[127] The second decade of space exploration by the U.S. began and ended with a presidential reaffirmation of interest in the space program. But space science was not high on Presidents Richard M. Nixon's and Jimmy Carter's list of space objectives. President Nixon established a Space Task Group in 1969 to provide him with near-future recommendations "on the direction the U.S. space program should take in the post-Apollo period."* The task group's final proposal emphasized space applications and national defense. There would be no expensive "space spectaculars" during the 1970s equivalent to the Apollo manned lunar landings. NASA was urged to build on the knowledge and experience of its first 10 years to develop a stronger program of practical applications satellites that would deliver a speedy return on the taxpayers' space dollars and "improve the quality of life on Earth." Task group members recommended that NASA pursue the development of remote sensing, communications, and meteorology satellites. It was left to the Department of Defense to use space "non-provocatively" to enhance national security.1

Nixon's advisers did not ignore space science. They directed the civilian agency to expand man's understanding of the universe with a "strong program of lunar and planetary exploration, astronomy, physics, the earth and life sciences." However, this healthy program had to be accomplished on a bare-bones budget. NASA's scientists had hoped for more fiscal support from Congress and the White House during the 1970s; nevertheless, the agency succeeded in bringing to fruition a respectable program of scientific exploration. Long-time leader of NASA's space science program Homer E. Newell wrote that space science during the second decade "returned a considerable momentum, with the prospect of challenging and important problems to work on for the foreseeable future."2 While Carter's space policy statements in 1978 highlighted the development and use of the Space Shuttle and space applications projects, the president also wished to "emphasize space science and exploration in a manner that retains the challenge and excitement and permits the nation to retain the vitality of its space technology base"-as long as it could be done at a [128] reasonable cost.3 NASA built on its experiences of the 1960s with earth orbital satellites and interplanetary probes to accomplish even more sophisticated scientific tasks near earth and on other planets during the 1970s, an accomplishment that NASA's managers hoped would renew the nation's interest in space science for the 1980s.


The First Decade Reviewed

The National Aeronautics and Space Act of July 1958, which established NASA, directed the new agency to expand the body "of human knowledge of phenomena in the atmosphere and space." NASA accomplished this directive by embracing a disparate group of scientists, managers, and propulsion experts from several organizations, namely one branch of the Naval Research Laboratory, the California Institute of Technology's Jet Propulsion Laboratory, which was engaged in work for the Army, and the National Advisory Committee for Aeronautics (NACA). These three groups of individuals became the nucleus of three NASA centers of research - the Goddard Space Flight Center, the Jet Propulsion Laboratory, and the Langley Research Center - retaining their uniqueness and individuality but working as a team to explore the new frontier offered them by rocket propulsion.

Managers at NASA Headquarters organized space science into several disciplines, the major ones being physics and astronomy, lunar and planetary exploration, and life sciences. These three broad programs included the fields of geodesy, atmospheric and ionospheric physics, magnetospheric research, lunar and planetary science, solar studies, galactic astronomy, and bioscience. To this list were added comparative planetology, exobiology, and high-energy astronomy during the 1970s.

By necessity, NASA's first scientific satellites were small instrumented packages. Vanguard and Explorer satellites were sent to sample the near-earth environment. As launch vehicles became more accurate and powerful, scientists were able to increase the size and weight of their experiments and send them to higher orbits and to the vicinity of the moon and the near planets. The Explorer, Orbiting Solar Observatory, Orbiting Astronomical Observatory, Orbiting Geophysical Observatory, and Biosatellite programs returned valuable data from earth orbit, while Pioneer, Ranger, Lunar Orbiter, Surveyor, and Mariner gave investigators their first in situ measurements of the world beyond. The U.S. shared its expertise and its launch vehicles with other countries in its attempt to explore and understand the regions beyond earth's obscuring atmosphere. The next decade would see a continuation of these successful programs.


Space Science, 1969-1978

The physics and astronomy program sponsored 17 Explorer satellites, 3 High Energy Astronomy Observatories, 2 Orbiting Astronomical Observatories, 1 Orbiting Geophysical Observatory, and 4 Orbiting Solar Observatories (see table 3-1).

[129] As presented in the tables in this chapter, these satellites were designed to achieve a wide variety of scientific goals. A typical Explorer, of which there were 8 distinct classes, was sent to earth orbit to obtain measurements of the meteoroid penetration rate, or to collect particles and field data, or to pursue any number of related experiments. Studying x-rays and gamma rays was the assignment given the High Energy Astronomy Observatories. The Orbiting Solar Observatories sent back high-resolution data from the sun.

The bioscience program supported only one satellite, Biosatellite 3, but a large portion of the experiments accomplished on board the Skylab orbital workshop by nine astronauts was designed by NASA's life scientists. Exobiologists searching for life forms on other planets and looking for clues to the genesis of life on earth sent their first experiments to another planet in 1976 aboard two Mars-bound Viking spacecraft.

Mariner and Viking's spectacular images of the Red Planet were not the only significant "pictures" received from elsewhere in the solar system. Pioneer and Voyager returned great quantities of new information from the vicinity of Venus, Jupiter, and Saturn.


Managing the Space Science Program at NASA

From November 1963 until December 1971, space science and space applications were managed as one program at NASA Headquarters. The two were divided in an agency-wide reorganization by Administrator James C. Fletcher. John E. Naugle assumed the reins of the space science program from Homer Newell in later 1967 and continued to lead the program until 1974, when Noel W. Hinners was named associate administrator.

Planetary investigations were led by three men during the decade: Donald P. Hearth (1969-1971), Robert S. Kraemer (1972-1976), and A. Thomas Young (1977-1978). Physics and astronomy programs were supervised by Jesse Mitchell (1969-1973), Alois W. Schardt (1974-1976), and T. B. Norris (1977-1978). Bioscience was under the direction of Orr E. Reynolds until 1971, when the program was reorganized under the Office of Manned Space Flight. David Winter was directing the effort when the discipline was moved back to the Office of Space Science in 1976. The vehicles used to launch space science payloads were managed at headquarters by Joseph B. Mahon until 1976, when they became the responsibility of the....



[130] .....new Office of Space Flight. For more details on the management of NASA's Office of Space, see table 3-2.

The lead centers involved in the space science program included the Jet Propulsion Laboratory, Ames Research Center, Goddard Space Flight Center, and Langley Research Center.



[133] BUDGET

For a general introduction to the NASA budget process and to the budget tables in this volume, consult chapter 1. Other data that may assist the researcher interested in the cost of NASA's space science program include budget tables in chapter 1 for the various launch vehicles used by the Office of Space Science in 1976-1978. Chapter 6 provides budget data on the tracking network that supported the agency's space science flight projects. For a more detailed breakdown of the flight project budgets, see the NASA annual budget estimates referred to in chapter 1. Review the bottom notes of all tables carefully before making conclusions about totals for any particular project or year.


Money for Space Science

NASA's overall budget declined almost yearly during the agency's second decade (6 out of 10 years, with appropriations ranging from $4.1 billion in 1978 to $3 billion in 1974), and the civilian agency never regained during its second 10 years the generous $5 + billion budgets it enjoyed during the mid-1960s. The number of dollars for space science, however, increased during the post-Apollo years. The average annual budget for space science in the 1960s was $384.9 million; during the 1970s it was $550.5 million. But the increase was offset by inflation and rising costs. The average annual space science budget was a slightly smaller percentage of the total NASA budget during the second 10 years. The average percentage of the total NASA appropriation alloted for space science in 1959-1968 was 17.6%; it was 17% in 1969-1978.

Table 3-3 summarizes the space science funding history, and table 3-4 breaks....



[133] .....down costs per program. The remaining budget tables give the researcher totals by discipline and flight project.




Space science projects during the 1970s fell into one of three broad programs: physics and astronomy, lunar and planetary science, or life sciences. Each program is discussed in the following pages. Individual flight projects are highlighted within the appropriate program.



NASA's space science efforts were largely divided between two categories: physics and astronomy or lunar and planetary. The agency launched 53 payloads that were dedicated to the physics and astronomy program during NASA's second decade of operations. Specialists working in such fields as astronomy, solar physics, particles and fields, and ionospheric physics contributed to man's knowledge of earth, the near-earth environment, and earth's relationship with its sun. They did so by sending their instruments above earth's obscuring atmosphere on board a variety of satellites.4

Explorer and Explorer-class satellites provided investigators with 42 opportunities for investigations. For the several kinds of Explorers, scientists designed experiments that could record data on gamma rays, x-rays, energetic particles, the solar wind, meteoroids, radio signals from celestial sources, solar ultraviolet radiation, and other phenomena. Many of the Explorer-class missions were joint endeavors conducted by NASA and other countries, part of the agency's international program.

Four observatory-class spacecraft provided flexible orbiting platforms for scientific experiments. The last of the Orbiting Geophysical Observatories (OGO 6), NASA's first multiuse "streetcar" satellite design that could accommodate a variety of instruments, performed its mission in 1969. OGO participants studied data gathered on atmospheric composition.

[152] One Orbiting Astronomical Observatory (OA0 3) sent eight years' worth of information on the composition, density, and physical state of matter in interstellar space.

High-quality data on x-ray, gamma ray, and cosmic ray sources were the rewards returned by three High Energy Astronomy Observatories. HEAO was NASA's most expensive physics and astronomy project of the 1970s and one of its most productive.

The Orbiting Solar Observatory series, begun in the 1960s, took on a new look with OSO 8. After the launch of three more OSO spacecraft of the original design, NASA orbited a much larger satellite created to investigate the sun's lower corona, the chromosphere, and their interface in the ultraviolet spectral region.

The following sections describe these four programs and provide mission details for each mission.

Jesse Mitchell, who became director for the physics and astronomy program in 1966, stayed in this post until 1973, when Alois W. Schardt succeeded him. In 1976, T. B. Norris took over the post and saw the program through the rest of the agency's second decade. At NASA Headquarters, program managers for each of the major flight programs reported to the director, as did chiefs for such disciplines as solar physics, magnetospheric physics, and astronomy. The major centers contributing to physics and astronomy projects were the Goddard Space Flight Center and Marshall Space Flight Center.



"Explorer," as the name of a scientific satellite, had many meanings. The original Explorer program predated NASA, with the launch of the Army Ballistic Missile Agency's small torpedo-shaped Explorer I taking place on January 31, 1958. The civilian space agency inherited the Army's Explorer program and adopted the name to refer to its several series of simple, small, and relatively inexpensive satellites used to further physics and astronomy investigations. During its first decade, NASA successfully launched 35 satellites bearing the Explorer name to perform a variety of data-gathering tasks. Additionally, the U.S. assisted other countries with the building and launching of other Explorer-class spacecraft with designations like Alouette, San Marco, and ESRO.

NASA's space scientists involved in solar-terrestrial and astrophysics research continued to use the Explorer program during the 1970s. Table 3-54 summarizes the various Explorer missions; tables 55-70 provide details on each specific flight.

Three atmospheric Explorers (Explorer 51, 54, and 55) sought temperature, composition, density, and pressure data to permit the study of the physics of the atmosphere on a global basis. Researchers were particularly interested in studying the relationship of solar ultraviolet activity to atmospheric composition in the lower thermosphere. Experiments were devised by investigators at more than a dozen institutions for this RCA Astro-Electronics-manufactured satellite. The Goddard Space Flight Center managed the project.

The earth's magnetosphere was the object of study for a large number of Explorer missions, of which there were several distinct types. Explorer 45, made in-house at Goddard, was launched to study the dynamic processes that occur in the inner magnetosphere at distances from two to five earth radii. Explorer 52, the last [153] of the University of Iowa Hawkeye/Injun series, was put into solar orbit to collect data on the interaction of the solar wind with the geomagnetosphere over the polar caps. The last 4 of a series of 10 interplanetary monitoring platform (IMP) Explorers began their work during the second decade of NASA's operations, assisting with the study of interplanetary radiation and magnetic fields within and beyond earth's magnetosphere. Instruments from many scientific institutions were included on the payloads of Goddard's Explorer 41, 43, 47, and 50.

NASA's Wallops Station and the Naval Research Laboratory worked together to instrument and launch Explorer 44, a solar physics investigation. The spacecraft was designed to monitor the solar flux in a number of wavelength bands, with special emphasis on the ultraviolet region of the spectrum.

Johns Hopkins Applied Physics Laboratory joined with Goddard to develop two x-ray astronomy Explorers. Explorer 42 and 53 carried instruments to earth orbit to study celestial x-ray sources. Explorer 48, a Goddard-built spacecraft, sought galactic and extragalactic gamma ray point sources. A Delta launch vehicle placed Explorer 49 in orbit about the moon so that it could measure the intensity of radio signals from celestial sources. Radio astronomers at Goddard were rewarded by data on cosmic background noises, solar radio burst phenomena, and radio emissions from earth.

For international satellite projects of the Explorer class, see this chapter under "Other Physics and Astronomy Projects."



High Energy Astronomy Observatory

The primary objective of the High Energy Astronomy Observatory (HEAO) program was to obtain high-quality, high-resolution data on x-ray, gamma ray, and cosmic ray sources. Experiments were designed to provide data on the structure, spectra, polarization, synoptic variations, and location of these sources. HEAO was NASA's primary physics and astronomy project planned for the 1970s.

NASA had begun its search for information on celestial energy sources during its first decade, using Explorer satellites to gather data on cosmic radiation. Explorer 11 (1961) was the first astronomical satellite designed to detect high-energy gamma rays. The Small Astronomy Satellite series (Explorer 42, 48, and 53) was launched during the 1970s to return data on x-ray, gamma ray, and ultraviolet sources. Explorer 42, also called Uhuru, was the first satellite completely dedicated to x-ray astronomy. In the late 1960s during early discussions of a large satellite project dedicated to high-energy astronomy observations, some participants labeled it a "Super Explorer."5

As originally conceived, HEAO was a much larger satellite than any of the Explorers. The two cylindrical HEAO satellites would weigh 9700 kilograms (the heaviest Explorer of the 1970s was 675 kilograms) and measure 11.5 x 3 meters. With 13 000 kilograms of experiments aboard, HEAO would be launched by a Titan IIIC, D, or E. Additionally, advanced planners were working on two follow-on [165] missions. In 1969, NASA Headquarters assigned the management of HEAO to the Marshall Space Flight Center in Huntsville, Alabama.**

With the initial design studies completed in-house, MSFC issued its first request for proposals (RFP) for a preliminary design study of HEAO in February 1970 and held a briefing for scientists and instrument builders in April. MSFC announced in May that Grumman Aerospace Corporation and TRW, Inc., would work under separate contracts to define the observatory further. While the two contractors performed their tasks, NASA scientists reviewed the 55 proposals they had received for HEAO experiments, choosing 7 experiments for HEAO-A and 5 with I reserve for HEAO-B in late 1970. In April 1971, TRW and Grumman had completed their studies and were preparing their bids for the final development and fabrication contract, which was won by TRW late in the year. The contract called for system engineering of the payload, design and development of the spacecraft, procurement and integration of the orbit adjust stage and shroud, experiments integration, design, development, and delivery of one set of ground support equipment, launch operations support, and mission operations support for up to two years after launch. With the endorsement of the National Academy of Sciences, NASA and its contractors were proceeding toward their first 1975 launch deadline when a budget cut by Congress in January 1973 forced them to halt their plans for at least a year while Headquarters officials looked for ways to reduce its science program by at least $95 million.

HEAO was redefined. The two large observers were replaced by three smaller satellites able to carry 3000 kilograms of experiments (see fig. 3-1). The agency was forced to drop some of the original experiment proposals, but directed the investigators to resize their hardware where possible. New requirements for modular experiment packages rather than a single integrated experiment system would also save money. NASA retained TRW as its prime spacecraft contractor, who reported that approximately 80% of the systems planned for HEAO had been flown on previous satellites, which would translate into additional money saved. Atlas-Centaur replaced Titan as the launch vehicle for the missions, which were postponed until 1977-1979.

HEAO-A was dedicated to scanning x-ray experiments; HEAO-B, which would require additional attitude positioning equipment, would carry a pointing x-ray telescope; and HEAO-C would scan for gamma and cosmic rays. The objective of the x-ray studies was a survey of the sky for x-ray sources down to about 10-6 times the intensity of the brightest known source and to investigate the shape and structure of x-ray sources with high-resolution instruments. Gamma ray observations would concentrate on a broad survey of the sky and on high-resolution studies of individual sources. Primary cosmic rays investigations would require large detector areas and long observing times so that a survey of cosmic ray particulates with statistically meaningful numbers could be obtained.



Figure 3-1. HEA0 High Energy Astronomy Observatory.

Figure 3-1. HEA0 High Energy Astronomy Observatory.



Tables 3-72, 73, and 74 list the individual experiments conducted by the three observatories (four for HEA0 1, five for HEA0 2, and three for HEA0 3) and the organizations that served as contractors. The California Institute of Technology, Washington University, the University of Minnesota, MIT, the University of California at San Diego, the Naval Research Laboratory, Columbia University, and the Goddard Space Flight Center were among the original experiment proposers.

Atlas-Centaur vehicles launched all three HEAO satellites successfully into low-earth orbits. Scheduled for six months of operations, HEAO 1, launched in August 1977, exhausted its supply of control gas in January 1979. Placed in orbit in November 1978, HEA0 2- an orbiting pointing x-ray telescope - operated with a high rate of success for 30 months. HEA0 3, launched in September 1979, returned data for 20 months.

F. A. Speer was project manager at Marshall, with R. E. Halpern serving as program manager at NASA Headquarters. The Goddard Space Flight Center served as the mission operations center for HEAO. Table 3-71 provides a chronology of HEAO's development and operations.



Orbiting Astronomical Observatory

The Orbiting Astronomical Observatory (OAO), part of the physics and astronomy program, was established at NASA in 1959 (see vol. 2, table 3-110 for a chronology of development and operations). Astronomers required stable orbiting platforms with telescopes to make observations in the infrared, optical, ultraviolet, and x-ray regions of the spectrum beyond earth's obscuring atmosphere. The Grumman-manufactured OAO spacecraft, basically a hollow cylindrical tube in which experiments were housed, could be precisely pointed with an accuracy of 1 minute of arc.

Two of the four planned OAO missions were launched in 1966 and 1968 with mixed results. OAO I suffered a battery malfunction and failed 1.5 hours into the mission. OAO 2 performed better than its designers had expected, returning useful data on the celestial sphere until February 1973. The third mission (OAO-B) failed when the protective nose cone failed to jettison during a launch attempt in 1970. The satellite never reached orbit. OAO 3, also called Copernicus, was highly successful, returning data from 1972 until 1980.

The experiments gathered for the unsuccessful OAO-B were called the Goddard Experiments Package, after rocket pioneer Robert Goddard. The investigators had planned to gather high-resolution spectral data from pointed and extended sources in the ultraviolet region of the spectrum. There were seven detectors in the Goddard [171] package: six for ultraviolet and one for visible light (see table 3-75). OAO-B's spectrophotometer was a 38-inch Cassegrain telescope with a Wright-Smith spectrometer; its spectral range was 1100-4267 Angstrom, with a resolution of 2A-8A-64A and a pointing accuracy requirement of 1 arc second.6

The highly successful OA0 3 returned data for eight years on the birth, death, and life cycles of stars. Its 450-kilogram Princeton Experiments Package contained a 32-inch telescope and spectrometer with a spectral range of 80-3000 Angstrom, a resolution of 0.1-0.5 Å, and a pointing accuracy requirement of 0.1 arc second. OAO 3 could view stars to the sixth magnitude. An x-ray experiment sponsored by University College of London studied stellar x-ray sources and x-ray absorption in interstellar space with three small telescopes (see table 3-76).7

The Orbiting Astronomical Observatory program was managed at NASA Headquarters by C. Dixon Ashworth. The Goddard Space Flight Center directed the project under the leadership of J. Purcell, OAO project manager, and J. R. Kupperian, Jr., OAO project scientist.



Orbiting Geophysical Observatories

The Goddard Space Flight Center initiated the Orbiting Geophysical Observatory (OGO) program in 1960. The six TRW-made satellites were designed to carry a large number of measuring instruments to gather data on atmospheric composition, solar emissions, radio astronomy, and other phenomena. OGO was the first scientific satellite designed to perform a variety of roles; instead of being a tailor-made one-instrument package it was a truly automated orbiting laboratory.

Five of the six OGOs were launched during 1964-1968, with OGO 6 being orbited in 1969. Despite attitude control problems, the first five spacecraft in the series sent back over a million hours of data to scientists studying earth-sun relationships (see vol. 2). OGO 6 scientists from over a dozen institutions studied atmospheric phenomena during a period of maximum solar activity (see table 3-77).8


Orbiting Solar Observatories

In 1959, NASA scientists at Goddard Space Flight Center and Headquarters began planning for a series of spacecraft with pointing controls that could be used to take measurements of the sun. Less than three years later, the agency launched the first Orbiting Solar Observatory (OSO), a two-section spacecraft manufactured by Ball Brothers that could accommodate a variety of scientific instruments. The lower...



...wheel-like compartment of OSO was divided into nine compartments, five of which could house instruments, and a sail-shaped upper section for the solar array and instruments that required a fixed solar orientation. During NASA's first decade, the Eastern Test Range saw four successful OSO launches (see vol. 2).

OSO 5 and 6, configured very much like the first four of the series, took their place in orbit in 1969, returning high-spectral resolution data for several years (see tables 3-79 and 80). OSO 7, launched in September 1971, represented an improved design. All the OSO spacecraft were three-gimballed bodies; their wheels spun to provide gyroscopic stabilization and to accommodate the scanning scientific instruments. The earlier OSOs depended on deployable ballast arms; OSO 7 sported a [174] mechanically simplified fixed-ballast system and was twice as heavy as its predecessors -and carried twice as much experiment payload weight. Ball Brothers enlarged the wheel and increased the solar array so that it provided more power (an increase from 30 to 97 watts). Controllers could point OSO 7 at regions of special interest by feeding offset point commands and scan patterns into its biaxial pointing servos (see table 3-81 and figure 3-2).


Figure 3-2. OSO Design Evolution.

Figure 3-2. OSO Design Evolution.

Source: W. H. Follett, L. T. Ostwald, J. 0. Simpson, et al, "A Decade of Improvements to Orbiting Solar Observatories," n.d., p. 1, NASA (Hq.) History Office.


[175] Even before the second OSO mission was completed, investigators began urging NASA to consider an advanced OSO that would allow them to make long-duration measurements of ultraviolet spectral line profiles and obtain pressure and density data in the solar atmosphere. In January 1969, NASA Headquarters approved three follow-on OSO missions if it could get funding from Congress. According to proposals, the new spacecraft would be triple the weight of the original OSO, with 2.5 times the power, increased data rates, and improved pointing accuracy. They would provide scientists an opportunity to study the sun during its quiet period. Congress authorized FY 1970 funds for OSO I, J, and K.

OSO-1 would study energy transfer from the photosphere to the higher levels of the solar atmosphere under quiet sun conditions. OSO J would return data on solar-terrestrial relationships. OSO K would allow the study of heat and particle radiation flow.

In the spring of 1970, NASA's Goddard Space Flight Center issued a request for proposals to industry for a contractor for the new OSO. In addition to Ball Brothers, who made the original solar observatory series, Hughes Aircraft and TRW submitted proposals for this new class of spacecraft. Goddard called for a larger main body with a three-part sail. The 1052-kilogram OSO-1 would require a Delta launcher with strap-on boosters. NASA finalized an OSO contract with Hughes in May 1971. Seven experiment teams were already at work on the payload for the first new observatory.

OSO 8, which was launched in June 1975 after several delays for budget reasons, carried an international experiment package. To provide significant advances in spatial and spectral resolution, two teams provided high-resolution ultraviolet spectrometers: Centre National de la Recherche Scientifique of France and the University of Colorado. The two ultraviolet instruments and six other experiments performed successfully until September 1978 when the satellite was turned off (see table 3-82). OSO-J and -K fell victim to budget cuts that began in 1972 (see table 3-78 for details). OSO 8 was the last of a productive series.9

C. Dixon Ashworth managed the Orbiting Solar Observatory program at NASA Headquarters. At Goddard, J. M. Thole served as project manager for OSO 5, 6, and 7, while Robert H. Pickard took over for OSO 8.




Other Physics and Astronomy Projects

In addition to its own Explorer program and the several orbiting observatory programs discussed above, NASA participated in other Explorer-class physics and astronomy projects, often with foreign countries. NASA's role varied from launch vehicle provider to scientific partner.

From 1969 through 1978, NASA played a role in 28 small scientific satellite launchings, 24 of which were cosponsored by other countries or by the European Space Agency (formerly the European Space and Research Organization). These satellites contributed to our understanding of solar-terrestrial relationships. Seven were designed to study ionospheric physics; six magnetospheric physics, five solar physics, four astronomy, two atmospheric physics, two aeronomy, one thermal dynamics, and one new spacecraft technology (see table 3-83).

Aeros 1 and 2 and San Marcos 3 and 5 collected temperature, composition, density, and pressure data that allowed scientists to study the earth's atmosphere. Information collected by the principal investigators for Ariel 4, ESRO 4, and ISIS 1 and 2 increased our store of knowledge about ionization in the vicinity of earth. Solar physics data were the goals of Azur, Helios 1 and 2, and Solrad IIA and IIB. Solrad was a Naval Research Laboratory managed project for which the Goddard Space Flight Center provided tracking and data acquisition support. ANS and Ariel 5 were dedicated to x-ray astronomy.

The International Ultraviolet Explorer (IUE) project was a joint enterprise, with participants from NASA and its contractors, the European Space Agency, and the British Science Research Council. IUE 1, launched into geosynchronous orbit in January 1978, allowed hundreds of users at two locations to conduct spectral studies of celestial ultraviolet sources. It was the first satellite totally dedicated to ultraviolet astronomy (table 3-104).

NASA provided the IUE spacecraft, optical and mechanical components of the scientific instruments, the U.S. ground observatory, and the spacecraft control software. ESA contributed the solar arrays IUE I needed as a power source and the European ground observatory in Spain. The British Science Research Council oversaw the development of the spectrograph television cameras and, with the U.S., the image processing software.

The objects of IUE's studies were many: faint stars, hot stars, quasars, comets, gas streams, extragalactic objects, and the interstellar medium. The primary instrument for these studies was a 45-centimeter Ritchey Chretien telescope. Geosynchronous orbit permitted continuous observations and real-time data access by the [180] many observers who worked at the two ground observatories. With the increased observing time, many "visiting observers" could take advantage of the ultraviolet astronomy satellite (fig. 3-3). NASA's Goddard Space Flight Center controlled the spacecraft 16 hours of each day, while the European observatory near Madrid controlled it for 8 hours.

The International Sun-Earth Explorer (ISEE) program was a joint NASA European Space Agency endeavor. Originally called International Magnetosphere Explorers, ISEE was a follow-on to the successful Interplanetary Monitoring Platform (IMP) series of Explorer satellites. Three ISEE spacecraft were designed to study solar-terrestrial relationships, monitor the solar wind, and investigate cosmic and gamma ray bursts (see tables 3-99, 100, and 101).

NASA's Goddard Space Flight Center provided ISEE 1 and 3, while Dornier Systems, working under contract for ESA, built ISEE 2. The first two spacecraft were orbited together by a Thor-Delta 2914 in October 1977 and worked together to provide measurements from the furthest boundaries of the magnetosphere and to .....


Figure 3-3. Two IUE ground observatories, located near Washington, D. C, and Madrid, Spain, were designed to resemble and function as typical ground astronomy observatories.

Figure 3-3. Two IUE ground observatories, located near Washington, D. C, and Madrid, Spain, were designed to resemble and function as typical ground astronomy observatories. With a minimum of training, guest observers could take an active part in the real-time control of the spacecraft and the offline processing of image data. The U.S. Ground Observatory at the Goddard Space Flight Center consisted of the ground station, the Scientific Operations Center, and the Operations Control Center.


[181] .... study the solar wind. ISEE 3, launched in August 1978, was placed at a libration point 1.6 million kilometers from earth, where it returned detailed information on the solar wind and its fluctuations, in addition to data on cosmic rays and gamma ray bursts. All three spacecraft were still performing satisfactorily in the early 1980s, and NASA hoped to use ISEE 3 for comet observations in 1985.

The following tables provide details on these Explorer-class spacecraft, their objectives, and their payloads.



NASA's Office of Planetary Programs of the 1970s inherited an ongoing effort to explore the near planets with Pioneer and Mariner probes. With successful manned exploration of the moon, unmanned lunar spacecraft were not needed, and scientists turned their full attention to planetary exploration. They continued the use of probes to the near planets and added orbiters, a Mars lander, and probes to the outer planets to the program.

NASA conducted three Mariner projects during the 1970s, all of which were proposed during NASA's first decade. Mariner Mars 69 spacecraft flew by Mars; Mariner Mars 71 orbited the Red Planet; and Mariner Mercury-Venus probed those two planets.

Although its large Voyager lander project was cancelled in reply to demands from Congress that NASA trim its budget, the agency proposed an alternative - a Viking orbiter-lander mission to Mars. Viking became the first spacecraft to soft-land and conducted extended mission operations on another planet when they touched down on Mars in 1976. 10

With Pioneer, the space agency extended its search for information to the outer planets of the solar system. Pioneer-Jupiter and Pioneer-Saturn began their long journeys in the early 1970s, reaching Jupiter in 1973 and Saturn in 1979. Data received by the scientific investigators only whetted their appetites for more. Pioneer became the first spacecraft to pass beyond the known planets in 1983. Pioneer Venus spacecraft in 1978 took a close look at this nearby planet with both an orbiter and several impact probes.

NASA sent two Voyager spacecraft to the far planets in 1977. Although a substitute for the more ambitious Grand Tour of the outer planets NASA had hoped to conduct, Voyager results have been impressive. Voyager has returned high-resolution images of the two planets, their moons, and rings and are on their way to Uranus and beyond the solar system.

The NASA Office of Planetary Programs was led by Donald P. Hearth until 1971, when Robert S. Kraemer took that position. A. Thomas Young became director of the office in 1976. In addition to program managers for the several flight projects, the director could count on the expertise of program chiefs for planetary astronomy, planetary atmospheres, planetology, planetary quarantine, and exobiology. Centers involved in planetary exploration projects included the Jet Propulsion Laboratory, Langley Research Center, and Ames Research Center.



NASA initiated the Mariner program in the early 1960s as its key to investigating the nearby planets. These small (200-260-kilogram) spacecraft were designed to fly by our closest neighbors, Mars or Venus, and collect scientific data on the planets' atmosphere and surface. Mariner 2 became the first spacecraft to scan another planet in December 1962, when it passed within 34 762 kilometers of Venus. Mariner 4 provided investigators with the first closeup images of Mars in July 1965. Venus was again the subject of observation when Mariner 5 collected data [203] from 4000 kilometers away in 1967. Proposals for more sophisticated Mariner orbiters and landers were never pursued during the 1960s because of several budget cuts and unforeseen delays with the development of more powerful launch vehicles (see vol. 2).

The three distinct Mariner projects carried out during the 1970s all had been proposed during NASA's first decade. Two of these projects, Mariner Mars 69 and Mariner Mars 71, proved to be critical steps for the Office of Space Science's Viking orbiter-lander mission to the Red Planet (1975-76). Mariner 6 and 7 (Mariner Mars 69) flew by Mars at 3218 kilometers to study the atmosphere and the planet's surface, establishing a basis for future experiments that would search for extraterrestrial life. The two spacecraft also demonstrated engineering concepts and techniques required for long-duration flight away from the sun. Mariner 9 (Mariner Mars 71) was in orbit around Mars for 90 days, providing more than 5000 television images of the surface and data about the planet's composition and atmosphere. Mariner 10 (Mariner Mercury-Venus), another flyby mission, used the gravity of the first planet it encountered, Venus, to assist it on its way to the second, Mercury (see table 3-111).

NASA Headquarters authorized Mariner Mars 69 in late 1965 and assigned the project to the Jet Propulsion Laboratory (JPL). As it had with the earlier Mariner spacecraft, JPL continued its practice of serving as the prime contractor, designing and assembling the two probes in its Spacecraft Assembly Facility in Pasadena, California. Subcontractors contributed various hardware components and subsystems to JPL, and scientists from four institutions provided onboard experiments (see fig. 34). Mariner 6 and 7 lifted off from their launch pads successfully in February and March 1969 and each passed by Mars some five months later. Televisions, infrared radiometers, infrared spectrometers, and ultraviolet spectrometers all performed as planned, with additional data being provided by celestial mechanics and S-ban occultation experiments. Together, the two spacecraft returned 200 television pictures of Mars, which revealed a stark, lunar-like world. Craters ranged in size from 500 meters to 500 kilometers in diameter.

Nothing in Mariner 69's data encouraged those scientists who hoped to discover life on Mars, but neither did it exclude the possibility. NASA engineers and scientists who were already at work on Mariner 71 and Viking learned that they should remain flexible and adaptable as they designed these more sophisticated spacecraft (see tables 3-112, -115, and -116).

With two Mariner 71 orbiters, investigators hoped to map the entire surface of Mars. The 90-day orbits would also allow scientists to observe seasonal changes. NASA assigned four broad goals to Mariner 71: search for an environment that could support exobiological activity; gather information about the origin and evolution of the planet; collect basic data related to planetary physics, geology, planetology, and cosmology; and provide data that would help Viking planners choose touch-down sites for two landers. Orbiter cameras would provide the imagery; ultraviolet spectrometers, and infrared radiometers and spectrometers would provide other clues.

JPL again played the role of spacecraft contractor during Mariner Mars 71, relying on subcontractors to provide it with major components and instruments. These orbiters grew in size, weight, and complexity over their Mariner predecessors, as they were given their new orbital assignment (see fig. 3-5).



Figure 3-4. Mariner Mars 1969.

Figure 3-4. Mariner Mars 1969.



Figure 3-5. Mariner Mars 1971.

Figure 3-5. Mariner Mars 1971.


[206] The Mariner Mars 71 team did not get the chance to perform its two complementary missions. During the launch of Mariner H, the Centaur upper stage malfunctioned, and it and the spacecraft fell into the ocean. Mariner 9 fared better, and it began its orbits around Mars on November 13, 1971, becoming the first spacecraft to orbit another planet. Mars, however, did not cooperate. The worst Martian dust storm ever recorded was just beginning as Mariner 9 made its approach; the dust clouds did not clear until late February 1972. When Mariner 9's high-resolution cameras began recording the features of Mars, the waiting specialists were treated to views of a Mars that were different from those returned by the earlier flyby missions. The crisper images revealed that Mars was a younger, more dynamic planet than was previously believed.

Mariner 9 provided scientists and Viking mission planners with images of 100% of the planet at a resolution of 1 kilometer taken during 349 days in orbit. It also photographed Deimos and Phobos, moons of Mars. Data were also produced on the planet's surface and composition, atmospheric constituents, temperature, pressure, and water content, and surface temperature (see tables 3-113, -117, -118).11

The exploration of Mercury was the primary goal of Mariner 10. Placed into a launch trajectory in November 1973 that took it first by Venus (within 5800 kilometers), the spacecraft used the gravitational force of that planet to reach Mercury. During its 16-month lifetime, Mariner 10 flew by Mercury three times; its closest approach was 327 kilometers. It returned the first television images of this planet closest to the sun, enabling specialists to map 45076 of it, as well as information on the atmospheres and surface of Venus and Mercury. Scientists received their first evidence of the rotating clouds of Venus and the thin helium atmosphere and weak magnetic field of Mercury (see tables 3-114 and -119).

Mariner 10, built by the Boeing Company under contract to JPL, was the first spacecraft to use the gravity of one planet to reach another. The 430-kilogram craft carried six scientific experiments in addition to its television (see fig. 3-6).12

NASA's Office of Space Science and Exploration managed the Mariner program. Donald P. Hearth served as director of the planetary program until 1971, when Robert S. Kraemer assumed the title. A. Thomas Young finished out the decade, becoming director in 1976. N. William Cunningham had the program manager's job for Mariner Mars 69 and Mariner Mercury-Venus 73. Carl W. Glahn....



[207] ....held that position for Mariner Mars 71. Project directors at JPL for these projects reported to the Headquarters program managers. All launches took place at the Kennedy Space Center. The Deep Space Network was employed to support these missions.





Figure 3-6. Mariner Venus/Mercury 1973.

Figure 3-6. Mariner Venus/Mercury 1973.



Figure 3-7. Mariner Venus - Mercury Flight Path.

Figure 3-7. Mariner Venus - Mercury Flight Path.



Planetary landers had been part of NASA's advanced planning since the early 1960s. In 1962, NASA managers approved a large-weight class spacecraft called Voyager that would be designed to visit both Venus and Mars and release landers. Because of budget constraints in the mid-1960s, the Jet Propulsion Laboratory (JPL) was forced to postpone a redefined Voyager Mars 1969 mission, first to 1971 and then to 1973. In August 1967 when Congress reduced NASA's budget once again, NASA terminated all Voyager efforts. When JPL's Voyager Project Office was closed, the project was well defined and in-house and contractor teams were in place to deliver the soft-lander to Mars. To fill the gap left by the cancellation, of Voyager, supporters of planetary exploration at the Langley Research Center (LaRC) and JPL suggested several more modest alternatives.

In late 1967, NASA proposed to Congress two orbiter-probe missions (Titan Mars 1973) to the Red Planet in 1973, to be followed by a more ambitious soft-lander in 1975. President Lyndon B. Johnson approved the idea early in the new year, and together Langley and JPL set to work to define their new projects, until the fall when new budget cuts forced the team to review the Mars missions once again.

NASA Administrator Thomas O. Paine and his space science advisors devised a plan for two combined orbiter-lander missions-called Viking - to replace the two projects already under way. Langley would serve as overall project leader and manager of the lander; JPL would manage the orbiter. One year later, in December 1969, Administrator Paine had to respond to demands from Congress once again. To save money in the years immediately ahead, NASA agreed to postpone the 1973 Mars missions to 1975. (See table 3-120 for a chronology.)

The Viking orbiter, built at JPL, borrowed heavily from Mariner design and technology. Martin Marietta Corporation, under contract to Langley, served as prime contractor for the Viking lander (see fig. 3-8). The two spacecraft were heavily equipped with television cameras and scientific equipment that would allow investigators to examine first-hand the surface of Mars and to search for life forms. Ten separate science teams worked with the designers and engineers at the two NASA centers; the teams included active biology, lander imagery, molecular analysis, entry science, meteorology, radio science, seismology, physical properties, magnetic properties, and inorganic chemistry.

Launched by Titan-Centaur vehicles in the late summer of 1975, Viking I and 2 reached Mars in June and August 1976. The orbiters' high-resolution cameras found a younger, more dynamic planet than earlier Mariners has revealed, and the landing site certification team was forced to look for new safer sites for the two Viking landers. Viking I touched down on the Chryse Plains on July 20, 1976; Viking 2 landed on the Utopia Plains on September 3. The two landers immediately began sending a wealth of imagery and scientific data from the surface (see fig. 3-9), but they did not answer definitively the question of the existence of life on Mars. Biology experiments provided information on the chemical makeup of the samples taken and sensors gave scientists a look at the Martian environment, but the investigations were inconclusive. Scientists could not say that life did not or did exist at the end of the primary mission in November. The orbiters confirmed the presence [214] of water ice on the poles, and lander sensors detected argon and nitrogen in the atmosphere. Instruments sent back a steady stream of weather information, and meteorologists were able to study Martian weather systems through several seasons. NASA conducted an extended Viking mission through April 1978 and continued to monitor signals from the second lander until it was shut down in April 1980. Lander I was still active.

At NASA Headquarters, Walter Jakobowski was Viking program manager in the Office of Space Science. James S. Martin directed Viking as project manager at the Langley Research Center. At JPL, Henry W. Norris served as Viking orbiter manager. The Kennedy Space Center provided launch support; the Deep Space Network, managed by JPL, made communications with the Martian spacecraft possible.13


Figure 3-8. Viking Lander.

Figure 3-8. Viking Lander.


Figure 3-9. Viking Orbiter and Lander During Mission Operations.

Figure 3-9. Viking Orbiter and Lander During Mission Operations.




During NASA's early years the agency was responsible for two separate Pioneer programs: a lunar probe series inherited from the Army and Air Force, and a planetary probe program initiated in 1960. Military teams launched the first four Pioneers (1958-1959), none of which met its mission objectives of lunar reconnaissance. Carrying an experiment package built by the Goddard Space Flight Center, Pioneer 5, launched into orbit around the sun between earth and Venus in 1960, provided investigators with excellent data on interplanetary space. Four more Pioneers of a new design followed (1965-1968), all successfully probing the environment beyond earth. NASA's Ames Research Center at Moffett Field, California, managed this new-generation interplanetary explorer, and TRW served as spacecraft fabricator.

Ames Research Center continued its management of a third-generation interplanetary Pioneer during the 1970s. Pioneer-Jupiter and Pioneer-Saturn would explore these two large planets and then continue their journey outside the solar system. An Atlas-Centaur launched the 258-kilogram TRW-made Pioneer 10 in early 1972 (see fig. 3-10). Charged with 13 experiments designed to capture data on Jupiter and beyond, the spacecraft performed very well. It traveled through the asteroid belt in 1972-1973 unharmed and encountered Jupiter in December 1973. Of special interest to experimenters were the intense magnetic fields surrounding Jupiter and their associated radiation belts, observations of the temperature and structure of the atmosphere, and the color images returned of the planet (see table 3-123). Pioneer 10 became the first spacecraft to pass beyond the known planets in June 1983.

Pioneer 11, of the same design as Pioneer 10, began its voyage toward Jupiter in 1973. Fourteen experiment teams would investigate the interplanetary medium beyond the orbit of Mars, the asteroid belt, and near Jupiter and Saturn. The spacecraft reached the vicinity of Jupiter in 1974 and Saturn in 1979 (see table 3-124).

Pioneer 10 and 11 carried a pictorial plaque designed to inform any scientifically [220] educated beings they might encounter about the planet and people who launched them (see fig. 3-11). The radiating lines on the left side of the diagram represent the position of 14 pulsars, cosmic sources of radio energy, arranged to indicate our sun as the home star of the launching civilization. The man's hand is raised in a gesture of goodwill.

In 1978, NASA launched two Pioneer probes to Venus. Pioneer Venus I went into orbit around Venus in late 1978 and completed into primary mission in August....


Figure 3-10. Pioneer 10/11 Spacecraft.

Figure 3-10. Pioneer 10/11 Spacecraft.

Source: NASA Hq., "Pioneer G Press Kit," Apr. 1, 1973, p. 39b.


[221] .....1979. The 582-kilogram spacecraft carried 17 experiments that measured and analyzed the planet's atmosphere and gravitational field (see table 3-125). Pioneer Venus 2 was a unique spacecraft. Weighing 904 kilograms, it consisted of an overall bus with one large (316-kilogram) and three small (90-kilogram) probes. The vehicle released its scientific payload of hard-landers in November 1978 (see table 3-126). Highly instrumented, the probes were all designated for separate landing zones so that investigators could take in situ readings from several areas of the planet during a single mission. Of primary interest was the nature and composition of the Venusian clouds and the structure of the atmosphere. The large probe survived for more than an hour after impact. Ames Research Center also directed the Pioneer Venus program for NASA.14

At NASA Headquarters, Fred D. Kochendorfer served as program manager for Pioneer and Albert G. Opp was program scientist. Charles F. Hall, project manager, directed the Pioneer 10 and 11 operations at Ames Research Center, where John H. Wolfe was project scientist. Hall continued his role as manager for the Pioneer Venus missions, assisted by L. Colin, project scientist. Launches took place at the Kennedy Space Center. The Jet Propulsion Laboratory operated the Deep Space Network.



Figure 3-11. Plaque carded on Pioneer 10 and 11 designed to demonstrate to scientifically educated inhabitants of some other star system when Pioneer was launched, from where, and by what kind of beings.

Figure 3-11. Plaque carded on Pioneer 10 and 11 designed to demonstrate to scientifically educated inhabitants of some other star system when Pioneer was launched, from where, and by what kind of beings. Design is engraved into a gold-anodized aluminum plate, 152 x 229 mm, attached to spacecrafts' antenna support struts.



[226] Voyager

In the late 1960s, "Voyager" was the name given a large lander unsuccessfully proposed by NASA for a visit to Mars. In 1977, the agency revived the name for its Mariner-class Jupiter-Saturn project. This two-spacecraft project, in part, replaced the "Grand Tour" missions proposed by NASA, in which four spacecraft would have visited the five outer planets during the late 1970s. Two probes would have journeyed to Jupiter, Saturn, and Pluto in 1977, and two others would have made their way to Jupiter, Uranus, and Neptune in 1979. NASA cancelled the tour in early 1972 in response to restrictive budgets. Voyager, proposed later that year, would take advantage of the rare alignment of Jupiter and Saturn in 1977.

The Jet Propulsion Laboratory oversaw Voyager and, as it had with earlier Mariner projects, assembled the two probes on-site in Pasadena, California. Jupiter and Saturn were again the investigators' targets, but Voyager would carry more instrumentation than the earlier Pioneers and provide a more detailed examination of the two planets.

Voyager 1 and 2 were launched in September and August 1977, respectively, by Titan-Centaurs. Even though it was launched second, Voyager I led the way for much of the journey because it was put into a faster, shorter trajectory. The two 822-kilogram spacecraft mission modules were equipped with slow-scan color television for receipt of the first live television images of Jupiter and Saturn, in addition to magnetometers, photopolarimeters, radio astronomy receivers, plasma wave instruments and plasma detectors, ultraviolet spectrometers, and other instruments. Spacecraft designers changed the Mariner design to accommodate the many scientific instruments and imaging equipment, a large antenna, and radioisotope thermoelectric generators (see fig 3-12 and tables 3-127 and -128).

The Voyagers reached Jupiter in January and July 1979 and returned images that excited scientists and the general public alike. (Voyager 1 sent 18 000 images over 98 days, its closest approach being 348 890 kilometers.) They saw the four moons of Jupiter in great detail, active volcanoes on lo, and a ring around the planet similar to the rings of Saturn and Uranus. Voyager 2 recorded 13 000 images of the planet and its satellites. Using the gravity of Jupiter, the Voyagers continued their travels, arriving at Saturn in November 1980 and August 1981. Many of Saturn's secrets likewise were revealed under Voyagers' cameras and instruments. Voyager discovered three new moons and confirmed the existence of others. It was found that the rings of Saturn can be numbered in the hundreds, rather than the few that had been observed before Voyager. In late 1980, Voyager I was on a course that would take it out of the solar system; Voyager 2, deflected by the gravity of Saturn, began heading for Uranus, with an estimated time of arrival of early 1986.15

Rodney A. Mills was Voyager program manager at NASA Headquarters. At the Jet Propulsion Laboratory, John R. Casani and James E. Long served as project manager and project scientist. Kennedy Space Center was the launch site. JPL's Deep Space Network provided mission support.



Figure 3-12. Voyager Spacecraft.

Figure 3-12. Voyager Spacecraft.

Source: JPL, "Voyager Jupiter-Saturn Fact Sheet," Dec. 1976, p. 7.



[229] Other Lunar and Planetary Projects

During Apollo 15 and 16, before the crews began their return journey to earth, astronauts released lunar subsatellites. These particles and fields satellites were designed to gather data related to the moon's magnetic field, lunar gravity, and the solar wind.

The Apollo 15 satellite, released on August 4, 1971, was highly successful, returning data until early 1972 (see table 3-129). Ejected into lunar orbit on April 16, 1972, the Apollo 16 subsatellite was not as successful since it was released into an orbit closer to the moon than planned. The satellite crashed into the lunar surface in May (see table 3-130).




The life sciences program at NASA was always closely allied to the manned spaceflight program, sponsoring studies that evaluated the impact on man of prolonged weightlessness and exposure to the environment of space. In late 1970, the Office of Bioscience Programs officially left the Office of Space Science and Applications (OSSA) to become part of the Office of Manned Space Flight. Areas of study such as exobiology and planetary quarantine were absorbed within OSSA. 16

In addition to the many experiments and observations conducted during Apollo and Skylab missions during NASA's second decade, life scientists conducted one additional flight project, the last Biosatellite mission.



NASA assigned the management of a biological satellite project to the Ames Research Center in October 1962, a time when the agency was keenly seeking data on the effects of space travel on living beings. Running two years behind schedule, the first Biosatellite, which carried 13 experiments with plants, insects, and frog eggs, failed in late 1966 when a retrorocket failure prevented the controlled return of the payload. Biosatellite 2, with the same payload, flew in September 1967 with satisfactory results from a three-day experiment.

Investigators wanted to observe a primate for 30 days on the third and last Biosatellite flight. A 21-day mission to precede Biosatellite 3 had been cancelled in [231] late 1968. The two-part life sciences satellite was launched on June 28, 1969, with a male pigtail monkey named Bonny as a passenger. On July 7, Bonny's health started to fail; he refused to drink and his vital signs were critical: lowering temperature, reduced heart rate, shallow breathing, excessive sleepiness, and sluggishness. Controllers ordered the reentry capsule to separate from the instrument section, which it did, but inclement weather prevented the recovery team from catching the capsule midair. Air Force pilots picked up Bonny minutes after splashdown and flew him to Hickarn Air Force Base in Hawaii. Despite intensive care, Bonny died the next day from causes that were not directly related to his flight. 17

Thomas P. Dallow directed the Biosatellite project at NASA Headquarters. His counterpart at the Ames Research Center was Charles A. Wilson.



* Members of the Space Task Group included Spiro T. Agnew, chairman, Robert C. Seamans, Thomas 0. Paine, and Lee A. Dubridge; U. Alexis Johnson, Glenn T. Seaborg, and Robert P. Mayo were observers.

** Headquarters had also considered the Goddard Space Flight Center, manager of most of the related Explorer satellites, as manager of HEAD. Because MSFC had already begun work on the Apollo Telescope Mount, a large-scale astronomy project, for Skylab and had been reorganized in January 1969 in part to strengthen the role of science at the center, the Office of Space Science and Applications awarded HEAO to MSFC. In addition, HEAO as originally planned was not the class of satellite that GSFC was accustomed to managing.