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.

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.

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.

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.

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.

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.

Final NACA meeting, August 21, 1958.

Model of X-1 research plane.

Headquarters of National Aeronautics and Space Administration, Washington, D.C.

JPL developed first JATO units in 1941.

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.

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.

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:

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.

This hexagonal frame, constructed of magnesium and aluminum, is the basic supporting structure around which the Mariner spacecraft is assembled.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Two assembly operations and system checkouts are performed separated by a trip to the pad to verify compatibility with the launch vehicle

A complete electronic checkout station in the hangar supports the spacecraft to ensure operability

Mariner takes form as the solar panels are attached and the final hangar checkout operations are performed before the launch.

Wrapped in a dust cover, the spacecraft is transferred from Hangar AE at AMR to the explosive safe area for further tests.

Inside the bunker-like explosive safe area, the powerful midcourse maneuver rocket engine is installed in the center of the spacecraft.

Final assembly and inspection complete, Mariner is “canned” in the nose shroud that will protect it through the Earth’s atmosphere and into space.

At the pad, the shrouded spacecraft is lifted past the Atlas ...