Mission to Jupiter: A History of the Galileo Project - Comprehensive History of the Epic Exploration of Jupiter and its Moons, Io, Europa, Callisto, Failures and Triumphs (NASA SP-2007-4231)
National Aeronautics and Space Administration (NASA), World Spaceflight News, Michael Meltzer
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MISSION TO JUPITER: A History of the Galileo Project
Michael Meltzer
National Aeronautics and Space Administration * NASA History Division * Washington, DC 2007
NASA SP-2007-4231
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Chapter 1 * The Importance of the Galileo Project
Chapter 2 * From Conception to Congressional Approval
Chapter 3 * The Struggle to Launch Galileo: Technical Difficulties and Political Opposition
Chapter 4 * The Challenger Accident and Its Impact on the Galileo Mission
Chapter 5 * The Galileo spacecraft
Chapter 6 * Galileo Deployment, the Inner Solar System Tour, and the Asteroid Belt
Chapter 7 * The High-Gain Antenna Failure: A Disappointment and a Challenge
Chapter 8 * Jupiter Approach and Arrival
Chapter 10 * Profiles of Selected People Important to the Mission
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Preface
The Galileo Project: Commitment, Struggle, and Ultimate Success
I am glad to see that someone has followed through and done a really comprehensive and workman-like job capturing the history of the Galileo project. This book goes all the way back to the initiation of the project, when it was more or less just a thought in a few peoples' minds, and traces the whole evolution from there. I got a great deal out of reading it.
I have a vested interest in the Galileo project—I was deeply involved in it for over a decade. A lot of people know about the mission and its terrific science return, but they don't know about the struggle putting the project together, getting it started, and keeping it going through all of the reprogramming and restructuring. One of the arguments that we used with people on Capitol Hill to keep the program alive through delays in the congressional budgeting process was that Galileo would be a nonthreatening manifestation of our country's technological capabilities, and this would send a powerful message to the rest of the world. It did just that.
Galileo meant a lot to the United States, but it also meant a lot to our space science community, because at the time that we were going through the development of Galileo, it was the only major deep space project. There were Earth satellite launches going on, but nothing to the planets. It was Galileo that really helped NASA and the U.S. space science community maintain viability during a period of extreme drought in program development. A lot of capability would have disappeared over the course of the 10 years that Galileo was in development.
The commitment that individuals made to Galileo was extraordinary. Many individuals committed a third or more of their professional lifetimes to executing this project. Over the years, situations developed so many times where it looked like there was just no way out for the project, but we always managed to come up with a solution. The number of times we managed to pull the fat out of the fire was truly remarkable.
The Galileo project was complex in that it required funding for science instrument and spacecraft development from numerous sources, including NASA and its Centers, the Department of Energy, U.S. universities, and the Europeans (especially the Germans). Just how the pieces of the fabric were woven together into what turned out to be a very successful program—one that required an investment of almost two decades of preparatory and execution work to bring about—is an interesting story. Revisiting the program from a historical point of view is what motivated me to read this book. I think that people who are interested in the space program, its science achievements, and its contribution to technology in general will really appreciate this history. It's comprehensive, it's complete, and it seems to me to be pretty even-handed. I'm very appreciative of what Michael has done.
—John Casani, First Galileo Project Manager
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Foreword
We Are All Standing on the Bridge of Starship Enterprise
This book details the history of the Galileo mission. Galileo had political ups and downs, technical challenges and hurdles, and was a multigenerational task. We had people starting the mission on advisory committees and senior management jobs who have now passed on. Many people went through parts of Galileo in stages of their careers. I have friends who still mark their anniversaries and the birthdates of their children in terms of, "That was when we were on the beginning stages of prelaunch preparation," or, "It was during our first Europa encounter when that happened." The Galileo team felt much more as a family than a pure professional enterprise. People worked together for long periods of time, through good times and bad, to accomplish this thing not just for them, but for everybody.
The Galileo mission to Jupiter was part of the grand sweep of solar system exploration. You can view planetary exploration as a human endeavor—a wave sweeping outward from Earth. We went to the close-in places first—the Moon, Venus, and Mars. The outer solar system was the next big frontier, and it was an order of magnitude more difficult to explore. The distances are truly staggering, and the problems of developing spacecraft that could survive on their own for long periods of time were major challenges.
The early explorations of the outer solar system were performed by relatively fast-trajectory spaceships, like the Pioneers and Voyagers. They and Galileo were major steps forward in being able to develop reliable craft that would operate for decades, continue to send data back without failing, and be smart enough to take care of themselves out of communication with Earth. At Jupiter, the time available to send a radio signal is typically 45 minutes, and another 45 minutes before you get an answer back. You are well beyond being able to do the types of things that can be done in Earth orbit.
NASA's outer solar system missions helped turn that region into a known place, rather than just the realm of astronomers. The outer solar system became someplace that can be talked about and thought about in geological and geophysical terms. The person on the street and kids in school can say, "Hey, I saw a picture of a moon of Jupiter the other day and it had volcanoes on it."
We planned the Galileo mission in that context. The scientific advisory committees to NASA and the U.S. government laid out an exploration strategy of fast reconnaissance missions followed by missions such as Galileo, in which we orbited planets and did more detailed studies. There was a leapfrogging characteristic to this type of exploration. The missions take so long to plan and execute that the next wave of exploration must be prepared even before the current one can be launched. We began work on Galileo in 1972 in its infant form, and we really got to work on it in 1974 with detailed studies, even before Voyager was launched in 1977.
On Galileo, we combined orbital and in situ exploration strategies. We believed that if we were going through so much effort and so many resources to get there, we ought to not only study the planet, its satellites, and magnetic fields, but that we also should understand the chemistry of the atmosphere in detail with an entry probe that actually went into the atmosphere, grabbed a sample, analyzed it, and sent the data back to the mother ship before burning up in the atmosphere. This was very ambitious.
We had a strategic plan that said we were going to go orbit Jupiter, get into its atmosphere, and then inform that plan with tactics derived from Voyager results. It is a good example of the way exploration progresses. You learn things that lead to new questions you want to answer, and so forth. We were preparing to follow up and understand Jupiter's miniature planetary system at a very detailed level, even as Voyager was continuing on from Jupiter to Saturn, opening up the rest of the outer solar system.
People frequently ask, "Why should the average person be interested in what's going on in the Jupiter system?" There are answers to that on all levels, ranging from the visibility of high technology to developing new things that have spinoffs to enhancing national prestige to satisfying pure curiosity. But really, it is all about changing the way we look at the universe and the world. We want to know how planets tick and understand the processes that control us here on Earth—everything from geophysics to climatology to global warming. The universe is effectively a laboratory waiting for us to study these things.
Most of the people who have worked on Galileo over the years probably regard their biggest contribution as having changed the textbooks. Kids today learn about such things as the moons of Jupiter, and they know what they're talking about. To them, the planets become not just dots in the sky that you can barely see with a telescope. The planets become real places, and kids know their characteristics.
There is always a tension in the national debate about how much robotic exploration (such as Galileo) we should do versus so-called human exploration (such as Apollo). This misses the point! What we call robotic exploration is in fact human exploration. The crews sitting in the control room at Jet Propulsion Laboratory as well as everyone out there who can log on to the Internet can take a look at what's going on. So, in effect, we are all standing on the bridge of Starship Enterprise.
It is important to note that Galileo was an international mission. Science is, by its nature, international. We had people contribute from countries all over the European community and other countries as well. This was one of the first missions in which the analysis of data more or less continued around the clock, around the globe. We'd wake up in the morning and hear that one of our colleagues in Berlin had processed some images overnight and brought new data to the table—and we could look at it immediately, while they had a chance to sleep.
The intellectual children, grandchildren, and great-grandchildren of the people who worked on Galileo have now spread through the crews operating the Cassini spacecraft at Saturn and the MER Rovers, Spirit and Opportunity, on the surface of Mars. It is an ongoing spirit of exploration and, to me, that's really the bottom line of what Galileo was all about. It is important to record the history of these types of things, both because of the intrinsic interest that the public has and because there are always lessons to be learned. I sure hope people will read this book and get that feeling from it.
—Torrence V. Johnson, Galileo Chief Scientist
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Acknowledgments
So many people gave me valuable input for this book. I want to thank them for their time and interest in this project. Some of these people include:
Torrence V. Johnson, who related with eloquence how decisions were made and operations were carried out on the mission.
John Casani, whose project leader perspectives on the mission's importance and on the political battles that had to be fought were hugely important for my book. Also, thank you to the mission's other project managers: Dick Spehalski, Bill O'Neil, Bob Mitchell, Jim Erickson, Eilene Theilig, and Claudia Alexander, all of whom gave me valuable insights on what Galileo was all about.
Thanks go out to the mission engineers and technicians at Jet Propulsion Laboratory (JPL), especially Nagin Cox, who is indeed a poet when she talks about Galileo, Gerry Snyder, Duane Bindschadler, Brad Compton, Gregory C. Levanas, Theodore Iskendarian, and various members of the Galileo mission support crew; experts from Ames on the Probe, including Charlie Sobeck, Ed Tischler, and Joel Sperans; and Krishan K. Khurana of UCLA. Also, thanks to Dick Malow, a former congressional committee staff director; Allan J. McDonald of Thiokol Propulsion; Carl Fromm for his help and encouragement; Julie Cooper for patient help in finding graphics for the book; and Craig Waff for sharing his extensive research on the Galileo mission. In addition, a special thanks goes to the staff of JPL Archives, especially Russell Castonguay, who was incredibly helpful in locating long-buried letters and documents.
At NASA Headquarters, the History Division staff, in particular, former NASA Chief Historian Roger Launius and the current NASA Chief Historian Steven Dick, deserve much credit for their support and oversight. Archivists Colin Fries and Jane Odom helped a great deal by finding and organizing essential archival material. Steve Garber oversaw the production process. Interns Liz Suckow, Jennifer Chu, Giny Cheong, and Gabriel Okolski all helped tremendously in obtaining and organizing images.
Also at NASA Headquarters, the talented professionals in the Office of Printing and Design deserve much credit. Lisa Jirousek and Dyana Weis carefully copyedited the manuscript, designers Cathy Wilson and Smahan Upson laid out the manuscript in a very attractive manner, printing specialists Jeffrey McLean and Henry Spencer handled this crucial last step, and supervisors Steven Johnson and Gregory Treese managed the whole process.
And finally, a thank you to my wife, Naisa Kaufman, for her talented and tough manuscript editing.
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Introduction: Meeting the Grand Challenge
In an address to the U.S. Senate Subcommittee on Science, Technology, and Space, author James Michener asserted that "it is extremely difficult to keep a human life or the life of a nation moving forward with enough energy and commitment to lift it into the next cycle of experience . . . . There are moments in history when challenges occur of such a compelling nature that to miss them is to miss the whole meaning of an epoch. Space is such a challenge."1
The Galileo mission to Jupiter successfully explored a vast new frontier, had a major impact on planetary science, and provided invaluable lessons for the design of subsequent space vehicles. In accomplishing these things, Galileo met the challenge of "such a compelling nature" that Michener envisioned. The impact of the mission was felt by those who worked on it, the country that supported it, and the people from other parts of the world who were deeply impressed by it. In the words of John Casani, the original Project Manager of the mission, "Galileo was a way of demonstrating . . . just what U.S. technology was capable of doing."2 An engineer on the Galileo team expressed more personal sentiments when she said, "I had never been a part of something with such great scope . . . . To know that the whole world was watching and hoping with us that this would work. We were doing something for all mankind . . . I'd walk outside at night and look up at Jupiter, and think, my ship's up there."3
Like other grand voyages of discovery, Galileo altered the way we view our surroundings (in this case, our planetary surroundings). It is thus fitting that this mission to the Jovian system was named after a man whose own astronomical observations radically challenged the way that people of his time viewed their universe. The discoveries of both Galileo the man and Galileo the spacecraft brought us new perceptions of our planetary system, made our lives richer and more interesting, and breathed new vitality into our quest to understand ourselves and our universe.
1 James A. Michener, "Space Exploration: Military and Non-Military Advantages" (speech delivered before the U.S. Senate Subcommittee on Science, Technology, and Space, Washington, DC, 1 February 1979). Published in Vital Speeches of the Day (Southold, NY: City news Publishing Company, 15 July 1979).
2 John Casani interview, tape-recorded telephone conversation, 29 May 2001.
3 Nagin Cox interview, tape-recorded telephone conversation, 15 May 2001.
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The Importance of the Galileo Project
When the Galileo spacecraft launched on 18 October 1989, it began an interplanetary voyage that took it to Venus, two asteroids, back to Earth (twice), and finally on to Jupiter. It studied the planet's intense magnetic fields, belts of radiation, and high-energy particles, and it sent off a planetary probe that accomplished the most difficult atmospheric entry ever attempted. The Galileo spacecraft repeatedly swooped by Jupiter's Galilean moons, using a suite of scientific instruments to delve into their structures and properties. The mission amassed so many scientific "firsts" and key discoveries that it can truly be called one of the most impressive feats of exploration of the 20th century. The Galileo mission added dramatically to our understanding of the Jovian system and our entire solar system. Moreover, the mission was a triumph of teamwork and ingenuity under exceedingly difficult conditions.
The Lure of Jupiter for People on Earth
For centuries, the Jovian system has stirred our imaginations and been the frequent subject of our observations. The astronomer Galileo Galilei, using an early telescope that he himself made, discovered that Jupiter was not only a planet, but also the center of its own system of moons. This discovery called into question the Aristotelian-Ptolemaic view of the universe, which was accepted at the time by the Catholic Church, that all things revolve around Earth and, by extension, us. Thus, there could be only one center of revolution, and yet, Jupiter did not appear to obey that law.2
The Aristotelian-Ptolemaic model held that Earth was fundamentally different from the other planets in that it was "corruptible," "alterable," and "naturally dark and devoid of light."3 Earth, it was thought, was also the only planet accompanied by a moon. Galileo's discovery showed that this was not so. Jupiter was more like Earth than had been previously imagined. Using this new knowledge, Galileo argued that Earth indeed might not be fundamentally different from the other planets in additional ways. In his 1632 treatise entitled A Dialogue Concerning the Two Chief World Systems, Galileo used his discovery of the Jovian moons, as well as many other observations of Jupiter, the other planets, and Earth's Moon, to defend the Copernican model of our planetary system. In Copernicus's view, Earth was not immovable. All of the planets, including Earth, revolved around the Sun. Such a concept challenged the anthropocentric ideas of the time and flew in the face of official Church doctrine.4
Jupiter's sheer size and energy have added to our interest in the planet. It is one of the brightest objects in the night sky. Unlike other planets, it emits more thermal radiation than it absorbs from the Sun. It is also a radio-wave source. A storm bigger than Earth (the Great Red Spot) has been raging on its surface for centuries.
Jupiter contains 75 percent of the total nonsolar matter in the solar system. The planet is so big that it constitutes a transitional object between a terrestrial-type planet and a star. Its composition—mainly hydrogen and helium—is closer to the Sun's composition than to that of Earth.
Another important aspect of Jupiter is the effect that its enormous gravity has on its satellites. Nowhere else in the solar system do planets interact so strongly with their moons. In particular, Jovian gravity causes mammoth tides and extensive volcanism on the satellite Io, the most tectonically active body in the solar system. Geological changes occur so rapidly on Io that in the space of only five months, Galileo was able to observe significant alterations in a large section of the moon's surface (see the Io section in chapter 9 for a fuller discussion of these observations).
The Galileo mission was the first to provide extended observations of Jupiter's dynamic magnetic fields. The Jovian magnetosphere is the largest of any planet's, so expansive that it could envelop the Sun and much of its corona. If our eyes could see magnetic field lines, Jupiter's magnetosphere would appear larger than our Moon, in spite of its distance from us.
Finally, Jupiter is a window into our own past. Many scientists believe that the composition of the planet is little altered from that of the original solar nebula. As such, the Galileo spacecraft's observations provided a look back in time to the early stages of our solar system. Being able to perform such an examination was important because it helped untangle the "bewildering array of processes and phenomena which have affected the evolution of the planets and which control their environments and futures."5
Galileo: A New Phase in the Study of the Outer Planets
The two Voyager spacecraft, which launched in 1977, completed visits to all of the planets known to ancient astronomers. The Galileo mission began a different phase in the study of the outer planets: an era of more careful, systematic study, featuring close flybys and in-depth analyses of planetary system characteristics.6
Galileo was not a Jupiter mission in the traditional sense of the term, which typically refers to a project focusing on a single target. Galileo's objectives were much broader, encompassing a holistic analysis of the entire Jovian system of satellites, primary planet, magnetic fields, and particle distributions.
Galileo's Impact on Future Deep Space Missions
The Galileo project team's approach to exploration, spacecraft technical design, and operational problems will all strongly affect the manner in which other projects are conducted in the decades to come. Among the Galileo mission's memorable achievements were the repeated successes of its staff in solving serious technical problems, even though the spacecraft was hundreds of millions of miles from home. Examples include the responses of the team to the high-gain antenna deployment failure and to the jamming of the spacecraft's data tape recorder, both of which will be discussed in detail in later chapters. In each instance, the team attacked potentially mission-ending problems and found ingenious ways to keep the spacecraft operational and productive. Results of these efforts, such as enhancement of the Deep Space Network (DSN) and development of new data-compression software, constituted technological improvements that will benefit future missions as well.
The Many Firsts of Galileo
Galileo was the first deep space mission designed to launch on an expendable launch vehicle from the Space Shuttle's payload bay rather than from Earth. This was not a trivial achievement. Designing enough thrust into the craft to reach Jupiter while carrying its large, sophisticated payload took a great deal of creativity, especially after the Challenger disaster precluded the use of liquid fuel due to safety considerations.
The Galileo mission was also the first to make a close flyby of an asteroid (Gaspra), discover an asteroid moon (Ida's satellite Dactyl), orbit a gas giant planet (Jupiter), send a probe down into the Jovian atmosphere, and make direct observations of a comet (Shoemaker-Levy) smashing into a planet.7
Other Milestone Accomplishments
The Galileo spacecraft made two flybys of Earth before leaving the inner solar system, using our planet's gravity to alter its trajectory in critical ways. During these flybys, the spacecraft made important observations of our Earth-Moon system. For instance, the spacecraft confirmed the existence of a huge impact basin on our Moon's far side that had been inferred, but never observed, from Apollo data. Galileo also provided evidence of more extensive volcanism on the Moon than previously thought.8
To reach Jupiter, Galileo traveled 2.4 billion miles at an average speed of 44,000 miles per hour (mph). After leaving Earth, it required only 67 gallons of fuel to control its flight path and orientation. So accurate was Galileo's trajectory that the craft missed its target point near the Jovian moon Io by a mere 67 miles. This feat has been likened to shooting an arrow from Los Angeles to New York and missing a bull's-eye by 6 inches.9
On its way to Jupiter, Galileo discovered the most intense interplanetary dust storm ever observed. It found a very strong radiation belt above Jupiter's cloud tops and Jovian wind speeds exceeding 720 kilometers per hour (450 miles per hour, or mph). These speeds remained fairly constant to depths far below the clouds, unlike the jetstreams on Earth. Probe measurements within the Jovian atmosphere revealed a surprisingly small amount of water compared to what had been expected from Voyager observations, as well as far less frequent lightning than predicted. The Probe observed only one-tenth the lightning activity per unit area of that found on Earth, although the strength of individual events exceeded those on Earth by an order of magnitude.10
The spacecraft observed that Jovian helium abundance (24 percent) is very nearly that of the Sun (25 percent)—one reason why Jupiter can be considered a transitional object between a planet and a star. From magnetic data collected by Galileo, scientists suspect that Ganymede, the largest Jovian satellite, creates its own magnetic field by means of an Earth-like dynamo mechanism within its core. This was the first moon found to exhibit such magnetic field characteristics. But the most dramatic and important discovery, according to many on the Galileo team, was the strong evidence of a deep saltwater ocean beneath the icy crust of the moon Europa. Such an ocean could conceivably harbor simple forms of life.11
The Multiteam Cooperation Required To Develop the Galileo Spacecraft
The success of the Galileo mission was partly due to the efficient management of an incredibly complex and diverse network of specialist teams. such a network was required to develop the sophisticated spacecraft that could perform the many mission functions required.
The Galileo spacecraft was characterized by its highly integrated design. Its diverse subsystems, developed by different project teams, needed to interface flawlessly with each other over many years. subsystem dependencies needed to be fully understood and controlled because the environment experienced by a typical subsystem was strongly affected by the behavior of other connected subsystems. For example, the limited electric power that was available aboard Galileo had to be shared by temperature control and many other spacecraft subsystems in a manner that minimized energy use. Large temperature swings inside the spacecraft could result from this situation, and this placed stringent design requirements on the subsystems that had to withstand those swings.12
The task that had been laid before Galileo project management13 was to design, fabricate, test, modify as needed, and ultimately fly the highly integrated, complex spacecraft. to accomplish this, communications among a large number of different organizations had to be smooth and effective. the lead NASA field center for the project was the Jet propulsion laboratory (JPL) of the California Institute of Technology, working for NASA's Solar System Exploration Division. Galileo's Orbiter, which conducted extensive flybys of Jupiter and its moons, was developed by JPL, operating in close coordination with a range of university, industry, and government laboratory groups.
Galileo's Jupiter probe, which entered the planet's atmosphere, was designed by NASA's Ames Research Center and manufactured by Hughes Aircraft Company under contract to Ames. the U.S. Department of Energy provided the plutonium-powered electrical generators that ran the various spacecraft functions. NASA's Lewis Research Center (now known as Glenn Research center) helped develop the propulsion system and integration of the payload with the Space Shuttle. the Shuttle itself was supplied by Johnson Space Center, while Kennedy Space Center made available launch and landing facilities.
The Galileo Project also involved international cooperation with the Federal Republic of Germany, which provided instrumentation for both the Orbiter and the probe, a propulsion system for the Orbiter, and telemetry and command support from the German Space Operations Center.14
The agreements forged in this project established a context for future space missions and the activities and complexities that surround them. Important management lessons were learned from the international nature of the mission. For instance, when mission-critical equipment is being designed, manufactured, and tested by other countries, NASA needs to create parallel organizations in both the managing country and "subcontractor" countries to handle the day-to-day coordination issues that arise.
During the Galileo Project, parallel organizations in the United States and Germany developed a contractual instrument called an "Interface Requirements Document" (IRD) that contained all the technical specifications for both the propulsion system being built in Germany and its interface with the U.S.-built Orbiter. The IRD gave the United States a vital measure of control over the work performed by Germany. Contractual arrangements, however, necessitated the development of the IRD early in the project, while the spacecraft design was still in a period of flux. A great deal of time, more than originally planned, was expended by both countries in negotiating acceptable designs and verification procedures for the propulsion system development. The unplanned time and effort, which were deemed necessary due to the mission-critical nature of the propulsion system, resulted in unforeseen costs and delays.
NASA might have avoided the above cost overruns and schedule delays if it had not placed responsibility for mission-critical equipment in one country and project management in another. Lessons learned from the Galileo experience were implemented in planning the International Solar Polar Mission, in which NASA and the European Space Agency each took on the responsibility of designing and fabricating functionally independent spacecraft. A similar management model could be applied to an international Orbiter/Probe effort by assigning one nation the job of developing the Orbiter and another nation the job of delivering the Probe.15
Importance of Galileo for the U.S. Space Program
John Casani, Galileo's first Project Manager, believed that our country's space exploration program has had strong benefits. It has elicited worldwide respect and admiration for the United States and has effectively demonstrated, in a nonthreatening way, our country's technological capabilities. Moreover, our space program has been a source of pride and inspiration for millions of Americans, as well as a motivation for young people to pursue careers in science and technology. Our ventures into space have demonstrated, loud and clear, that the U.S. holds a position of unparalleled preeminence in the fields of space science and space technology.16
The Galileo mission was critical for preserving NASA's planetary exploration capability and for advancing the technology and survivability of robotic spacecraft. Galileo was an international cooperative program that strongly demonstrated to the European community the dependability of U.S. space exploration commitments. Such a demonstration was especially pertinent because it came in the wake of the International Solar Polar Mission's termination.17
Galileo was a cornerstone of NASA's planetary exploration program and achieved the highest scientific objectives for the outer solar system. The project maintained high visibility in a very positive manner for the United States at what can be considered a modest cost. During Galileo's development, the entire planetary exploration program constituted only 5 percent of NASA's budget, which was in turn only 1 percent of the federal budget.18
In its 1981 budget authorization, the U.S. Senate's Committee on Commerce, Science and Transportation recognized the importance of the Galileo mission, as well as that of the rest of the planetary exploration program. the committee noted the "spectacular accomplishments" of the exploration program, particularly with respect to the investigation of Saturn, Jupiter, Venus, and Mars. The Senate Committee was concerned, however, about the four-year gap that would occur between Voyager 2's 1981 encounter with Saturn and its encounter with Uranus, as well as the dearth of planetary imaging data that would result during this time. The Committee expressed its strong support for our country's world leadership position in planetary exploration but was quite apprehensive about other nations' aggressive programs in this area. In particular, the Committee regretted the lack of planned U.S. representation in missions to Halley's Comet when it made its closest approach to the Sun in 1986. The Soviet Union, France, and other European nations, as well as Japan, were all developing missions to investigate the comet.19
The U.S. House of Representatives Committee on Science and Technology concurred with the Senate's concerns, commenting that the House Committee would "not preside silently over this abandonment of U.S. leadership in planetary exploration." The House Committee went on to point out the need to "nurture planetary science with new data," expressing the fear that "where there is no new information to work with, a vital science becomes arid academic speculation."20
The Committee also commented that it considered NASA's civilian programs a "national resource" that has contributed substantially to the U.S. economy and our scientific preeminence. Results from these programs have, in the Committee's view, added to our understanding of the universe and to key questions regarding life, matter, and energy.21
How Important Is Our Need To Continually Pioneer New Frontiers?
Throughout human history, we have repeatedly wondered about the nature of our universe and have sought to understand it better. Ancient Greek, Roman, Chinese, Arabic, Egyptian, Mayan, and many other cultures expended considerable resources trying to fathom what lay beyond their immediate lines of sight. These early scientific quests resulted in bodies of knowledge that continue to inspire today's space scientists.22
Plato sensed the significance of these types of inquiries. In Republic VII, Socrates asked, "Shall we make astronomy the next study?"23 Glaucon replied that certainly they should, listing the practical benefits that a knowledge of seasons and lunar and solar cycles have for everyone, from military commanders to sailors and farmers. But Socrates chided Glaucon for his eminently sensible view, hinting that astronomy may be important to study even if it is not immediately profitable. Former NASA Administrator James C. Fletcher spoke much more directly to this point when he linked the study of space to the highest of human endeavors—the "salvation of the world."24
The benefits of space exploration, as well as scientific research in general, have never been easy to quantify in terms of dollars and cents, although we have identified various ways in which such activities enrich us. Reaching out into space and developing the technology to make this possible have added to our understanding of Earth, our solar system, and the universe that surrounds us. Increasing our knowledge of these things is satisfying in its own right—we feel wiser and better knowing more about our universe. But our quest is also highly practical. The technology we develop can help improve our lives. Furthermore, we must make sure that control of space by other nations is not used to endanger our national security. Our explorations help prepare us to use our access to space to defend ourselves if necessary.
We enhance our country's prestige among the peoples of the world by successful endeavors beyond our atmosphere, while at the same time adding to our scientific, technological, industrial, and military strength. Last but not least, we satisfy the compelling urge of our species to explore and discover, to set foot where no one else has. Our unstoppable curiosity distinguishes us from other species on our planet. Since Earth's surface has largely been explored, we must now turn our gaze upward and outward. 25
1 Statement by Torrence V. Johnson, Galileo chief scientist. Reported in "Galileo's Bounty," San Francisco Chronicle (31 July 2000): A4.
2 Office of the Vice President of Computing, Rice University, "Jupiter and Her Moons: One Planet's Quest to Defy Aristotle," The Galileo Project, http://es.rice.edu/ES/humsoc/Galileo/Student Work/Astronomy95/jupiter.html (accessed 25 July 2003).
3 Galileo Galilei, A Dialogue Concerning the Two Chief World Systems, 1632, available online at http://webexhibits. org/calendars/year-text-Galileo.html (accessed 24 July 2003).
4 Roger D. Launius and Steve Garber, "Galileo Galilei," Biographies of Aerospace Officials and Policymakers, E-J, National Aeronautics and Space Administration (NASA) Office of Policy and Plans, http://www.hq.NASA.gov/office/ pao/History/biosej.html (accessed 20 November 2001); "Nicolaus Copernicus," JOC/EFR, University of St. Andrews, Scotland, November 2002, http://www-history.mcs.st-andrews.ac.uk/history/Mathematicians/Copernicus.html; A. Mark Smith, "Galileo," World Book Online Americas Edition, http://www.worldbookonline.com/ar7/na/ar/co/ ar215300.htm (accessed 20 March 2003); Galileo Galilei, A Dialogue.
5 T. V. Johnson, C. M. Yeates, and R. Young, "Space Science Reviews Volume on Galileo Mission Overview," Space Science Reviews 60.1-4 (1992): 5-6.
6 Eric G. Chipman, Donald L. De Vincenzi, Bevan M. French, David Gilman, Stephen P. Maran, and Paul C. Rambaut, "The Worlds That Wait," chapter 7-2 in A Meeting with the Universe: Science Discoveries from the Space Program (Washington, DC: NASA Publication EP-177, 1981), http://www.hq.NASA.gov/office/pao/History/EP-177/ch7-2.html (accessed 20 March 2000).
7 National Space Science Data Center, "Galileo Project Information," http://nssdc.gsfc.NASA.gov/planetary/galileo.html, p. 2 (accessed 11 March 2000).
8 "Galileo Project Information," pp. 2-3.
9 Everett Booth, "Galileo: The Jupiter Orbiter/Space Probe Mission Report," December 1999, p. 19, JPL internal document, Galileo — Meltzer Sources, folder 18522, NASA Historical Reference Collection, Washington, DC.
10 "Galileo Project Information," p. 3; Donald J. Williams, "Jupiter—At Last!" Johns Hopkins APL Technical Digest 17:4 (1996): 347, 354; "The Probe Story: Secrets and Surprises from Jupiter," Galileo Messenger (April 1996): 3.
11 "Galileo Project Information," p.3; Booth, p.9.
12 R. J. Spehalski, "Galileo Spacecraft Integration: International Cooperation on a Planetary Mission in the Shuttle Era," Earth-Orient. Applic. Space Technol. 4.3 (1984): 139.
13 John R. Casani of JPL was the Project Manager during most of Galileo's development.
14 Spehalski, "Galileo Spacecraft Integration," pp. 139-140.
15 Ibid., pp. 148-150.
16 John R. Casani to Thomas G. Pownall, President, Martin Marietta Corporation, "Why Galileo?" 8 December 1981, John Casani Collection, Galileo Correspondence 11/81-12/81, folder 24, box 3 of 6, JPL 14, JPL Archives.
17 Casani, "Why Galileo?" p. 2.
18 John R. Casani to Fred Osborn, 4 December 1981, John Casani Collection, Galileo Correspondence 11/81-12/81, folder 24, box 3 of 6, JPL 14, JPL Archives.
19 Senate Authorization Report No. 97-100 (p. 37), Committee on Commerce, Science and Transportation, John Casani Collection, Galileo Correspondence 11/81-12/81, folder 24, box 3 of 6, JPL 14, JPL Archives.
20 House of Representative Report No. 97-32 (pp. 11-8 and -9, 12-10, 16-20), Committee on Science and Technology, John Casani Collection, Galileo Correspondence 11/81-12/81, folder 24, box 3 of 6, JPL 14, JPL Archives.