to appear to double back to west over Africa._] - - [Illustration: _The sequence of events in the launch phase of the - Mariner flight to Venus._] - - EVENT - 1. LIFTOFF - 2. ATLAS BOOSTER ENGINE CUTOFF - 3. ATLAS SUSTAINER ENGINE CUTOFF - 4. ATLAS VERNIER ENGINE CUTOFF - 5. SPACECRAFT SHROUD EJECTION - 6. ATLAS-AGENA B SEPARATION - 7. AGENA B FIRST IGNITION - 8. AGENA B FIRST CUTOFF - 9. AGENA B SECOND IGNITION - 10. AGENA B SECOND CUTOFF - 11. SPACECRAFT SEPARATION - 12. INITIATE AGENA YAW MANEUVER - 13. COMPLETE AGENA YAW MANEUVER - 14. EXPEL UNUSED AGENA PROPELLANT - -The second coasting period lasted 16.3 minutes, a time determined by the -ground guidance computer and transmitted to the Agena during the vernier -burning period of Atlas. Then, Agena restarted its engine and fired for -a second time. At the end of this firing period, both the Agena and -Mariner, still attached, had been injected into a transfer trajectory to -Venus at a velocity exceeding that required to escape from the Earth’s -gravity. - -The actual injection into space occurred at 26 minutes 3.08 seconds -after liftoff from the Cape (2:19.19 a.m., EST) at a point above 14.873 -degrees south latitude and 2.007 degrees west longitude. Thus, Mariner -made the break for Venus about 360 miles northeast of St. Helena, 2,500 -miles east of the Brazilian coast, and about 900 miles west of Angola on -the west African shore. - -During injection, the vehicle was being tracked by Ascension, telemetry -ship Twin Falls Victory, and Pretoria. Telemetry ship Whiskey secured -the spacecraft signal just after injection and tracked until 2:26 a.m. -Pretoria began its telemetry track at 2:21 and continued to track for -almost two hours, until 4:19 a.m. - -Injection velocity was 7.07 miles per second or 25,420 miles per hour, -just beyond Earth-escape speed. The distance at the time of injection -from Canaveral’s Launch Complex 12 was 4,081.3 miles. - -The Agena and Mariner flew the escape path together for another two -minutes after injection before they were separated at 2:21 a.m. Agena -then performed a 140-degree yaw or retro-turn maneuver by expelling -unused propellants. The purpose was to prevent the unsterilized Agena -from possibly hitting the planet, and from following Mariner too closely -and perhaps disturbing its instruments. - -Now, Mariner II was flying alone and clear. Ahead lay a journey of 109 -days and more than 180 million miles. - - -ORIENTATION AND MIDCOURSE MANEUVER - -As Mariner II headed into space, the Deep Space Instrumentation Facility -(DSIF) network began to track the spacecraft. At 2:23.59 a.m., DSIF 5 at -Johannesburg, aided by the Mobile Tracking Station, installed in vans in -the vicinity, was “looking” at the spacecraft, just four minutes after -injection. - -Johannesburg was able to track Mariner until 4:04 p.m. because, as the -trajectory took Mariner almost radially away from the Earth, our planet -began in effect to turn away from under the spacecraft. On an Earth map, -because of its course and the rotation of the Earth, Mariner II appeared -to describe a great arc over the Indian Ocean far to the west of -Australia, then to turn north and west and to proceed straight west over -south-central Africa, across the Atlantic, and over the Amazon Basin of -northern South America. Johannesburg finally lost track at a point over -the middle of South America. - -While swinging over the Indian Ocean on its first pass, the spacecraft -was acquired by Woomera’s DSIF 4 at 2:42.30 a.m., and tracked until 8:08 -a.m., when Mariner was passing just to the north of Madagascar on a -westerly course. Goldstone did not acquire the spacecraft until it was -approaching the east coast of South America at 3:12 p.m., August 27. - -With Mariner slowly tumbling in free space, it was now necessary to -initiate a series of events to place the spacecraft in the proper flight -position. At 2:27 a.m., 44 minutes after launch, the Mariner Central -Computer and Sequencer (CC&S) on board the spacecraft issued a command -for explosively activated pin pullers to release the solar panels and -the radiometer dish from their launch-secured positions. At 2:53, 60 -minutes after liftoff, the attitude control system was turned on and the -Sun orientation sequence began with the extension of the directional -antenna to a preset angle of 72 degrees. - - [Illustration: _Mariner II was launched while Venus was far behind - the Earth. During the 109-day flight, Venus overtook and passed the - Earth. It rendezvoused with the spacecraft at a point about - 36,000,000 miles from the Earth._] - - [Illustration: _During the midcourse maneuver, the trajectory of - Mariner II was corrected so that the spacecraft would approach - within 21,598 miles of Venus._] - - ROLL MANEUVER ANTENNA UP - PITCH MANEUVER - MOTOR BURN - SUN REAQUISITION ANTENNA REPOSITION - EARTH REAQUISITION - -The Sun sensors then activated the gas jets and moved the spacecraft -about until the roll or long axis was pointed at the Sun. This maneuver -required only 2½ minutes after the CC&S issued the command. The solar -panel power output of 195 watts was somewhat higher than anticipated, as -were the spacecraft temperatures, which decreased and stabilized six -hours after the spacecraft oriented itself on the Sun. - -On August 29, a command from Johannesburg turned on the cruise -scientific experiments, including all the instruments except the two -radiometers. The rate of data transmission was then observed to decrease -as planned and the data conditioning system was functioning normally. - -For seven days, no attempt was made to orient the spacecraft with -respect to the Earth because the Earth sensors were too sensitive to -operate properly at such a close range. On September 3, the CC&S -initiated the Earth acquisition sequence. The gyroscopes were turned on, -the cruise scientific instruments were temporarily switched off, and a -search for the Earth began about the roll axis of the spacecraft. - -During this maneuver, the long axis of the spacecraft was held steady in -a position pointing at the Sun and the gas jets rolled the spacecraft -around this axis until the sensors, mounted in the directional antenna, -could “see” the Earth. Apparently, the Earth sensor was already viewing -the Earth because the transmitter output immediately switched from the -omni- to the directional antenna, indicating that no search was -necessary. - -However, the initial brightness reading from the Earth sensor was 38, an -intensity that might be expected if the spacecraft were locked onto the -Moon instead of the Earth. As a result, the midcourse maneuver was -delayed until verification of Earth lock was obtained. - -Mariner’s injection into the Venus trajectory yielded a predicted miss -of 233,000 miles in front of the planet, well within the normal miss -pattern expected as a result of the launch. Because the spacecraft was -designed to cross the orbit of Venus behind the planet and pass between -it and the Sun, it was necessary to correct the trajectory to an -approximate 8,000- to 40,000-mile “fly-by” so the scientific instruments -could operate within their design ranges. - -After comparison of the actual flight path with that required for a -proper near-miss, the necessary roll, pitch, and motor-burn commands -were generated by the JPL computers. When, on September 4, it had been -established that the spacecraft was indeed oriented on the Earth and not -the Moon, a set of three commands was transmitted to the spacecraft from -Goldstone, to be stored in the electronic “memory unit” until the start -command was sent. - -At 1:30 p.m., PST, the first commands were transmitted: a 9.33-degree -roll turn, a 139.83-degree pitch turn, and a motor-burn command to -produce a 69.5-mile-per-hour velocity change. - -At 2:39 p.m., a fourth command was sent to switch from the directional -antenna to the omni-antenna. Finally, a command went out instructing the -spacecraft to proceed with the now “memorized” maneuver program. - -Mariner then turned off the Earth and Sun sensors, moved the directional -antenna out of the path of the rocket exhaust stream, and executed a -9.33-degree roll turn in 51 seconds. - -Next, the pitch turn was completed in 13¼ minutes, turning the -spacecraft almost completely around so the motor nozzle would point in -the correct direction when fired. - -The spacecraft was stabilized and the roll and pitch turns controlled by -gyroscopes, which signalled the attitude control system the rate of -correction for comparison with the already computed values. - -With the solar panels no longer directly oriented on the Sun, the -battery began to share the power demand and finally carried the entire -load until the spacecraft had again been oriented on the Sun. - -At the proper time, the motor—controlled by the CC&S—ignited and burned -for 27.8 seconds, while the spacecraft’s acceleration was compared with -the predetermined values by the accelerometer. During this period, when -the gas jets could not operate properly, the spacecraft was stabilized -by movable vanes or rudders in the exhaust of the midcourse motor. - -The velocity added by the midcourse motor resulted in a decrease of the -relative speed of the spacecraft with respect to the Earth by 59 miles -per hour (from 6,748 to 6,689 miles per hour), while the speed relative -to the Sun increased by 45 miles per hour (from 60,117 to 60,162 miles -per hour). - -This apparently paradoxical condition occurred because, in order to -intercept Venus, Mariner had been launched in a direction opposite to -the Earth’s course around the Sun. The midcourse maneuver turned the -spacecraft around and slowed its travel away from the Earth while -allowing it to increase its speed around the Sun in the direction of the -Earth’s orbit. Gradually, then, the spacecraft would begin to fall in -toward the Sun while moving in the same direction as the Earth, catching -and passing the Earth on the 65th day and intersecting Venus’ orbit on -the 109th day. - -At the time of the midcourse maneuver, the spacecraft was travelling -slightly inside the Earth’s orbit by 70,000 miles, and was behind the -Earth by 1,492,500 miles. - - -THE LONG CRUISE - -After its completion of the midcourse maneuver, Mariner reoriented -itself on the Sun in 7 minutes and on the Earth in about 30 minutes. -During the midcourse maneuver, the omnidirectional antenna was used; -now, with the maneuver completed, the directional antenna was switched -back in for the duration of the mission. - -Ever since the spacecraft had left the parking orbit near the Earth and -been injected into the Venus trajectory, the Space Flight Operations -Center back in Pasadena had been the nerve center of the mission. -Telemetered data had been coming in from the DSIF stations on a 24-hour -schedule. During the cruise phase, from September 5 to December 7, a -total of 16 orbit computations were made to perfect the planet encounter -prediction. On December 7, the first noticeable Venus-caused effects on -Mariner’s trajectory were observed, causing a definite deviation of the -spacecraft’s flight path. - -On September 8, at 12:50 p.m., EST, the spacecraft lost its attitude -control, which caused the power serving the scientific instruments to -switch off and the gyroscopes to switch on automatically for -approximately three minutes, after which normal operation was resumed. -The cause was not apparent but the chances of a strike by some small -space object seemed good. - -As a result of this event, a significant difference in the apparent -brightness reading of the Earth sensor was noted. This sensor had been -causing concern for some time because its readings had decreased to -almost zero. Further decrease, if actually caused by the instrument and -not by the telemetry sensing elements, could result in loss of Earth -lock and the failure of radio contact. - -After the incident of September 8, the Earth sensor brightness reading -increased from 6 to 63, a normal indication for that day. Thereafter, -this measurement decreased in an expected manner as the spacecraft -increased its distance from the Earth. - -Mariner II was now embarked on the long cruise. On September 12, the -distance from the Earth was 2,678,960 miles and the spacecraft speed -relative to the Earth was 6,497 miles per hour. Mariner was accelerating -its speed as the Sun’s gravity began to exert a stronger pull than the -Earth’s. On October 3, Mariner was nearly 6 million miles out and moving -at 6,823 miles per hour relative to the Earth. A total of 55,600,000 -miles had been covered to that point. - -Considerable anxiety had developed at JPL when Mariner’s Earth sensor -reading had fallen off so markedly. This situation was relieved by the -unexplained return to normal on September 8, although the day-to-day -change in the brightness number was watched closely. The apparent -ability of the spacecraft to recover its former performance after the -loss of attitude control on September 8 and again on September 29 was an -encouraging sign. - -Another disturbing event occurred on October 31, when the output from -one solar panel deteriorated abruptly. The entire power load was thrown -on the other panel, which was then dangerously near its maximum rated -output. To alleviate this situation, the cruise scientific instruments -were turned off. A week later, the malfunctioning panel returned to -normal operation and the science instruments were again turned on. -Although the trouble had cleared temporarily, it developed again on -November 15 and never again corrected itself. The diagnosis was a -partial short circuit between one string of solar cells and the panel -frame, but by now the spacecraft was close enough to the Sun so that one -panel supplied enough power. - -By October 24, the spacecraft was 10,030,000 miles from the Earth and -was moving at 10,547 miles per hour relative to the Earth. The distance -from Venus was now 21,266,000 miles. - -October 30 was the 65th day of the mission and at 5 a.m., PST, Mariner -overtook and passed the Earth at a distance of 11,500,000 miles. Since -the spacecraft’s direction of travel had, in effect, been reversed by -the midcourse maneuver, it had been gaining on the Earth in the -direction of its orbit, although constantly falling away from the Earth -in the direction of the Sun. - -The point of equal distance between the Earth and Venus was passed on -November 6, when Mariner was 13,900,000 miles from both planets and -travelling at 13,843 miles per hour relative to the Earth. As November -wore on, hope for a successful mission began to mount. Using tracking -data rather than assumptions of standard midcourse performance, the -Venus miss distance had now been revised to about 21,000 miles and -encounter was predicted for December 14. But the DSIF tracking crews, -the space flight and computer operators, and the management staff could -not yet relax. The elation following the successful trajectory -correction maneuver on September 4 had given way alternately to -discouragement and guarded optimism. - -Four telemetry measurements were lost on December 9 and never returned -to normal. They measured the angle of the antenna hinge, the fuel tank -pressure, and the nitrogen pressure in the midcourse and attitude -control systems. A blown fuse, designed to protect the data encoder from -short circuits in the sensors, was suspected. However, these channels -could not affect spacecraft operation and Mariner continued to perform -normally. - -The rising temperatures recorded on the spacecraft were more serious. -Only the solar panels were displaying expected temperature readings; -some of the others were as much as 75 degrees above the values predicted -for Venus encounter. The heat increase became more rapid after November -20. By December 12, six of the temperature sensors had reached their -upper limits. It was feared that the failure point of the equipment -might be exceeded. - -The CC&S performed without incident until just before encounter, when, -for the first time, it failed to yield certain pulses. JPL engineers -were worried about the starting of the encounter sequence, due the next -day, although they knew that Earth-based radio could send these -commands, if necessary. - -On December 12, with the climax of the mission near, the spacecraft was -34,218,000 miles from the Earth, with a speed away from the Earth of -35,790 miles per hour, a Sun-relative speed of 83,900 miles per hour. - -Only 635,525 miles from Venus at this point, Mariner II was closing fast -on the cloud-shrouded planet. But it was a hot spacecraft that was -carrying its load of inquisitive instruments to the historic encounter. - - -ENCOUNTER AND BEYOND - -On its 109th day of travel, Mariner had approached Venus in a precarious -condition. Seven of the over-heated temperature sensors had reached -their upper telemetry limits. The Earth-sensor brightness reading stood -at 3 (0 was the nominal threshold) and was dropping. Some 149 watts of -power were being consumed out of the 165 watts still available from the -crippled solar panels. - -At JPL’s Space Flight Operations Center, there was reason to believe -that the ailing CC&S might not command the spacecraft into its encounter -sequence at the proper time. Twelve hours before encounter, these fears -were verified. - -Quickly, the emergency Earth-originated command was prepared for -transmission. At 5:35 a.m., PST, a radio signal went out from -Goldstone’s Echo Station. Thirty-six million miles away, Mariner II -responded to the tiny pulse of energy from the Earth and began its -encounter sequence. - -After Mariner had “acknowledged” receipt of the command from the Earth, -the spacecraft switched into the encounter sequence as engineering data -were turned off and the radiometers began their scanning motion, taking -up-and-down readings across the face of the planet. As throughout the -long cruise, the four experiments monitoring the magnetic fields, cosmic -dust, charged particles, and solar plasma experiments continued to -operate. - - [Illustration: _Mariner II approached Venus from the dark side, - crossed between the planet and the Sun while making three radiometer - scans of the disk._] - -As Mariner approached Venus on its night side, it was travelling about -88,400 miles per hour with respect to the Sun. At the point of closest -approach, at 11:59.28 a.m., PST, the distance from the planet was 21,598 -miles. - -During encounter with Venus, three scans were made: one on the dark -side, one across the terminator dividing dark and sunlit sides, and one -on the sunlit side. Although the scan went slightly beyond the edge of -the planet, the operation proceeded smoothly and good data were received -on the Earth. - -With encounter completed, the cruise condition was reestablished by -radio command from the Earth and the spacecraft returned to transmitting -engineering data, together with the continuing readings of the four -cruise scientific experiments. - -After approaching closer to a planet and making more meaningful -scientific measurements than any man-made space probe, Mariner II -continued on into an orbit around the Sun. - -December 27, 13 days after Venus encounter, marked the perihelion, or -point of Mariner’s closest approach to the Sun: 65,505,935 miles. The -Sun-related speed was 89,442 miles per hour. As Mariner began to pull -away from the Sun in the following months, its Sun-referenced speed -would decrease. - -Data were still being received during these final days and the Earth and -Sun lock were still being maintained. Although the antenna hinge angle -was no longer being automatically readjusted by the spacecraft, commands -were sent from the Earth in an attempt to keep the antenna pointed at -the Earth, even if the Earth sensor were no longer operating properly. - -At 2 a.m., EST, January 3, 1963, 20 days after passing Venus, Mariner -finished transmitting 30 minutes of telemetry data to Johannesburg and -the station shut down its operation. When Woomera’s DSIF 4 later made a -normal search for the spacecraft signal, it could not be found. -Goldstone also searched in vain for the spacecraft transmissions, but -apparently Mariner’s voice had at last died, although the spacecraft -would go into an eternal orbit around the Sun. - -It was estimated that Mariner’s aphelion (farthest point out) in its -orbit around the Sun would occur on June 18, 1963, at a distance of -113,813,087 miles. Maximum distance from the Earth would be 98,063,599 -miles on March 30, 1963; closest approach to the Earth: 25,765,717 miles -on September 27, 1963. - - -THE RECORD OF MARINER - -The performance record of Mariner II exceeded that of any spacecraft -previously launched from Earth: - - -—It performed the first and most distant trajectory-correcting maneuver - in deep space, firing a rocket motor at the greatest distance from the - Earth: 1,492,000 miles (September 4, 1962). - -—The spacecraft transmitted continuously for four months, sending back - to the Earth some 90 million bits of information while using only 3 - watts of transmitted power. - -—Useful telemetry measurements were made at another record distance from - the Earth: 53.9 million miles (January 3, 1963). - -—Mariner II was the first spacecraft to operate in the immediate - vicinity of another planet and return useful scientific information to - the Earth: approximately 21,598 miles from Venus (December 14, 1962). - -—Measurements were made closest to the Sun: 65.3 million miles away - (December 27, 1962). - -—Mariner’s communication system operated for the longest continuous - period in interplanetary space: 129 days (August 27, 1962, to January - 3, 1963). - -—Mariner achieved the longest continuous operation of a spacecraft - attitude-stabilization system in space, and at a greater distance from - the Earth than any previous spacecraft: 129 days (August 27, 1962, to - January 3, 1963), at 53.9 million miles from the Earth. - - - - - CHAPTER 6 - THE TRACKING NETWORK - - -Thirty-six million miles separated the Earth from Venus at encounter. -Communicating with Mariner II and tracking it out to this distance, and -beyond, represented a tremendous extension of man’s ability to probe -interplanetary space. - -The problem involved: - - 1. The establishment of the spacecraft’s velocity and position - relative to the Earth, Venus, and the Sun with high precision. - 2. The transmission of commands to activate spacecraft maneuvers. - 3. The reception of readable spacecraft engineering and scientific - data from the far-ranging Mariner. - -The tracking network had to contend with many radio noise sources: the -noise from the solar system and from extragalactic origins; noise -originating from the Earth and its atmosphere; and the inherent -interference originating in the receiving equipment. These problems were -solved by using advanced high-gain antennas and ultra-stable, extremely -sensitive receiving equipment. - - -DEEP SPACE INSTRUMENTATION FACILITY - -The National Aeronautics and Space Administration has constructed a -network of deep-space tracking stations for lunar and planetary -exploration missions. In order to provide continuous, 24-hour coverage, -three stations were built, approximately 120 degrees of longitude apart, -around the world: at Goldstone in the California desert, near -Johannesburg in South Africa, and at Woomera in the south-central -Australian desert. - - [Illustration: _The three tracking stations of the Deep Space - Instrumentation Facility are located around the world so as to - provide continuous flight coverage._] - -These stations are the basic elements of the Deep Space Instrumentation -Facility (DSIF). In addition, a mobile tracking station installed in -vans is used near the point of injection of a spacecraft into an -Earth-escape trajectory to assist the permanent stations in finding the -spacecraft and to acquire tracking data. The control point for the DSIF -net is located at JPL in Pasadena, California (see Table 1). - -The Jet Propulsion Laboratory has the responsibility for the technical -direction of the entire DSIF net and operates the Goldstone facilities -with assistance from the Bendix Corporation as a subcontractor. The -overseas stations are staffed and operated by agencies of the Republic -of South Africa and the Commonwealth of Australia. - -The DSIF net tracks the position and velocity of U.S. deep-space probes, -issues commands to direct the spacecraft in flight, receives engineering -and scientific data from the probes, and automatically relays the data -to JPL in Pasadena, where it is processed by computers and interpreted. -(In the tracking operation, a signal is transmitted to the spacecraft, -where it is received and processed in a transponder, which then sends -the signal back to the Earth. The change in frequency, known as the -doppler effect, involved in this operation enables engineers to -determine the velocity at which the spacecraft is moving.) - - - _Table 1. Deep Space Instrumentation Facility Stations_ - - _Station_ _Location_ _Equipment_ _Functions_ - - DSIF 1 (Mobile Near point of 10-ft antenna Fast tracking - Tracking injection of 25-w, 890-mc for acquisition - Station) spacecraft into transmitter of spacecraft - Earth-escape - trajectory - Goldstone: California - Pioneer Site 85-ft Reception of - (DSIF 2) polar-mount telemetry - antenna; Tracking - Cassegrain spacecraft - feed; maser and - parametric - amplifier - Echo Site 85-ft Transmission of - (DSIF 3) polar-mount commands - antenna; Tracking - parametric spacecraft - amplifier Stand-by - 10-kw, 890-mc reception - transmitter - Venus Site 85-ft Advanced radar - radar-type astronomy - antenna Communications - research - DSIF 4 Woomera, 85-ft Reception of - Australia polar-mount telemetry - antenna; Tracking - parametric spacecraft - amplifier - DSIF 5 Johannesburg, 85-ft Reception of - South Africa polar-mount telemetry - antenna; Tracking - parametric spacecraft - amplifier Transmission of - 10-kw, 890-mc commands - transmitter - -The stations are equipped with receiving and tracking instruments so -sensitive that engineers estimate that they can detect radio-frequency -energy equivalent to that radiated by a 1-watt light bulb at a distance -of approximately 75 to 80 million miles. Such energy received at the -antenna would measure about 0.00000000000000000002 watt (2 × 10⁻²⁰). - -The amount of power received at the antenna during Mariner’s encounter -with Venus has been calculated at about 0.000000000000000001 of a watt -(1 × 10⁻¹⁸). If a 100 percent efficient storage battery were charged -with this amount of energy for some 30 billion years, the battery would -then have stored enough energy to light an ordinary 1-watt flashlight -bulb for about 1 second only. - -Furthermore, Goldstone engineers estimate that, if Mariner II had -continued to function in all its systems and to point its directional -antenna at the Earth, useful telemetry data could have been obtained by -the DSIF stations out to about 150 to 200 million miles, and tracking -data could have been secured from as far as 300 to 400 million miles. - -Construction of the DSIF net was begun in 1958. The Goldstone station -was ready for the Pioneer III mission in December of that year. In -March, 1959, Pioneer IV was successfully tracked beyond the Moon. Later -in 1959, Pioneer V was tracked out to over 3 million miles. - -Goldstone participated in the 1960 Project Echo communication satellite -experiments and the entire net was used in the Ranger lunar missions of -1961-1962. The Goldstone station performed Venus radar experiments in -1961 and 1962 to determine the astronomical unit more precisely and to -study the rotation rate and surface characteristics of the planet. - -Following the launch of Mariner II on August 27, 1962, the full DSIF net -provided 24-hour-per-day tracking coverage throughout the mission except -for a few days during the cruise phase. The net remained on the -full-coverage schedule through the period of Venus encounter on December -14. - - -THE GOLDSTONE COMPLEX - -The tracking antennas clustered in a 7-mile radius near Goldstone Dry -Lake, California, are the central complex of the DSIF net. Three -tracking sites are included in the Goldstone Station: Pioneer Site (DSIF -2), Echo Site (DSIF 3), and Venus Site. The Venus Site is used for -advanced radar astronomy, communication research experiments, and radio -development; it took no direct part in the Mariner spacecraft tracking -operations, but was used for the Venus radar experiments. - -Pioneer Site has an 85-foot-diameter parabolic reflector antenna and the -necessary radio tracking, receiving, and data recording equipment. The -antenna can be pointed to within better than 0.02 of a degree. The -antenna has one (hour-angle) axis parallel to the polar axis of the -Earth, and the other (declination) axis perpendicular to the polar axis -and parallel to the equatorial plane of the Earth. This “polar-mount” -feature permits tracking on only one axis without moving the other. - -The antenna weighs about 240 tons but can be rotated easily at a maximum -rate of 1 degree per second. The minimum tracking rate or antenna swing -(0.250686486 degree per minute) is equal to the rotation rate of the -Earth. Two drive motors working simultaneously but at different speeds -provide an antibacklash safety factor. The antenna can operate safely in -high winds. - -The Pioneer antenna has a type of feed system (Cassegrain) that is -essentially similar to that used in many large reflector telescopes. A -convex cone is mounted at the center of the main dish. A received signal -is gathered by the main dish and the cone, reflected to a subreflector -on a quadripod, where the energy is concentrated in a narrow beam and -reflected back to the feed collector point on the main dish. The -Cassegrain feed system lowers the noise picked up by the antenna by -reducing interference from the back of the antenna, and permits more -convenient location of components. - -The receiving system at Pioneer Site is also equipped with a low-noise, -extremely sensitive installation combining a parametric amplifier and a -maser. The parametric amplifier is a device that is “pumped” or excited -by microwave energy in such a way that, when an incoming signal is at -its maximum, the effect is such that the “pumped-in” energy augments the -original strength of the incoming signal. At the same time, the -parametric amplifier reduces the receiving system’s own electronic noise -to such a point that the spacecraft can be tracked twice as far as -before. - -The maser uses a synthetic ruby mixed with chromium and is maintained at -the temperature of liquid helium—about 4.7 degrees K or -450 degrees F -(just above absolute zero)—and when “pumped” with a microwave field, the -molecular energy levels of the maser material are redistributed so as to -again improve the signal amplification while lowering the system noise. -The maser doubles the tracking capability of the system with a -parametric amplifier, and quadruples the capability of the receiver -alone. - -The antenna output at Pioneer is a wide-band telemetering channel. In -addition, the antenna can be aimed automatically, using its own “error -signals.” At both the Pioneer and Echo sites at Goldstone, however, the -antenna is pointed by a punched tape prepared by a special-purpose -computer at JPL and transmitted to Goldstone by teletype. - -Pioneer Site has a highly sensitive receiver designed to receive a -continuous wave signal in a narrow frequency band in the 960-megacycle -range. The site has equipment for recording tracking data for use by -computers in determining accurate spacecraft position and velocity. - -The instrumentation equipment also includes electronic signal processing -devices, magnetic-tape recorders, oscillographs, and other supplementary -receiving equipment. The telemetered data can be decommutated (recovered -from a signal shared by several measurements on a time basis), encoded, -and transmitted by teletype in real time (as received from the -spacecraft) to JPL. - -Echo Site is the primary installation in the Goldstone complex and has -antenna and instrumentation facilities identical to those at Pioneer, -except that there is no maser amplifier and a simpler feed system is -used instead of the Cassegrain. However, Echo was used as a transmitting -facility and only as a stand-by receiving station during the Mariner -mission. - -Echo has a 10-kilowatt, 890-megacycle transmitter which was utilized for -sending commands to the Mariner spacecraft. In addition, the site has an -“atomic clock” frequency standard, based on the atomic vibrations of -rhubidium, which permits high-precision measurements of the radial -velocity of the spacecraft. A unit in the Echo system provides for -“readback” and “confirmation” by the spacecraft of commands transmitted -to it. In a sense, the spacecraft acknowledges receipt of the commands -before executing them. - -Walter E. Larkin manages the Goldstone Station for JPL. - - -THE WOOMERA STATION - -The Woomera, Australia, Station (DSIF 4), managed by William Mettyear -for the Australian Department of Supply, has essentially the same -antenna and tracking capabilities as Goldstone Echo Site, but it has no -provisions for commanding the spacecraft. A small transmitter is used -for tracking purposes only. The station is staffed and operated by the -Australian Department of Supply. - - [Illustration: _The Mobile Tracking Station (DSIF 1) follows the - fast-moving spacecraft during its first low-altitude pass over South - Africa._] - - [Illustration: _Station 5 of the DSIF is located near Johannesburg - in South Africa._] - - [Illustration: _DSIF 4, at Woomera, dominates the landscape in - Australia’s “outback.”_] - -Woomera, like Johannesburg, is capable of receiving tracking (position -and velocity) data and telemetered information for real-time -transmission by radio teletype to JPL. - - -THE JOHANNESBURG STATION - -DSIF 5 is located just outside Johannesburg in the Republic of South -Africa. This station is staffed by the National Institute of -Telecommunications Research (NITR) of the South African Council for -Scientific and Industrial Research and managed by Douglas Hogg. - -The antenna and receiving equipment are identical to the Goldstone Echo -Site installation except for minor details. The station has both -transmitting and receiving capability and can send commands to the -spacecraft. Recorded tracking and telemetered data are transmitted in -real time to JPL by radio teletype. - - -MOBILE TRACKING STATION - -The Mobile Tracking Station (DSIF 1) is a movable installation designed -for emplacement near the point of injection of a space probe to assist -the permanent stations in early acquisition of the spacecraft. This -station is necessary because at this point the spacecraft is relatively -low in altitude and consequently appears to move very fast across the -sky. The Mobile Tracking Station has a fast-tracking antenna for use -under these conditions. DSIF 1 was located near the South African -station for Mariner II. It has a 10-foot parabolic antenna capable of -tracking at a 10-degree-per-second rate. A 25-watt, 890-megacycle -transmitter is used for obtaining tracking information. A diplexer -permits simultaneous transmission and reception on the same antenna -without interference. - -The equipment is installed in mobile vans so that the station can be -operated in remote areas. The antenna is enclosed in a plastic dome and -is mounted on a modified radar pedestal. The radome is inflatable with -air and protects the antenna from wind and weather conditions. - -These stations of the DSIF tracked Mariner II in flight and sent -commands to the spacecraft for the execution of maneuvers. The telemetry -data received from the spacecraft during the 129 days of its mission -were recorded and transmitted to JPL, where the information was -processed and reduced by the computers of the space flight operations -complex. - - - - - CHAPTER 7 - THIRTEEN MILLION WORDS - - -The task of receiving, relaying, processing, and interpreting the data -coming in simultaneously on a twenty-four-hour basis for several months -from the several scientific and many engineering sources of the Mariner -spacecraft was of truly monumental proportions. - -This activity involved five DSIF tracking stations scattered around the -world, a communication network, two computing stations and auxiliary -facilities, and some 400 personnel over a four-month period. - -Although the Mariner scientific information could be stored and -subsequently processed at a later (non-real) time, it was necessary to -make tracking and position data available almost as soon as it was -received (in real time) so that the midcourse maneuver might be computed -and transmitted to the spacecraft, and to further perfect the predicted -trajectory and arrival time at Venus. - -The engineering performance of the many spacecraft subsystems was also -of vital concern. Inaccurate operation in any of several areas could -endanger the success of the entire mission. The performance of the -attitude control system, the Earth and Sun sensors, the power system, -and communications were all of critical importance. Corrective action -was possible in certain subsystems where trouble could be predicted from -the data or where limited breakdown had occurred. - -To integrate all the varied activities necessary to accomplish the -mission objectives, an organization was formed within JPL to coordinate -the DSIF, the communication network, the work of engineering and -scientific advisory panels, and the computer facilities required to -evaluate the data. - -This organization was known as the Space Flight Operations Complex. For -operational purposes only, it included the Space Flight Operations -Center, a Communication Center, and a Central Computing Facility (CCF). -The DSIF was responsive to the requirements of the organization, but was -not an integral part of it. - -A space flight operations director was responsible for integrating these -many functions into a world-wide Mariner space-flight organization. It -was an exhausting 109-day task, one that would severely tax all the -resources of JPL in terms of know-how, qualified personnel, time, and -equipment before Mariner completed its encounter with Venus. - - -COMMUNICATION CONTROL - -The Communication Center at JPL in Pasadena was one of the most active -areas during the many days and nights of the Mariner II mission. All of -the teletype and radio lines from the Cape, South Africa, Australia, and -Goldstone terminated in this Center. A high-speed data line bypassed the -Communication Center, linking Goldstone directly with the Central -Computing Facility for quick, real-time computer processing of vital -flight information. - -From the Communication Center, the teletype data and voice circuits were -connected to the several areas within JPL where the mission-control -activities were centered, and where the data output was being studied. - -The Communication Center was equipped with teletype paper-page printers -and paper-tape hole reperforators, which received and transmitted -data-word and number groups. The teletype lines terminating at the -Center included circuits from Goldstone, South Africa, Australia, and -Cape Canaveral. - -There were three lines to Goldstone for full-time, one-way data -transmission. Duplex (simultaneous two-way) transmission was available -to Woomera and South Africa on a full-time basis. In each case, a -secondary circuit was provided to the overseas sites for use during -critical periods and in case the primary radio-teletype circuits had -transmission difficulties. These secondary circuits used different radio -transmission paths in order to reduce the chance of complete loss of -contact for any extended period of time. - - [Illustration: _Radio signals from Mariner are received on 85-ft. - antenna._] - - [Illustration: _The highly sensitive receiver (shown under test) is - located in the control room of the station._] - - [Illustration: _In Goldstone control room, DSIF personnel await - confirmation that spacecraft has begun to scan the planet Venus._] - - [Illustration: _From DSIF stations, the data are teletyped in coded - format to Pasadena._] - -Z ZSQSGSGKGKXRGOQOS DNQ XZARZXAVAQQVA XXDRDZ -QSGIGKGKXRGOQOX DXQ XZAIZXAVQQKDZ XXDRDDDRZ -DXQ XZAIZAZVAQQZDZXXDLKKDRA Z DSQSGIGGGQXRDN -G XXDRZSDRA Z DSQSGIGGGQXRGLZOX DXQ XZAIZAZV -QSGIGGGQXRGLZOX DXQ XZAIZGAVAQQSXZXXDRDZDRA -DXQ XQAIZGAVQQKVA XXDRDZDRANGDSSQSGIGGGQXRDI -Z XXDRDDDRZLQ ZSQSGIGGGGXRGVZOA DNQ XZARZGAV -QSGIGGGGXRGVQOA DNQ XZARZGAVQKZZAZXXDRZDDRA -DNQ XZARZAZVAKDDGZXXDRDADIZLA DSQSGIGGGGXRGZ -SZXXDRDDDRXOS DSQSQIGGGGXRDDZOA DNQ XZARZXAV -QSGSGGGGXRDSQOG DXQ XZARZXAVAKDZDZXXDRDLDRA -DXQ XZARZXAZZKZZDZXXDLKADRA Z DSQSGIGGGGXRGX -GZXXDRZXDRZ Z DSQSAQGGGGXRDAZOG DXQ XZAIZAZV -DRDXDRA Z DSQSGIGGGGXRDGSOG DXQ XZAIZAZVQKZS -OGGGXRDGAOG DXQ XZAIZAZVQKZVA XXDRDZDRANGDSS -XZAIZXAZZKZZD XXDRDLZDZHA DSQSGIGGGGXRDQAOQ -DLKADRKHQ ZSQSGIGGGGXRDKZOQ DXQ XZAVZAAVQKZZ -GGGGXRS ZOQ DXQ XZAIZAZVQKZDG XXDRDSDIZ A ZS -XZAIZAZVQQKSX XXDRDDDRZNS ZSQSGIGGGGXRSOAOQ -DRDZDRANGDSSQSAQGGGGXRSOAOK DNQ XZAVZAAVQQKZ -GGGGXRSNZOK DNQ XZAIZAZZSQQZSZXXDLKADRA Z DS -XZAIZGAVQQKZG XXDRZXDRZ Z DSQSAQGGGGXRSLAOK -DRDSDRZ Z DSQSAQGGGGXRSLAOK DNQ XZAIZAZZZQKS -GGGGXRSLAOK DNQ XZAIZAZZZQKVA XXDRDZDRANGDSS -XRSIZHZ DXQ XZAIZAZZZQKQQZXXDRDNDRZNQ DSQSGS -ZXAZSQQZXZXXDLKQDRSQS ZSQSGIGGGQXRSVAHZ DXQ - - [Illustration: _Messages are received and routed at the JPL - Communications Center._] - - [Illustration: _Data are routed to the digital computer at JPL._] - - [Illustration: _Printout data are made available to experimenters._] - - [Illustration: _Spacecraft status is posted in Operations Center._] - -The Mobile Tracking Station in South Africa used the Johannesburg -communication facilities. - -Two one-way circuits for testing and control purposes were open to Cape -Canaveral from a month before until after the spacecraft was launched. -Lines from the Communication Center to the Space Flight Operations -Center at JPL terminated in page printers and reperforators in several -locations. - -Voice circuits connected all of the stations with Operations Center -through the Communication Center. Long-distance radio telephone calls -were placed to South Africa to establish contact before the launch -sequence was started. Woomera used the Project Mercury voice circuits to -the United States during launch and for three days after. - - -THE OPERATIONS CENTER - -The actual nerve center of the Mariner operation was the Space Flight -Operations Center (SFOC) at Pasadena. Here, technical and scientific -advisory panels reported to the Project Manager and the Mariner Test -Director on the performance of the spacecraft in flight, analyzed -trajectories, calculated the commands for the midcourse trajectory -correction, and studied the scientific aspects of the mission. - -These panels were a Spacecraft Data Analysis Team, a Scientific Data -Group, an Orbit Determination Group, a Tracking Data Analysis Group, and -a Midcourse Command Group. - -The Spacecraft Data Analysis Team analyzed the engineering data -transmitted from the spacecraft to evaluate the performance of the -subsystems in flight. The Team was composed of one or more of the -engineers responsible for each of the spacecraft subsystems, and a -chairman. - -The Science Data Group was composed of the project scientist and certain -other scientists associated with the experiments on board the -spacecraft. This Group evaluated the data from the scientific -experiments while Mariner was in flight and advised the Test Director on -the scientific status of the mission. - -The Science Data Group was on continuous duty until 48 hours after -launch, and at other times during the mission. During encounter with -Venus, the Group was also in contact with the scientific experimenters -from other participating organizations who were working with JPL. - - [Illustration: _Closed circuit television monitors are used for - instant surveillance of the internal activities of the Operations - Center._] - -A Tracking Data Analysis Group analyzed the tracking data to be used in -orbit determination. They also assessed the performance of the DSIF -facilities and equipment used to obtain the data. - -The Orbit Determination Group used the tracking data to produce -estimates of the actual spacecraft trajectory, and to compute the -spacecraft path with respect to the Earth, Venus, and the Sun. These -calculations were made once each day before the midcourse maneuver, once -a week during the cruise phase, and daily during and immediately after -the planet encounter. - -The Operations Center was equipped with lighted boards on which the -progress of the mission was displayed. This information included -trajectory data, spacecraft performance, temperature and pressure -readings, and other data telemetered from the spacecraft subsystems. - -Closed-circuit television was used for coordinating the activities of -the SFOC. Operating personnel could use television monitors in four -consoles which were linked to six fixed cameras viewing teletype page -printers. The entire Operations Room could be kept under surveillance by -the Project Manager, the Test Director, or the DSIF Operations Manager, -using cameras controlled in “pan,” “tilt,” and “zoom.” - - -CENTRAL COMPUTING FACILITY - -During the Mariner II mission, the JPL Central Computing Facility (CCF) -processed approximately 13.1 million data words, or over 90 million -binary bits of computer data. (Binary bit = a discrete unit of -information intelligible to a digital computer. One data word = 7 binary -bits.) - -In the four-month operation, about 100,000 tracking and telemetering -data cards were received and processed, yielding over 1.2 million -computer pages of tabulated, processed, and analyzed data for evaluation -by the engineers and scientists. Approximately 1,000 miles of magnetic -tape were used in the 1,056 rolls recorded by the DSIF. - -The Central Computing Facility processed and reduced tracking and -telemetry data from the spacecraft, as recorded and relayed by the -stations of the DSIF. The tracking information was the basis for orbital -calculations and command decisions. After delivery of telemetry data on -magnetic tapes by the DSIF, the CCF stored the data for later reduction -and analysis. Where telemetry data were being processed in real or -near-real time, certain critical engineering and scientific functions -were programmed to print-out an “alarm” reading when selected -measurements in the data were outside specified limits. - -The CCF consists of three stations at JPL: Station C, the primary -computing facility; Station D, the secondary installation; and the -Telemetry Processing Station (TPS). - -Station C was the principal installation for processing both tracking -and telemetry data received from the DSIF tracking stations, both in -real and non-real time. The Station was equipped with a high-speed, -general-purpose digital computer with a 32,168-word memory and two -input-output channels, each able to handle 6 tape units. The associated -card-handling equipment was also available. - -Tape translators or converters were provided for converting teletype -data and other digital information into magnetic tape format for -computer input. The teletype-to-tape unit operated at a rate of 300 -characters per second. - -A smaller computer acted as a satellite of the larger unit, performing -bookkeeping and such related functions as card punching, card reading, -and listing. - -A high-speed unit microfilmed magnetic-tape printout was received from -the large computer. It provided “quick-look” copy within 30 minutes of -processing the raw data. Various paper-tape-to-card and -card-to-paper-tape converters were used to eliminate human error in -converting teletype data tape to computer cards. - -Station C also utilized another computer as a real-time monitor and to -prepare a magnetic tape file of all telemetered measurements for input -to the large computer. - -Station D was the secondary or backup computational facility, primarily -intended for use in case of equipment failure in Station C. During -certain critical phases of the Mariner mission—launch, orbit -determination, midcourse maneuver—this facility paralleled the -operations in Station C. - -Station D is equipped with three computers and various card-to-tape -converters and teletype equipment. - -The Telemetry Processing Station received and processed all demodulated -data (that recovered from the radio carrier) on magnetic tapes recorded -at the DSIF stations. The TPS output was digital magnetic tapes suitable -for computer entry. - -The TPS equipment included FM discriminators, a code translator, a -device for converting data from analog to digital form, and -magnetic-tape recorders. Basically, the equipment accepted the digital -outputs from the tape units, the analog-to-digital converter, and the -code translator and put them in digital tape format for the computer -input. - -As the launch operation started on August 27, the powered-flight portion -of the space trajectories program was run at launch minus 5 minutes (L -minus 5) and was repeated several times because of holds at AMR. The -orbit determination program was run at lift-off to calculate the first -orbit predictions used for aiding the DSIF in finding the spacecraft in -flight. - -During the 12 hours following launch, both C and D Stations performed -parallel computations on tracking data. Station D discontinued space -flight operations at L plus 12 hours and resumed at the beginning of the -midcourse maneuver phase. - -Tracking data processing and midcourse maneuver studies were conducted -daily until the midcourse maneuver was performed at L plus eight days. -For the following 97 days, tracking data were processed once each week -for orbit determination. Starting three days before the encounter, -tracking data were processed daily until the beginning of the encounter -phase. - -Tracking data processing was conducted in near-real time throughout -encounter day, and daily for two days thereafter. For these three days, -tracking data were handled in Station D in order to permit exclusive use -of Station C for telemetry data processing and analysis. After this -three-day period, including the encounter, Station C processed the -tracking data every sixth day until the mission terminated on L plus 129 -days. - -Telemetry data were processed in a different manner. Following the -launch, DSIF Station 5 at South Africa received the telemetry signal -first, demodulated it, and put it in the proper format for teletype -transmission to JPL. The other DSIF stations followed in sequence as the -spacecraft was heard in other parts of the world. For two days after -launch, the computers processed telemetry data as required by the -Spacecraft Data Analysis Team. - -During those periods when the large computer was processing tracking -data, a secondary unit supplied quick-look data in near-real time. When -Goldstone was listening to the spacecraft, quick-look data were -processed in real time, using the high-speed data line direct to the -Central Computing Facility. - -For the 106 days that Mariner was actually in Mode II (cruise), the -telemetry data were processed twenty-four hours a day, seven days a -week. Data were presented to the engineering and science analysis teams -in quick-look format every three hours, except for short maintenance -interruptions, one computer failure, and a major modification requiring -three days, when a back-up data process mode of operation was used. The -large computer performed full processing and analysis of engineering and -science data seven days a week from launch until the Venus encounter. - -On encounter day, the secondary Station C computer processed telemetry -data from the high-speed Goldstone line. Data on magnetic tapes produced -by the computer were processed and analyzed by the large unit in -near-real time every 30 minutes. The computer processing and delivery -time during this operation varied from 4½ to 7 minutes. - - - - - CHAPTER 8 - THE SCIENTIFIC EXPERIMENTS - - -After a year of concentrated effort, in which the resources of NASA, the -Jet Propulsion Laboratory, and American science and industry had been -marshalled, Mariner II had probed secrets of the solar system some -billions of years old. - -Scientists and engineers had studied the miles of data processed in -California from the tapes recorded at the five DSIF tracking stations -around the world. Two and a half months of careful analysis and -evaluation yielded a revised estimate of Venus and of the phenomena of -space. As a result, the dynamics of the solar system were revealed in -better perspective and the shrouded planet stood partially unmasked. -When the Mariner data were correlated with the data gathered by JPL -radar experiments at Goldstone in 1961 and 1962, the relationships -between the Earth, Venus, and the Sun became far clearer than ever -before. - -Two experiments were carried on the spacecraft for a close-up -investigation of Venus’ atmosphere and temperature characteristics—a -microwave radiometer and an infrared radiometer. They were designed to -operate during the approximate 35-minute encounter period and at a -distance varying from about 10,200 miles to 49,200 miles from the center -of the planet.[2] - - [Illustration: _Cosmic dust detector._] - - [Illustration: _Solar plasma spectrometer._] - - COLLECTOR CUP - PROGRAMMER - ELECTROMETER - DEFLECTION PLATES - - [Illustration: _Magnetometer._] - - [Illustration: _High-energy particle detector._] - - COLLECTOR - SHIELD CAN - QUARTZ FIBER - - [Illustration: _Microwave and infrared radiometers._] - - REFERENCE HORNS - MICROWAVE RADIOMETER - INFRARED RADIOMETER - - - _Table 2. Mariner Experiments_ - - _Experiment_ _Description_ _Experimenters_ - - Microwave radiometer Determine the Dr. A. H. Barrett, - temperature of the Massachusetts - planet surface and Institute of - details concerning Technology; D. E. - its atmosphere Jones, JPL; Dr. J. - Copeland, Army - Ordnance Missile - Command and - Ewen-Knight Corp.; - Dr. A. E. Lilley, - Harvard College - Observatory - Infrared radiometer Determine the Dr. L. D. Kaplan, JPL - structure of the and University of - cloud layer and Nevada; Dr. G. - temperature Neugebauer, JPL; Dr. - distributions at C. Sagan, University - cloud altitudes of California, - Berkeley, and Harvard - College Observatory - Magnetometer Measure planetary and P. J. Coleman, NASA; - interplanetary Dr. L. Davis, - magnetic fields Caltech; Dr. E. J. - Smith, JPL; Dr. C. P. - Sonett, NASA - Ion chamber and Measure high-energy Dr. H. R. Anderson, - matched cosmic radiation JPL; Dr. H. V. Neher, - Geiger-Mueller tubes Caltech - Anton special-purpose Measure lower Dr. J. Van Allen and - tube radiation (especially L. Frank, State - near Venus) University of Iowa - Cosmic dust detector Measure the flux of W. M. Alexander, - cosmic dust Goddard Space Flight - Center, NASA - Solar plasma Measure the intensity M. Neugebauer and Dr. - spectrometer of low-energy C. W. Snyder, JPL - positively charged - particles from the Sun - -Four experiments for investigation of interplanetary space and the -regions near Venus employed: a magnetometer; high-energy charged -particle detectors, including an ionization chamber and Geiger-Mueller -radiation counters; a cosmic dust detector; and a solar plasma detector. - -These six scientific experiments represented the cooperative efforts of -scientists at nine institutions: The Army Ordnance Missile Command, the -Ewen-Knight Corp., the California Institute of Technology, the Goddard -Space Flight Center of NASA, Harvard College Observatory, the Jet -Propulsion Laboratory, the Massachusetts Institute of Technology, the -State Universities of Iowa and Nevada, and the University of California -at Berkeley. Table 2 lists the experiments, the experimenters, and their -affiliations. - -At the Jet Propulsion Laboratory, the integration of the scientific -experiments and the generation of a number of them were carried out -under the direction of Dr. Manfred Eimer. R. C. Wyckoff was the project -scientist and J. S. Martin was responsible for the engineering of the -scientific experiments. - - -DATA CONDITIONING SYSTEM - -Mariner’s scientific experiments were controlled and their outputs -processed by a data conditioning system which gathered the information -from the instruments and prepared it for transmission to the Earth by -telemetry. In this function, the data system acted as a buffer between -the science systems and the spacecraft data encoder. - -The pulse output of certain of the science instruments was counted and -the voltage amplitude representations of other instruments were -converted from analog form to a binary digital equivalent of the -information signals. The data conditioning system also included circuits -to permit time-sharing of the telemetry channels with the spacecraft -engineering data, generation of periodic calibration signals for the -radiometer and magnetometer, and control of the direction and speed of -the radiometer scanning cycle. - -During Mariner’s cruise mode, the data conditioning system was used for -processing both engineering and science data. If the spacecraft lost -lock on the Sun or the Earth during the cruise mode, no scientific data -would be telemetered during the reorientation period. Engineering data -were sampled and transmitted for about 17 seconds during every 37-second -interval. The planetary encounter mode involved only science and no -engineering data transmission. In this mode, the science data were -sampled during 20-second intervals. - - -COSMIC DUST DETECTOR - -The cosmic dust detector on Mariner II was designed to measure the flux -density, direction, and momentum of interplanetary dust particles -between the Earth and Venus. These measurements were concerned with the -particles’ direction and distance from the Sun, the momentum with -respect to the spacecraft, the nature of any concentrations of the dust -in streams, variations in cosmic dust flux with distance from the Earth -and Venus, and the possible effects on manned flight. - -Mariner’s cosmic dust instrument could detect a particle as small as -something like a billionth of a gram, or about five-trillionths of a -pound. This type of sensor had been used on rockets even before Explorer -I. It had yielded good results on Pioneer I in the region between the -Earth and the Moon. The instrument was a 55-square-inch acoustical -detector plate, or sounding board, made of magnesium. A crystal -microphone was attached to the center of the plate. The instrument could -detect both low- and high-momentum particles and also provide a rough -idea of their direction of travel. - -The dust particle counters were read once each 37 seconds during the -cruise mode. This rate was increased to once each 20 seconds during the -encounter with Venus. - -The instrument was attached to the top of the basic hexagonal structure; -it weighed 1.85 pounds, and consumed only 0.8 watt of power. - - -SOLAR PLASMA EXPERIMENT - -In order to investigate the phenomena associated with the movement of -plasma (charged particles of low energy and density streaming out from -the Sun to form the so-called “solar wind”) in interplanetary space, -Mariner carried a solar plasma spectrometer that measured the flux and -energy spectrum of positively charged plasma components with energies in -the range 240 to 8400 volts. The extremely sensitive plasma detector -unit was open to space, consumed 1 watt of power, and consisted of four -basic elements: curved electrostatic deflection plates and collector -cup, electrometer, a sweep amplifier, and a programmer. - -The curved deflector plates formed a tunnel that projected from the -chassis on the spacecraft hexagon in which the instrument was housed. -Pointed toward the Sun, the gold-plated magnesium deflector plates -gathered particles from space. Since the walls of the tunnel each -carried different electrical charges, only particles with just the -correct energy and speed could pass through and be detected by the -collector cup without striking the charged walls. A sensitive -electrometer circuit then measured the current generated by the flow of -the charged particles reaching the cup. - -The deflection plates were supplied by amplifier-generated voltages -which were varied in 10 steps, each lasting about 18 seconds, allowing -the instrument to measure protons with energies in the 240 to 8,400 -electron volt range. The programmer switched in the proper voltage and -resistances. - - -HIGH-ENERGY RADIATION EXPERIMENT - -Mariner carried an experiment to measure high-energy radiation in space -and near Venus. The charged particles measured by Mariner were primarily -cosmic rays (protons or the nuclei of hydrogen atoms), alpha particles -(nuclei of helium atoms), the nuclei of other heavier atoms, and -electrons. The study of these particles in space and those which might -be trapped near Venus was undertaken in the hope of a better -understanding of the dynamics of the solar system and the potential -hazards to manned flight. - -The high-energy radiation experiment consisted of an ionization chamber -and detectors measuring particle flux (velocity times density), all -mounted in a box measuring 6 × 6 × 2 inches and weighing just under 3 -pounds. The box was attached halfway up the spacecraft superstructure in -order to isolate the instruments as much as possible from secondary -emission particles produced when the spacecraft was struck by cosmic -rays, and to prevent the spacecraft from blocking high-energy radiation -from space. - -The ionization chamber had a stainless steel shell 5 inches in diameter, -with walls only 1/100-inch thick. The chamber was filled with argon gas -into which was projected a quartz fibre next to a quartz rod. - -A charged particle entering the chamber would leave a wake of ions in -the argon gas. Negative ions accumulated on the rod, reducing the -potential between the rod and the spherical shell, eventually causing -the quartz fibre to touch the rod. This action discharged the rod, -producing an electrical pulse which was amplified and transmitted to the -Earth. The rod was then recharged and the fibre returned to its original -position. - -In order to penetrate the walls of the chamber, protons required an -energy of 10 million electron volts (Mev), electrons needed 0.5 Mev, and -alpha particles 40 Mev. - -The particle flux detector incorporated three Geiger-Mueller tubes, two -of which formed a companion experiment to the ionization chamber; each -generated a current pulse whenever a charged particle was detected. One -tube was shielded by an 8/1,000-inch-thick stainless steel sleeve, the -other by a 24/1,000-inch-thick electron-stopping beryllium shield. Thus, -the proportion of particles could be determined. - -The third Geiger-Mueller tube was an end-window Anton-type sensor with a -mica window that admitted protons with energies greater than 0.5 Mev and -electrons, 40,000 electron volts. A magnesium shield around the rest of -the tube enabled the instrument to determine the direction of particles -penetrating only the window. - -The three Geiger-Mueller tubes protruded from the box on the -superstructure of the spacecraft. The end-window tube was inclined 20 -degrees from the others and 70 degrees from the spacecraft-Sun line -since it had to be shielded from direct solar exposure. - - -THE MAGNETOMETER - -Mariner carried a magnetometer to measure the magnetic field in -interplanetary space and in the vicinity of Venus. Lower sensitivity -limit of the instrument was about 5 gamma. A gamma is a unit of magnetic -measurement and is equal to 10⁻⁵ or 1/100,000 oersted, or 1/30,000 of -the Earth’s magnetic field at the equator. The nails in one of your -shoes would probably produce a field of about 1 gamma at a distance of -approximately 4 feet. - -Housed in a 6- × 3-inch metal cylinder, the instrument consisted of -three magnetic core sensors, each aligned on a different axis to read -the three magnetic field components and having primary and secondary -windings. The presence of a magnetic field altered the current in the -secondary winding in proportion to the strength of the field -encountered. - -The magnetometer was attached near the top of the superstructure, just -below the omni-antenna, in order to remove it as far as possible from -any spacecraft components having magnetic fields of their own. - -An auxiliary coil was wound around each of the instrument’s magnetic -sensor cores to compensate for permanent magnetic fields existing in the -spacecraft itself. These spacecraft fields were measured at the -magnetometer before launch and, in flight, the auxiliary coils carried -currents of sufficient strength to cancel out the spacecraft’s magnetic -fields. - -The magnetometer reported almost continuously on its journey and for 20 -days after encounter. During the encounter, observations were made each -20 seconds on each of the three components of the magnetic field. - - -MICROWAVE RADIOMETER - -A microwave radiometer on board Mariner II was designed to scan Venus -during encounter at two wavelengths: 13.5 and 19 millimeters. The -radiometer was intended to help settle some of the controversies about -the origin of the apparently high surface temperature emanating from -Venus, and the value of the surface temperature. - -The equipment included a 19-inch-diameter parabolic antenna mounted -above the basic hexagonal structure on a swivel driven in a 120-degree -scanning motion by a motor. The radiometer electronics circuits were -housed behind the antenna dish. The antenna was equipped with a -diplexer, which allowed it to receive both wavelengths at once without -interference, and to compare the signals emanating from the two -reference horns with those from the planet. The reference horns were -pointed away from the main antenna beam so they would look into deep -space as Mariner passed Venus. This feature allowed the antenna to -“bring in” a reference temperature of approximately absolute zero during -encounter. - -The microwave radiometer was to be turned on 10 hours before the -encounter began. An electric motor was then to start a scanning or -“nodding” motion of 120 degrees at the rate of 1 degree per second. Upon -radiometer contact with the planet, this scanning rate would be reduced -to 1/10 degree per second as long as the planetary disk was scanned. A -special command system in the data conditioning system would reverse or -normalize the direction of scan as the radiometer reached the edge or -limb of the planet. - -The signals from the antenna and the reference horns were to be -processed and the data handled in a receiver, located behind the -antenna, which measured the difference between the signals from Venus -and the reference signals from space. The information was then to be -telemetered to the Earth. - -The microwave radiometer was automatically calibrated twenty-three times -during the mission by a sequence originating in the data conditioning -system, so that the correct functioning of the instrument could be -determined before the encounter with Venus. - - -INFRARED RADIOMETER - -The infrared radiometer was a companion experiment to the microwave -instrument and was rigidly mounted to the microwave antenna so that both -radiometers would look at the same area of Venus with the same scanning -rate. The instrument detected radiation in the 8 to 9 and 10 to 10.8 -micron regions of the infrared spectrum. - -The infrared radiometer had two optical sensors. As the energy entered -the system, it was “chopped” by a rotating disk, alternately passing or -comparing emissions from Venus and from empty space. The beam was then -split by a filter into the two wavelength regions. The output was then -detected, processed, and transmitted to the Earth. - -The infrared radiometer measured 6 inches by 2 inches, weighed 2.7 -pounds, and consumed 2 watts of power. The instrument was equipped with -a calibration plate which was mounted on a superstructure truss adjacent -to the radiometer. - - -MARINER’S SCIENTIFIC OBJECTIVES - -Equipped with these instruments and with the mechanism for getting the -measurements back to Earth, Mariner II was prepared to look for the -answers to some of the questions inherent in its over-all mission -objectives: - - 1. The investigation of interplanetary space between the Earth and - Venus, measuring such phenomena as the cosmic dust, the - mysterious plasma or solar winds, high-energy cosmic rays from - space outside our solar system, charged particles from the - Sun, and the magnetic fields of space. - 2. The experiments to be performed near Venus (at about 21,150 miles - out from the surface) in an effort to understand its magnetic - fields, radiation belts, the temperature and composition of - its clouds, and the temperature and conditions on the surface - of the planet. - - - - - CHAPTER 9 - THE LEGACY OF MARINER - - -If intelligent life had existed on Venus on the afternoon of the Earth’s -December 14, 1962, and if it could have seen through the clouds, it -might have observed Mariner II approach from the night side, drift down -closer, cross over to the daylight face, and move away toward the Sun to -the right. The time was the equivalent of 12:34 p.m. along the Pacific -Coast of the United States, where the spacecraft was being tracked. - -Mariner II had reached the climax of its 180-million-mile, 109-day trip -through space. The 35-minute encounter with Venus would tell Earth -scientists more about our sister planet than they had been able to learn -during all the preceding centuries. - - -SPACE WITHOUT DUST? - -Before Mariner, scientists theorized about the existence of clouds of -cosmic dust around the Sun. A knowledge of the composition, origin, and -the dynamics of these minute particles is necessary for study of the -origins and evolution of the solar system. - -Tiny particles of cosmic dust (some with masses as low as 1.3 × 10⁻¹⁰ -gram or about one-trillionth of a pound) were thought to be present in -the solar system and have been recorded by satellites in the near-Earth -regions. - -These microcosmic particles could be either the residue left over after -our solar system was formed some 5 billion years ago, possibly by -condensation of huge masses of gas and dust clouds; or, the debris -deposited within our system by the far-flung and decaying tails of -passing comets; or, the dust trapped from galactic space by the magnetic -fields of the Sun and the planets. - -Analysis of the more than 1,700 hours of cosmic dust detector data -recovered from the flight of Mariner II seems to indicate that in the -region between the Earth and Venus the concentration of tiny cosmic dust -particles is some ten-thousand times less than that observed near the -Earth. - -During the 129 days (including the post-encounter period) of Mariner’s -mission, the data showed only one dust particle impact which occurred in -deep space and not near Venus. Equivalent experiments near Earth (on -board Earth satellites) have yielded over 3,700 such impacts within -periods of approximately 500 hours. The cause of this heavy near-Earth -concentration, the exact types of particles, and their source are still -unknown. - -The cosmic dust experiment performed well during the Mariner mission. -Although some calibration difficulty was observed about two weeks before -the Venus encounter, possibly caused by overheating of the sensor -crystal, there was no apparent effect in the electronic circuits. - - -THE UBIQUITOUS SOLAR WIND - -For some time prior to Mariner, scientists postulated the existence of a -so-called plasma flow or “solar wind” streaming out from the Sun, to -explain the motion of comet tails (which always point away from the Sun, -perhaps repelled by the plasma), geomagnetic storms, aurorae, and other -such disturbances. (Plasma is defined as a gas in which the atoms are -dissociated into atomic nuclei and electrons, but which, as a whole, is -electrically neutral.) - -The solar wind was thought to drastically alter the configuration of the -Sun’s external magnetic field. Plasma moving at extreme velocities is -able to carry with it the lines of magnetic force originating in the -Sun’s corona and to distort any fields it encounters as it moves out -from the Sun. - -It was believed that these moving plasma currents are also capable of -altering the size of a planet’s field of magnetic flux. When this -happens, the field on the sunlit face of the planet is compressed and -the dark side has an elongated expansion of the field. For example, the -outer boundary of the Earth’s magnetic field is pushed in by the solar -wind to about 40,000 miles from the Earth on the sunward side. On the -dark side, the field extends out much farther. - -The solar wind was also known to have an apparent effect on the movement -of cosmic rays. As the Sun spots increase in the regular 11-year cycle, -the number of cosmic rays reaching the Earth from outside our solar -system will decrease. - -Mariner II found that streams of plasma are constantly flowing out from -the Sun. This fluctuating, extremely tenuous solar wind seems to -dominate interplanetary space in our region of the solar system. The -wind moves at velocities varying from about 200 to 500 miles per second -(about 720,000 to 1,800,000 miles per hour), and measures up to perhaps -a million degrees Fahrenheit (within the subatomic structure). - -With the solar plasma spectrometer working at ten different energy -levels, Mariner required 3.7 minutes to run through a complete energy -spectrum. During the 123 days, when readings were made, a total of -40,000 such spectra were recorded. Plasma was monitored on 104 of those -123 days, and on every one of the spectra, the plasma was always -present. - -Mariner showed that the energies of the particles in the solar winds are -very low, on the order of a few hundred or few thousand electron volts, -as compared with the billions and trillions of electron volts measured -in cosmic radiation. - -The extreme tenuousity or low density of the solar wind is difficult to -comprehend: about 10 to 20 protons (hydrogen nuclei) and electrons per -cubic inch. But despite the low energy and density, solar wind particles -in our region of the solar system are billions of times more numerous -than cosmic rays and, therefore, the total energy content of the winds -is much greater than that of the cosmic rays. - -Mariner found that when the surface of the Sun was relatively inactive, -the velocity of the wind was a little less than 250 miles per second and -the temperature a few hundred thousand degrees. The plasma was always -present, but the density and the velocity varied. Flare activity on the -Sun seemed to eject clouds of plasma, greatly increasing the velocity -and density of the winds. Where the particles were protons, their -energies ranged from 750 to 2,500 electron volts. - -The experiment also showed that the velocity of the plasma apparently -undergoes frequent fluctuations of this type. On approximately twenty -occasions, the velocity increased within a day or two by 20 to 100%. -These disturbances seemed to correlate well with magnetic storms -observed on the Earth. In several cases, the sudden increase in the -solar plasma flux preceded various geomagnetic effects observed on the -Earth by only a short time. - -The Mariner solar plasma experiment was the first extensive measurement -of the intensity and velocity spectrum of solar plasma taken far enough -from the Earth’s field so that the Earth would have no effect on the -results. - - -HIGH-ENERGY PARTICLES: FATAL DOSAGE? - -Speculation has long existed as to the amount of high-energy radiation -(from cosmic rays and particles from the Sun with energies in the -millions of electron volts) present within our solar system and as to -whether exposure would be fatal to a human space traveler. - -This high-energy type of ionizing radiation is thought to consist of the -nuclei of such atoms as hydrogen and helium, and of electrons, all -moving very rapidly. The individual particles are energetic enough to -penetrate considerable amounts of matter. The concentration of these -particles is apparently much lower than that of low-energy plasma. - -The experiments were designed to detect three types of high-energy -radiation particles: the cosmic rays coming from outside the solar -system, solar flare particles, and radiation trapped around Venus (as -that which is found in the Earth’s Van Allen Belt). - -These high-energy radiation particles (also thought to affect aurorae -and radio blackouts on the Earth) measure from about one hundred -thousand electron volts up to billions of volts. The distribution of -this energy is thought to be uniform outside the solar system and is -assumed to move in all directions in a pattern remaining essentially -constant over thousands of years. - -Inside the solar system, the amount of such radiation reaching the Earth -is apparently controlled by the magnetic fields found in interplanetary -space and near the Earth. - -The number of cosmic rays changes by a large amount over the course of -an 11-year Sun-spot cycle, and below a certain energy level (5,000 Mev) -few cosmic rays are present in the solar system. They are probably -deflected by plasma currents or magnetic fields. - -Mariner’s charged particles experiment indicated that cosmic radiation -(bombardment by cosmic rays), both from galactic space and those -particles originating in the Sun, would not have been fatal to an -astronaut, at least during the four-month period of Mariner’s mission. - -The accumulated radiation inside the counters was only 3 roentgens, and -during the one solar storm recorded on October 23 and 24, the dosage -measured only about ¼ roentgen. In other words, the dosage amounts to -about one-thousandth of the usually accepted “half-lethal” dosage, or -that level at which half of the persons exposed would die. An astronaut -might accept many times the dosage detected by Mariner II without -serious effects. - -The experiment also showed little variation in density of charged -particles during the trip, even with a 30% decrease in distance from the -Sun, and no apparent increase due to magnetically trapped particles or -radiation belts near Venus as compared with interplanetary space. -However, these measurements were made during a period when the Sun was -slowly decreasing in activity at the end of an 11-year cycle. The Sun -spots will be at a minimum in 1964-1965, when galactic cosmic rays will -sharply increase. Further experiments are needed to sample the charged -particles in space under all conditions. - -The lack of change measured by the ionization chamber during the mission -was significant; the cosmic-ray flux of approximately 3 particles per -square centimeter per second throughout the flight was an unusually -constant value. A clear increase in high-energy particles (10 Mev to -about 800 Mev) emitted by the Sun was noted only once: a flare-up -between 7:42 and 8:45 a.m., PST, October 23. The ionization chamber -reading began to increase before the flare disappeared. From a -background reading of 670 ion pairs per cubic centimeter per second per -standard atmosphere, it went to a peak value of 18,000, varied a bit, -and remained above 10,000 for 6 hours before gradually decreasing over a -period of several days. Meanwhile, the flux of the particles detected by -the Geiger counter rose from the background count of 3 to a peak of 16 -per square centimeter per second. Ionization thus increased much more -than the number of particles, indicating to the scientists that the -high-energy particles coming from the Sun might have had much lower -average energies than the galactic cosmic rays. - - [Illustration: _Data obtained by microwave radiometer are - illustrated at left; results of infrared radiometer experiment are - shown at right. Note how moving spacecraft sees more of atmosphere - along limb or edge of planet, less in center._] - -In contrast, the low-energy experiment detected the October 23 event, -and eight or ten others not seen by the high-energy detectors. These -must have been low-penetrating particles excluded by the thicker walls -of the high-energy instrument. These particles were perhaps protons -between 0.5 and 10 Mev or electrons between 0.04 and 0.5 Mev. - -At 20,000 miles from the Earth, the rate at which high-energy particles -have been observed has been recorded at several thousand per second. -With Mariner at approximately the same distance from Venus, the average -was only one particle per second, as it had been during most of the -month of November in space. Such a rate would indicate a low planetary -magnetic field, or one that did not extend out as far as Mariner’s -21,598-mile closest approach to the surface. - -Mariner II measured and transmitted data in unprecedented quantity and -quality during the long trip. In summary, Mariner showed that, during -the measuring period, particles were numerous in the energy ranges from -a few hundred to 1,000 electron volts. Protons in the range 0.5 to 10 -Mev were not numerous, but at times the flux (density) was several times -that of cosmic rays. - -Almost no protons were shown in the 10 to 800 Mev range, except during -solar flares when the particles in this range were numerous. Above 800 -Mev (primarily those cosmic rays entering interplanetary space from -outside the solar system) the number decreased rapidly as the energy -increased, the average total being about 3 per centimeter per second. - -During one 30-day period in November and December, the low-energy -counter saw only two small increases in radiation intensity. At this -time, the mean velocity of the solar wind was considerably lower than -during September and October. This might suggest that high-velocity -plasma and low-energy cosmic rays might both originate from the same -solar source. - - -A MAGNETIC FIELD? - -Prior to the Mariner II mission, no conclusive evidence had ever been -presented concerning a Venusian magnetic field and nothing was known -about possible fluid motions in a molten core or other hypotheses -concerning the interior of the planet. - -Scientists assumed that Venus had a field somewhat similar to the -Earth’s, although possibly reduced in magnitude because of the -apparently slow rate of rotation and the pressure of solar plasma. Many -questions had also been raised concerning the nature of the atmosphere, -charged particles in the vicinity of the planet, magnetic storms, and -aurorae. Good magnetometer data from Mariner II would help solve some of -these problems. - -Mariner’s magnetometer experiment also sought verification of the -existence and nature of a steady magnetic field in interplanetary space. -This would be important in understanding the charged particle balance of -the inner solar system. Other objectives of the experiment were to -establish both the direction and the magnitude of long-period -fluctuations in the interplanetary magnetic field and to study solar -disturbances and such problems in magnetohydrodynamics (the study of the -motion of charged particles and their surrounding magnetic fields) as -the existence and effect of magnetized and charged plasmas in space. - -The strength of a planet’s field is thought to be closely related to its -rate of rotation—the slower the rotation, the weaker the field. As a -consequence, if Venus’ field is simple in structure like the Earth’s, -the surface field should be 5 to 10% that of the Earth. If the structure -of the field is complex, the surface field in places might exceed the -Earth’s without increasing the field along Mariner’s trajectory to -observable values. - -Most of the phenomena associated with the Earth’s magnetic field are -likely to be significantly modified or completely absent in and around -Venus. Auroral displays and the trapping of charged particles in -radiation belts such as our Van Allen would be missing. The field of the -Earth keeps low- and moderate-energy cosmic rays away from the top of -the atmosphere, except in the polar regions. The cosmic ray flux at the -top of Venus’ atmosphere is likely to correspond everywhere to the high -level found at the Earth’s poles. - - [Illustration: _As it encountered Venus, Mariner II made three scans - of the planet._] - - SUN - DIRECTION OF SCAN - DATA READINGS (18 TOTAL) - -In contrast to Venus, Jupiter, which is ten times larger in mass and -volume and rotates twice as fast as the Earth, has a field considerably -stronger than the Earth’s. The Moon has a field on the sunlit side -(according to Russian measurements) which, because of the Moon’s slow -rotation rate, is less than ⅓ of 1% of the Earth’s at the Equator. Thus, -a planet’s rotation, if at a less rapid rate than the Earth’s, seems to -produce smaller magnetic fields. This theory is consistent with the idea -of a planetary magnetic field resulting from the dynamo action inside -the molten core of a rotating planet. - -The Sun, on the whole, has a fairly regular dipole field. Superimposed -on this are some very large fields associated with disturbed regions -such as spots or flares, which produce fields of very great intensities. - -These solar fields are drawn out into space by plasma flow. Although -relatively small in magnitude, these fields are an important influence -on the propagation of particles. And the areas in question are very -large—something on the order of an astronomical unit. - -Mariner II seemed to show that, in space, a generally quiet -magnetic-field condition was found to exist, measuring something less -than 10 gamma and fluctuating over periods of 1 second to 1 minute. - -As Mariner made its closest approach to Venus, the magnetometer saw no -significant change, a condition also noted by the radiation and solar -plasma detectors. The magnetic field data looked essentially as they had -in interplanetary space, without either fluctuations or smooth changes. - -The encounter produced no slow changes, nor was there a continuous -fluctuation as in the interplanetary regions. There was no indication of -trapped particles or near-Venus modification in the flow of solar -plasma. - -On the Earth’s sunny side, a definite magnetic field exists out to -40,000 miles, and on the side away from the Sun considerably farther. If -Venus’ field had been similar to the Earth’s, a reading of 100 to 200 -gamma, a large cosmic-ray count, and an absence of solar plasma should -have been shown, but none of these phenomena were noted by Mariner. - -These results do not prove that Venus definitely has no magnetic field, -but only that it was not measurable at Mariner’s 21,598-mile point of -closest approach. The slow rotation rate and the pressure of the solar -winds probably combine to limit the field to a value one tenth of the -Earth’s. Since Mariner passed Venus on the sunlit side, readings are -required on the dark side in order to confirm the condition of the -magnetic field on that side of the planet, which normally should be -considerably extended. - - -THE SURFACE: HOW HOT? - -Before Mariner, scientists had offered two main theories about the -surface of Venus: It had either an electrically charged ionosphere -causing false high-temperature readings on Earth instruments despite a -cool surface, or a hot surface with clouds becoming increasingly colder -with altitude. - -The cool-surface theory supposed an ionosphere with a layer of electrons -having a density thousands of times that of the Earth’s upper -atmosphere. Microwave radiations from this electrical layer would cause -misleading readings on Earth instruments. As a space probe scanned -across such an atmosphere, it would see the least amount of charged -ionosphere when looking straight down, and the most concentrated amount -while scanning the limb or edge. In the latter case, it would be at an -angle and would show essentially a thickening effect of the atmosphere -because of the curvature of the planet. - -As the probe approached the edge, the phenomenon known as “limb -brightening” would occur, since the instruments would see more of the -electron-charged ionosphere and little if any of the cooler surface. The -temperature readings would, therefore, be correspondingly higher at the -limbs. - -The other theory, held by most scientists, visualized a hot surface on -Venus, with no heavy concentration of electrons in the atmosphere, but -with cooler clouds at higher altitudes. Thus, the spacecraft would look -at a very hot planet from space, covered by colder, thick clouds. -Straight down, the microwave radiometer would see the hot surface -through the clouds. When approaching the limb, the radiations would -encounter a thicker concentration of atmosphere and might not see any of -the hot surface. This condition, “limb darkening,” would be -characterized by temperatures decreasing as the edges of the planet were -approached. - -An instrument capability or resolution much higher than that available -from the Earth was required to resolve the limb-brightening or -limb-darkening controversy. Mariner’s radiometer would be able to -provide something like one hundred times better resolution than the -Earth-based measurements. - -At 11:59 a.m., PST, on December 14, 1962, Mariner’s radiometers began to -scan the planet Venus in a nodding motion at a rate of 0.1 degree per -second and reaching an angular sweep of nominally 120 degrees. The -radiometers had been switched on 6½ hours before the encounter with -Venus and they continued to operate for another hour afterward. - -The microwave radiometer looked at Venus at a wavelength of 13.5 -millimeters and 19 millimeters. The 13.5-millimeter region was the -location of a microwave water absorption band within the electromagnetic -spectrum, but it was not anticipated that it would detect any water -vapor on Venus. These measurements would allow determination of -atmospheric radiation, averaging the hot temperatures near the surface, -the warmer clouds at lower levels, and the lower temperatures found in -the high atmosphere. If the atmosphere were a strong absorber of -microwave energy at 13.5 millimeters, only the temperature of the upper -layers would be reported. - -Unaffected by water vapor, 19-millimeter radiations could be detected -from deeper down into the cloud cover, perhaps from near or at the -planet’s surface. Large temperature differences between the 19- and 13.5 -millimeter readings would indicate the relative amount of water vapor -present in the atmosphere. The 19-millimeter radiations would also test -the limb-brightening theory. - -During its scanning operation, Mariner telemetered back to Earth about -18 digital data points, represented as voltage fluctuations in relation -to time. The first scan was on the dark side, going up on the planet: -the distance from the surface was 16,479 miles at midscan, and the -brightness temperature was 369 degrees F. The second scan nearly -paralleled the terminator (junction of light and dark sides) but crossed -it going down; it was made from 14,957 miles at midscan and showed a -temperature of 566 degrees F. The final scan, 13,776 miles at midpoint, -showed 261 degrees F as it swept across the sunlit side of Venus in an -upward direction. - -The brightness temperature recorded by Mariner’s radiometer is not the -true temperature of the surface. It is derived from the amount of light -or radio energy reflected or emitted by an object. If the object is not -a perfect light emitter, as most are not, then the light and radio -energy will be some fraction of that returned from a 100% efficient -body, and the object is really hotter than the brightness measurement -shows. Thus, the brightness temperature is a minimum reading and in this -case, was lower than the actual surface temperature. - -Mariner’s microwave radiometer showed no significant difference between -the light and dark sides of Venus and, importantly, higher temperatures -along the terminator or night-and-day line of the planet. These results -would indicate no ionosphere supercharged with electrons, but a definite -limb-darkening effect, since the edges were cooler than the center of -the planet. - -Therefore, considering the absorption characteristics of the atmosphere -and the emissivity factor derived from earlier JPL radar experiments, a -fairly uniform 800 degrees F was estimated as a preliminary temperature -figure for the entire surface. - -Venus is, indeed, a very hot planet. - - -CLOUD TEMPERATURES: THE INFRARED READINGS - -Mariner II took a close look at Venus’ clouds with its infrared -radiometer during its 35-minute encounter with the planet. This -instrument was firmly attached to the microwave radiometer so the two -devices would scan the same areas of Venus at the same rate and the data -would be closely correlated. This arrangement was necessary to produce -in effect a stereoscopic view of the planet from two different regions -of the spectrum. - -Because astronomers have long conjectured about the irregular dark spots -discernible on the surface of Venus’ atmosphere, data to resolve these -questions would be of great scientific interest. If the spots were -indeed breaks in the clouds, they would stand out with much better -definition in the infrared spectrum. If the radiation came from the -cloud tops, there would be no breaks and the temperatures at both -frequencies measured by the infrared radiometer would follow essentially -the same pattern. - -The Venusian atmosphere is transparent to the 8-micron region of the -spectrum except for clouds. In the 10-micron range, the lower atmosphere -would be hidden by carbon dioxide. If cloud breaks existed, the 8-micron -emissions would come from a much lower point, since the lower atmosphere -is fairly transparent at this wavelength. If increasing temperatures -were shown in this region, it might mean that some radiation was coming -up from the surface. - -As a result of the Mariner II mission, scientists have hypothecated that -the cold cloud cover could be about 15 miles thick, with the lower base -beginning about 45 miles above the surface, and the top occurring at 60 -miles. In this case, the bottom of the cloud layer could be -approximately 200 degrees F; at the top, the readings vary from about -minus 30 degrees F in the center of the planet to temperatures of -perhaps minus 60 degrees to minus 70 degrees F along the edges. This -temperature gradient would verify the limb-darkening effect seen by the -microwave radiometer. - -At the center of Venus, the radiometer saw a thicker, brighter, hotter -part of the cloud layer; at the limbs, it could not see so deeply and -the colder upper layers were visible. Furthermore, the temperatures -along the cloud tops were approximately equally distributed, indicating -that both 8- and 10-micron “channels” penetrated to the same depth and -that both were looking at thick, dense clouds quite opaque to infrared -radiation. - -Both channels detected a curious feature along the lower portion of the -terminator, or the center line between the night and day sides of the -planet. In that region, a spot was shown that was apparently about 20 -degrees F colder than the rest of the cloud layer. Such an anomaly could -result from higher or more opaque clouds, or from such an irregularity -as a hidden surface feature. A mountain could force the clouds upward, -thus cooling them further, but it would have to be extremely high. - -The data allow scientists to deduce that not enough carbon dioxide was -present above the clouds for appreciable absorption in the 10-micron -region. This effect would seem to indicate that the clouds are thick and -that there is little radiation coming up from the surface. And, if -present, water vapor content might be 1/1,000 of that in the Earth’s -atmosphere. - -Since the cloud base is apparently at a very high temperature, neither -carbon dioxide nor water is likely to be present in quantity. Rather, -the base of the clouds must contain some component that will condense in -small quantities and not be spectroscopically detected. - -As a result of the two radiometer experiments, the region below the -clouds and the surface itself take on better definition. Certainly, -heat-trapping of infrared radiation, or a “greenhouse” effect, must be -expected to support the 800 degree F surface temperature estimated from -the microwave radiometer data. Thus, a considerable amount of -energy-blanketing carbon dioxide must be present below the cloud base. -It is thought that some of the near-infrared sunlight might filter -through the clouds in small amounts, so that the sky would not be -entirely black, at least to human eyes, on the sunlit side of Venus. -There also may be some very small content of oxygen below the clouds, -and perhaps considerable amounts of nitrogen. - -The atmospheric pressure on the surface might be very high, about 20 -times the Earth’s atmosphere or more (equivalent to about 600 inches of -mercury, compared with our 30 inches). The surface, despite the high -temperature, is not likely to be molten because of the roughness index -seen in the earlier radar experiments, and other indicators. However, -the possibility of small molten metal lakes cannot be totally ignored. - -The dense, high-pressure atmosphere and the heat-capturing greenhouse -effect could combine over long periods of time to carry the extremely -high temperature around to the dark side of Venus, despite the slow rate -of rotation, possibly accounting for the relatively uniform surface -temperatures apparently found by Mariner II. - - -THE RADAR PROFILE: MEASUREMENTS FROM EARTH - -In 1961, the Jet Propulsion Laboratory conducted a series of experiments -from its Goldstone, California, DSIF Station, successfully bouncing -radar signals off the planet Venus and receiving the return signal after -it had travelled 70 million miles in 6½ minutes. - -In order to complement the Mariner mission to Venus, the radar -experiments were repeated from October to December, 1962 (during the -Mariner mission), using improved equipment and refined techniques. As in -1961, the experiments were directed by W. K. Victor and R. Stevens. - -The 1961 experiments used two 85-foot antennas, one transmitting 13 -kilowatts of power at 2,388 megacycles, the other receiving the return -signal after the round trip to and from Venus. The most important result -was the refinement of the astronomical unit—the mean distance from the -Earth to the Sun—to a value of 92,956,200 ±300 miles. - -Around 1910, the astronomical unit, plotted by classical optical -methods, was uncertain to 250,000 miles. Before the introduction of -radar astronomy techniques such as those used at Goldstone, scientists -believed that the astronomical unit was known to within 60,000 miles, -but even this factor of uncertainty would be intolerable for planetary -exploration. - -In radar astronomy, the transit time of a radio signal moving at the -speed of light (186,000 miles per second) is measured as it travels to a -planet and back. In conjunction with the angular measurement techniques -used by earlier investigators, this method permits a more precise -calculation of the astronomical unit. - -Optical and radar measurements of the astronomical unit differ by 50,000 -miles. Further refinement of both techniques should lessen the -discrepancy between the two values. - -The 1961 tests also established that Venus rotates at a very slow rate, -possibly keeping the same face toward the Sun at all times. The -reflection coefficient of the planet was estimated at 12%, a bright -value similar to that of the Earth and contrasted with the Moon’s 2%. -The average dielectric constant (conductivity factor) of the surface -material seemed to be close to that of sand or dust, and the surface was -reported to be rough at a wavelength of 6 inches. - -The surface roughness was confirmed in 1962. Since it is known that a -rough surface will scatter a signal, the radar tests were observed for -such indications. Venus had a scattering effect on the radar waves -similar to the Moon’s, probably establishing the roughness of the -Venusian surface as more or less similar to the lunar terrain. - -Some of the most interesting work was done in reference to the rotation -rate of Venus. A radar signal will spread in frequency on return from a -target planet that is rotating and rough enough to reflect from a -considerable area of its surface. The spread of 5 to 10 cycles per -second noted on the Venus echo would suggest a very slow rotation rate, -perhaps keeping the same face toward the Sun, or possibly even in a -retrograde direction, opposite to the Earth’s. - -In the Goldstone 1962 experiments, Venus was in effect divided into -observation zones and the doppler effect or change in the returned -signal from these zones was studied. The rate of rotation was derived -from three months of sampling with this radar mapping technique. Also, -the clear, sharp tone characteristic of the transmitted radar signal was -altered on return from Venus into a fuzzy, indistinct sound. This effect -seemed to confirm the slow retrograde rotation (as compared with the -Earth) indicated by the radar mapping and frequency change method. - -In addition to these methods of deducing the slow rotation rate, two -other phenomena seemed to verify it: a slowly fluctuating signal -strength, and the apparent progression of a bright radar spot across -from the center of Venus toward the outside edge. - -As a result, JPL scientists revised their 1961 estimate of an equal -Venusian day and year consisting of 225 Earth days. The new value for -Venus’ rotation rate around its axis is 230 Earth days plus or minus 40 -to 50 days, and in a retrograde direction (opposite to synchronous or -Sun-facing), assuming that Venus rotates on an axis perpendicular to the -plane of its orbit. - -Thus, on Venus the Sun would appear to rise in the west and cross to the -east about once each Venusian year. If the period were exactly 225 days -retrograde, the stars would remain stationary in the sky and Venus would -always face a given star rather than the Sun. - -A space traveller hovering several million miles directly above the Sun -would thus see Venus as almost stopped in its rotation and possibly -turning very slowly clockwise. All the other planets of our system -including the Earth, rotate counterclockwise, except Uranus, whose axis -is almost parallel to the plane of its orbit, making it seem to roll -around the Sun on its side. The rotation direction of distant Pluto is -unknown. - -The Goldstone experiments also studied what is known as the Faraday -rotation of the plane of polarization of a radio wave. The results -indicated that the ionization and magnetic field around Venus are very -low. These data tend to confirm those gathered by Mariner’s experiments -close to the planet. - -The mass of Venus was another value that had never been precisely -established. The mass of planetary bodies is determined by their -gravitational effect on other bodies, such as satellites. Since Venus -has no known natural satellite or moon, Mariner, approaching closely -enough to “feel” its gravity, would provide the first opportunity for -close measurement. - -The distortion caused by Venus on Mariner’s trajectory as the spacecraft -passed the planet enabled scientists to calculate the mass with an error -probability of 0.015%. The value arrived at is 0.81485 of the mass of -the Earth, which is known to be approximately 13.173 septillion -(13,173,000,000,000,000,000,000,000) pounds. Thus, the mass of Venus is -approximately 10.729 septillion (10,729,408,500,000,000,000,000,000) -pounds. - -In addition to these measurements, the extremely precise tracking system -used on Mariner proved the feasibility of long-range tracking in space, -particularly in radial velocity, which was measured to within 1/10 of an -inch per second at a distance of about 54 million miles. - -As the mission progressed, the trajectory was corrected with respect to -Venus to within 10 miles at encounter. An interesting result was the -very precise location of the Goldstone and overseas tracking stations of -the DSIF. Before Mariner II, these locations were known to within 100 -yards. After all the data have been analyzed, these locations will be -redefined or “relocated” to within an error of only 20 yards. - -Mariner not only made the first successful journey to Venus—it also -helped pinpoint spots in the Californian and Australian deserts and the -South African veldt with an accuracy never before achieved. - - - - - CHAPTER 10 - THE NEW LOOK OF VENUS - - -The historic mission of Mariner II to the near-vicinity of Venus and -beyond has enabled scientists to revise many of their concepts of -interplanetary space and the planet Venus. - -The composite picture, taken from the six experiments aboard the -spacecraft and the data from the DSIF radar experiments of 1961 and 1962 -revealed the following: - - -—Interplanetary space between the Earth and Venus, at least as it was - during the four months of Mariner’s mission, had a cosmic dust density - some ten-thousand times lower than the region immediately surrounding - the Earth. - -—During this period, the extremely tenuous, widely fluctuating solar - winds streamed continually out from the Sun, at velocities ranging - from 200 to 500 miles per second. - -—An astronaut travelling through these regions in the last quarter of - 1962 would not have been seriously affected by the cosmic and - high-energy radiation from space and the Sun. He could easily have - survived many times the amount of radiation detected by Mariner’s - instruments. - -—111 - -—The astronomical unit, as determined by radar, the yardstick of our - solar system, stands at 92,956,200, plus or minus 300 miles. - -—The mass of Venus in relation to the Earth’s is 0.81485, with an error - probability of 0.015%. - -—The rotation rate of Venus is quite slow and is now estimated as equal - to 230 Earth days, plus or minus 40 to 50 days. The rotation might be - retrograde, clockwise with respect to a Sun-facing reference, with the - Sun rising in the west and setting in the east approximately one - Venusian year later. The planet seems to remain nearly star-fixed - rather than permanently oriented with one face to the Sun. - -—Venus has no magnetic field discernible at the 21,598-mile approach of - Mariner II and at that altitude there were no regions of trapped - high-energy particles or radiation belts, as there are near the Earth. - -—The clouds of Venus are about 15 miles thick, extending from a base 45 - miles above the surface to a top altitude of about 60 miles. - -—At the resolution of the Mariner II infrared radiometer, there were no - apparent breaks in the cloud cover. Cloud-top temperature readings are - about minus 30 degrees F near the center (along the terminator), and - ranging down to minus 60 degrees to minus 70 degrees F at the limbs, - showing an apparent limb-darkening effect, which would indicate a hot - surface and the absence of a supercharged ionosphere. - -—A spot 20 degrees F colder than the surrounding area exists along the - terminator in the southern hemisphere: a high mountain could exist in - this region, but such an hypothesis is purely conjectural. A bright - radar reflection is also found on the Equator in the same general - region. Causes of these phenomena are not established. - -—At their base, the clouds are about 200 degrees F and probably are - comprised of condensed hydrocarbons held in oily suspension. Below the - clouds, the atmosphere must be heavily charged with carbon dioxide, - may contain slight traces of oxygen, and probably has a strong - concentration of nitrogen. - -—112 - -—As determined by the microwave radiometer, Venus’ surface temperature - averages approximately 800 degrees F on both light and dark sides of - the planet. Some roughness is indicated and the surface reflectivity - is equivalent to that of dust and sand. No water could be present at - the surface but there is some possibility of small lakes of molten - metal of one type or another. - -—Some reddish sunlight, in the filterable infrared spectrum, may find - its way through the 15-mile-thick cloud cover, but the surface is - probably very bleak. - -—The heavy, dense atmosphere creates a surface pressure of some twenty - times that found on the Earth, or equal to about 600 inches of - mercury. - - -The mission was completed and the spacecraft had gone into an endless -orbit around the Sun. But before Mariner II lost its sing-song voice, it -produced 13 million data words of computer space lyrics to accompany the -music of the spheres. - - - - - APPENDIX - SUBCONTRACTORS - - -Thirty-four subcontractors to JPL provided instruments and other -hardware for Mariners I and II. - -The subcontractors were: - - Aeroflex Corporation Jet vane actuators - Long Island City, New York - American Electronics, Inc. Transformer-rectifiers for flight - Fullerton, California telecommunications - Ampex Corporation Tape recorders for ground telemetry - Instrumentation Division and data handling equipment - Redwood City, California - Applied Development Corporation Decommutators and teletype encoders - Monterey Park, California for ground telemetry equipment - Astrodata, Inc. Time code translators, time code - Anaheim, California generators, and spacecraft signal - simulators for ground telemetry - equipment - Barnes Engineering Company Infrared radiometers - Stamford, Connecticut Planet simulator - Bell Aerospace Corporation Accelerometers and associated - Bell Aerosystems Division electronic modules - Cleveland, Ohio - Computer Control Company, Inc. Data conditioning systems - Framingham, Massachusetts - Conax Corporation Midcourse propulsion explosive - Buffalo, New York valves - Squibs - Consolidated Electrodynamics Corp. Oscillographs for data reduction - Pasadena, California - Consolidated Systems Corporation Scientific instruments - Monrovia, California Operational support equipment - Dynamics Instrumentation Company Isolation amplifiers for telemetry - Monterey Park, California Operational support equipment - Electric Storage Battery Company Spacecraft batteries - Missile Battery Division - Raleigh, North Carolina - Electro-Optical Systems, Inc. Spacecraft power conversion - Pasadena, California equipment - Fargo Rubber Corporation Midcourse propulsion fuel tank - Los Angeles, California bladders - Glentronics, Inc. Power supplies for data - Glendora, California conditioning system - Groen Associates Actuators for solar panels - Sun Valley, California - Houston Fearless Corporation Pin pullers - Torrance, California - Kearfott Division Gyroscopes - General Precision, Inc. - Los Angeles, California - Marshall Laboratories Magnetometers and associated - Torrance, California operational support equipment - Matrix Research and Development Power supplies for particle flux - Corporation detectors - Nashua, New Hampshire - Menasco Manufacturing Company Midcourse propulsion fuel tanks and - Burbank, California nitrogen tanks - Midwestern Instruments Oscillographs for data reduction - Tulsa, Oklahoma - Mincom Division Tape recorders for ground telemetry - Minnesota Mining & Manufacturing and data handling equipment - Los Angeles, California - Motorola, Inc. Spacecraft command subsystems, - Military Electronics Division transponders, and associated - Scottsdale, Arizona operational support equipment - Nortronics Attitude control gyro electronic, - Division of Northrop Corporation autopilot electronic, and antenna - Palos Verdes Estates, California servo electronic modules, - long-range Earth sensors and Sun - sensors - Ransom Research Verification and ground command - Division of Wyle Laboratories modulation equipment - San Pedro, California - Rantec Corporation Transponder circulators and monitors - Calabasas, California - Ryan Aeronautical Company Solar panel structures - Aerospace Division - San Diego, California - Spectrolab Solar cells and their installation - Division of Textron Electronics, and electrical connection on - Inc. solar panels - North Hollywood, California - State University of Iowa Calibrated Geiger counters - Iowa City, Iowa - Sterer Engineering & Manufacturing Valves and regulators for midcourse - Company propulsion and attitude control - North Hollywood, California systems - Texas Instruments, Inc. Spacecraft data encoders and - Apparatus Division associated operational support - Dallas, Texas equipment, ground telemetry - demodulators - Trans-Sonic, Inc. Transducers - Burlington, Massachusetts - -In addition to these subcontractors, over 1,000 other industrial firms -contributed to the Mariner Project. - - - - - FOOTNOTES - - -[1]Throughout this book “Mariner” refers to the successful Mariner II - Venus mission. Mariner I was launched earlier but was destroyed when - the launch vehicle flew off course. - -[2]For scientific reasons, distances from Venus are calculated from the - center of the planet. Hereafter in this chapter, these distances - will be reckoned from the surface. - - - - - INDEX - - - A - ABMA, 17 - Agena B, 21, 22, 40 - Antennas, 66 - Goldstone, description, 70, 71, 73 - onboard, description, 30, 31 - directional control, 30 - Pioneer tracking site, 70, 71 - ARPA, 17 - Astronomical unit, 111 - refinement, 107 - Atlantic Missile Range, 2, 10, 43, 83 - Atlas-Agena B, 63, 52 - Atlas D, 19, 21, 36-39, 89 - Attitude control - Atlas D, 38 - Earth acquisition, 58 - loss of control and reorientation, 56, 60 - Attitude control system, 31, 32 - - - B - Battery, 25, 27 - Bumper-WAC, 18 - - - C - C-133 aircraft, 43 - Centaur, 8 - Central Computer and Sequencer, 28 - commands, 56, 58 - failure at encounter, 62 - midcourse maneuver control, 59 - Central Computing Facility, 81, 82 - Charged particles, 13, 90 - Charged particle detector, 35, 88 - Computers, data processing, 84 - Corporal E, 18 - Cosmic dust, 13 - density, 110 - distribution and mass, 94, 95 - measurement, 89 - Cosmic dust detector, 35, 68, 87, 89 - Cosmic radiation, 13, 96 - Cosmic ray flux, 98 - - - D - Data conditioning system, 88 - Data processing, 30, 74, 85 - CCF, equipment and operation, 82, 83 - launch and tracking operations, 83 - telemetry data, 84 - transmission time, 88 - Detectors - charged particle, 35 - cosmic dust, 35 - solar plasma, 35 - DSIF, 73, 74, 75, 82, 83, 84 - functions, 68 - Goldstone, 1, 64, 67-79, 68, 69, 70, 71, 73, 75, 84, 107, 108, - 109 - Johannesburg, 64, 67, 68, 73 - Mobile, 68, 73, 80 - tracking during midcourse maneuver, 56 - orientation, 56 - Woomera, 67, 68, 71, 73, 75 - - - E - Earth sensor - final orientation commands, 64 - September 8, crises and recovery, 60 - Echo Project, 69 - Echo site functions, 71 - Electronics equipment weight, 25 - Explorer I, 19 - Experiments, 35 - Anton special purpose tube, 87 - atmospheric investigation, 85 - charged particle detector, 88, 96-100 - density variation data, 98 - radiation hazard findings, 98 - cosmic dust detector data, 87-89, 94, 95 - high energy radiation, 90 - infrared radiometer, 87, 93 - ion chamber and Geiger-Mueller tubes, 87 - magnetometers, 87, 88 - microwave radiometer, 87, 91-93 - objectives, 13, 93 - processing of data, 85 - radiometers, 85, 105, 106 - responsible organizations, 88 - results, 110-112 - solar plasma detector, 87-90 - temperature investigation, 85 - transmission of data, 88 - weight, 25 - - - G - Geiger counter, 98 - Geiger-Mueller tubes, 87, 91 - George C. Marshall Space Flight Center, 13, 17 - Goldstone Tracking Station, 64, 67, 69, 75, 84, 107 - Echo site, 68, 69, 71, 73 - Pioneer site, 56, 68, 70 - Venus site, 69, 70, 108, 109 - Guidance, 13 - - - H - High-energy radiation experiments, 90, 91 - - - I - Infrared radiometer experiment - cloud observations, 103, 105, 106 - description, 93 - dimensions, 93 - operating characteristics, 85, 93 - Interplanetary magnetic field, 13, 99 - Interplanetary space - cosmic dust density, 110 - distribution, 95 - hazards to spacecraft, 13 - Ion chamber, 98 - - - J - Johannesburg tracking station, 67, 68 - equipment, 68, 73 - functions, 68, 73 - JPL, 2, 8, 13, 75, 76, 80, 82, 84 - accomplishments, 18, 19 - background, 18 - DSIF control point, 67, 68 - pre-Mariner spacecraft, 23 - Jupiter, contrast to Venus, 101 - Jupiter C, 19 - - - L - Launch Operations Center, 12, 17 - Launching, 56 - Atlas performance, 52, 53 - Atlas-Agena B, 52 - battery, 52 - gyroscopes, 53 - radio guidance system, 52 - time limitations, 12 - - - M - Magnetometer experiment, 35, 88 - data, 101, 102 - description, 91 - function, 91 - objectives, 100 - onboard location, 91 - Mariner I, 43-45 - Mariner R, 41 - Masers, 70 - Materials, thermal shielding, 33 - Microwave radiometer experiment - description, 91 - function, 91 - measurements, 103, 105 - operating characteristics, 85, 92-93 - Midcourse maneuver, 32, 58-59, 60, 65 - Mission achievements, records, 65 - Mobile tracking station, 68, 80 - location, equipment and function, 73 - MX-774 Project, 21 - - - N - NACA, precursor of NASA, 16 - NASA, 8, 16, 17 - - - P - Parking orbit, 55 - Pioneer III, 19 - Pioneer IV, 19 - Pioneer project, 69 - Pioneer tracking site, 70, 71 - Power system, 25 - Private A, 18 - Propellants - Atlas D, 38 - attitude control system, 32 - spacecraft, controlled burning, 32 - rocket thrust system, 32 - Propulsion system, Mariner - spacecraft, hydrazine propellant, 33 - propellant storage, 32, 38 - weight, 25 - - - R - Radiation, 98-100 - Ranger III, 8 - Receivers, 66 - Records, Mariner - attitude control system, 65 - measurements near Sun, 65 - operation near Venus - telemetry measurements, distance, 65 - trajectory correction maneuver, 65 - transmission, continuous performance, 65 - - - S - Sensors - Earth, for attitude control, 32 - Sun, for attitude control, 32 - Sergeant missile, 19 - Shielding, 33, 34 - Solar cells, 27, 28 - Solar flares, 98, 99 - Solar panels - description, 25 - design, 27 - output deterioration, 61 - release, 11 - support, 25 - weight, 27 - Solar plasma detector, 35, 88, 96, 97 - description, 87, 89, 90 - function, 87, 89, 90 - recordings, 96, 97 - Solar plasma flux - correlation with geomagnetic effects, 97 - Solar wind - effects on cosmic-ray movements, 96 - magnetic fields, 95, 96 - low density and energy, 96 - measurement, 89 - particle concentration near Earth, 96 - particle energies, 96 - temperature, 96 - theories, 95 - velocities, 13, 95, 96, 97, 110 - Space Flight Operations Center, 60 - organization and operation, 75, 80, 81 - Space simulator, temperature control, 41 - Spacecraft, 31 - attitude control system, 31 - Central Computer and Sequencer, 28 - components and subsystems, 27 - configuration, 23 - electronic equipment, 25 - frame materials, 23, 25 - launching, 12 - power system, 25 - preliminary design, 41 - propulsion system, 32 - shroud and adapter, 43 - system tests, 41 - telecommunications subsystem, 30 - temperature, 33 - test models, 41 - testing, 23 - trajectory, 11 - weight, 25 - Sun sensor, 32 - - - T - Telemetry - continuous transmission, 65 - data processing, 84 - description, 30 - loss of monitoring data, 62 - phase-shift modulation, 30 - transmission cutoff, 64 - Telemetry processing station, 82, 83 - Telemetry system - data processing, 30 - onboard, description, 30 - Temperature control - coatings, 34 - heating problems, 62 - housing structures, 35 - materials, 33 - problems, 33 - solar panels, 35 - solar radiation shielding, 35 - thermal shielding, 33 - Tracking - Antigua, 53 - Ascension, 53, 55 - DSIF, 52, 66, 67, 68, 69 - Earth noise, 66 - Grand Bahama Island, 53 - Johannesburg, 56 - Pretoria, 53, 55 - problems, 66 - radio noise, 66 - San Salvador, 53 - solar noise, 66 - Twin Falls Victory, 53, 55 - Whiskey, 55 - Woomera, 56 - Trajectory, 11, 63, 64, 83 - - - V - V-2 rocket, 18 - Van Allen radiation belt, 19, 97 - Venus - atmosphere, 3, 5, 104, 105, 112 - atmospheric temperature, 85 - atmospheric winds, 5 - CO₂ content above clouds, 106 - cloud cover, 105, 106 - cloud observations, 104, 105 - clouds, data, 111 - compared with Earth, 5 - description, 4 - dielectric constant, surface material, 107 - encounter, 93, 94 - historical data, 2 - inferior and superior conjunctions, 4 - magnetic field, 98, 100, 111 - comparison with geomagnetic, 100, 101 - data, 100, 101, 102 - strength, 100, 101, 102 - mass, 109, 111 - orbit, 4 - radar experiments, 1961, 106, 107 - radar experiments during mission, 107 - reflection coefficient, 107 - revolution, 4 - rotation, 4, 101, 108, 111 - surface, 106 - brightness temperature, 103, 104 - characteristics, theories, 102, 103 - “greenhouse” effect, 106 - measurements, 103, 104 - pressure, 112 - reflectivity, 111 - roughness, 107, 108 - temperature, 106, 111 - temperature, 85, 111 - topography, 5 - water vapor in atmosphere, 106 - Venus encounter, 63 - - - W - WAC Corporal, 18 - Woomera Tracking Station, 67, 68, 75 - equipment, 68, 71, 73 - - - - - Transcriber’s Notes - - -—Retained publication information from the printed edition: this eBook - is public-domain in the country of publication. - -—In the text versions only, text in italics is delimited by - _underscores_. - -—Silently corrected a few typos. - -—In the index, entry “propellant storage”, replaced one nonsensical page - number (200) with a plausible conjecture (38). - - - - - - - -End of the Project Gutenberg EBook of Mariner Mission to Venus, by -Jet Propulsion Laboratory - -*** END OF THIS PROJECT GUTENBERG EBOOK MARINER MISSION TO VENUS *** - -***** This file should be named 54585-0.txt or 54585-0.zip ***** -This and all associated files of various formats will be found in: - 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