To See the Unseen: A History of Planetary Radar Astronomy - A Comprehensive History of Radar Observations of Venus, Mars, Comets, Asteroids, the Magellan Mission, Arecibo Observatory (NASA SP-4218)
National Aeronautics and Space Administration (NASA), World Spaceflight News, Andrew J. Butrica
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To See the Unseen: A History of Planetary Radar Astronomy
by Andrew J. Butrica
The NASA History Series * NASA History Office * Washington, D.C.
1996
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The past 50 years have brought forward a unique capability to conduct research and expand scientific knowledge of the Solar System through the use of radar to conduct planetary astronomy. This technology involves the aiming of a carefully controlled radio signal at a planet (or some other Solar System target, such as a planetary satellite, asteroid, or a ring system), detecting its echo, and analyzing the information that the echo carries.
This capability has contributed to the scientific knowledge of the Solar System in two fundamental ways. Most directly, planetary radars can produce images of target surfaces otherwise hidden from sight and can furnish other kinds of information about target surface features. Radar also can provide highly accurate measurements of a target's rotational and orbital motions. Such measurements are obviously invaluable for the navigation of Solar System exploratory spacecraft, a principal activity of NASA since its inception in 1958.
Andrew J. Butrica has written a comprehensive and illuminating history of this little-understood but surprisingly significant scientific discipline. Quite rigorous and systematic in its methodology, To See the Unseen explores the development of the radar astronomy specialty in the larger community of scientists.
More than just a discussion of the development of this field, however, Butrica uses planetary radar astronomy as a vehicle for understanding larger issues relative to the planning and execution of "big science" by the Federal government. His application of the "social construction of science" and Kuhnian paradigms to planetary radar astronomy is a most welcome and sophisticated means of making sense of the field's historical development.
Andrew J. Butrica received his Ph.D. in the history of science and technology at Iowa State University. He is a research historian in Franklin Park, New Jersey, specializing in the history of science. In 1990 Praeger Publishers issued his Out of Thin Air: A History of Air Products and Chemicals, Inc., 1940-1990.
Dedication
To my dear friends and former colleagues at the Center for Research in History of Science and Technology: Bernadette Bensaude-Vincent, Christine Blondel, Paulo Brenni, Yves Cohen, Jean-Marc Drouin, Irina and Dmitry Gouzevitch, Anna Guagnini, Andreas Kahlow, Stephan Lindner, Michael Osborne, Anne Rasmussen, Mari Williams, Anna Pusztai, and above all Robert Fox.
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Chapter Three: Sturm und Drang
Chapter Four: Little Science/Big Science
Chapter Six: Pioneering on Venus and Mars
Chapter Eight: The Outer Limits
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Acknowledgments
From Locksley Hall
For I dipt into the future, far as human eye could see, Saw the Vision of the world, and all the wonder that would be; Saw the heavens fill with commerce, argosies of magic sails, Pilots of the purple twilight, dropping down with costly bales; Heard the heavens fill with shouting, and there rained a ghastly dew
From the rations' airy navies grappling in the central blue
Far along the world-wide whisper of the south-wind rushing warm, With the standards of the peoples plunging through the thunder-storm; Till the war-drum throbbed no longer, and the battle-flags were furled In the Parliament of man, the Federation of the world.
There the common sense of most shall hold a fretful realm in awe, And the kindly earth shall slumber, lapt in universal law. So I triumphed ere my passion sweeping through me left me dry, Left me with the palsied heart, and left me with the jaundiced eye; Eye, to which all order festers, all things here are out of joint: Science moves, but slowly slowly, creeping on from point to point:
Alfred Baron Tennyson (1842)
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Let me begin with a confession and some explanations. Before beginning this project, I knew nothing about planetary radar astronomy. I quickly realized that I was not alone. I discovered, too, that most people confuse radar astronomy and radio astronomy. The usual distinction made between the two is that radar astronomy is an "active" and radio astronomy a "passive" form of investigation. The differentiation goes much deeper, however; they represent two disparate forms of scientific research.
Radio astronomy is more akin to the methods of natural history, in which observation and classification constitute the principal methods of acquiring knowledge. Radio astronomers search the cosmos for signals that they then examine, analyze, and classify. Radar astronomy, on the other hand, is more like a laboratory science. Experimental conditions are controlled; the radar astronomer determines the parameters (such as frequency, time, amplitude, phase, and polarization) of the transmitted signals.
The control of experimental parameters was only one of many aspects of planetary radar astronomy that captivated my interest, and I gradually came to find the subject and its practitioners irresistibly fascinating. I hope I have imparted at least a fraction of that fascination. Without the planetary radar astronomers, writing this book would have been a far less enjoyable task. They were affable, stimulating, cooperative, knowledgeable, and insightful.
The traditional planetary radar chronology begins with the earliest successful attempts to bounce radar signals off the Moon, then proceeds to the detection of Venus. I have deviated from tradition by insisting that the field started in the 1940s and 1950s with the determination by radar that meteors are part of the solar system. Meteor, auroral, solar, lunar, and Earth radar research, as well as radar studies of planetary ionospheres and atmospheres and the cislunar and interplanetary media are specializations in themselves, so were not included in this history of planetary radar astronomy in any comprehensive fashion. What has defined radar astronomy as a scientific activity has changed over time, and the nature of that change is part of the story told here.
This history was researched and written entirely under a contract with the California Institute of Technology (Caltech) and the Jet Propulsion Laboratory (JPL), as a subcontract with the National Aeronautics and Space Administration (NASA). This history would not have come into existence without the entrepreneurial energies of JPL's Nicholas A. Renzetti, who promoted the project and found the money to make it happen. It is also to his credit that he found additional support for a research trip to England and for attendance at a conference in Flagstaff, as well as for the transcription of additional interviews. As JPL technical manager, he administered all technical aspects of the contract. I hope this work meets and exceeds his expectations. During my frequent and sometimes extended visits to JPL, Nick provided secretarial, telephone, photocopying and other supplies and services, as well as a professional environment in which to work. I also want to thank the JPL secretarial personnel, especially Dee Worthington, Letty Rivas, and Judy Hoeptner, as well as Penny McDaniel of the JPL Photo Lab, who was so resourceful in finding pictures.
Teresa L. Alfery, JPL contract negotiator, deserves more than a few words of thanks. Working out the contract details could have been an insufferable experience, were it not for her. Moreover, she continued her cordial and capable performance through several contract modifications.
The contract also came under the purview of the NASA History Office, which provided the author office supplies and services during visits there. More importantly, Chief Historian Roger D. Launius offered encouragement and support in a manner that was both professional and congenial. It was a pleasure to work with Roger. This history owes not inconsequential debt to him and the staff of the History Office, especially Lee Saegesser, archivist, who lent his extensive and unique knowledge of the NASA History Office holdings.
I also want to acknowledge certain individuals who helped along the way. Before this project even began, Joseph N. Tatarewicz afforded it a rich documentary source at the NASA History Office by rescuing the papers of William Brunk, which hold a wealth of information on the Arecibo Observatory and other areas relevant to planetary astronomy at NASA. Joe also was a valuable source of facts and wisdom on the history of the space program and an invaluable guide to the planetary geological community.
This history also owes a debt to Craig B. Waff. His extensive collection of photocopied materials greatly facilitated my research, as did his manuscript histories of the Deep Space Network and Project Galileo. Craig generously offered a place to stay during my first visits to California and was my JPL tour guide.
The staff of the JPL Archives deserves an exceptional word of appreciation. They do not know the word "impossible" and helped facilitate my research in a manner that was always affable and competent. In particular, I want to acknowledge the director, Michael Q. Hooks, for assembling a superb team, John E. Bluth, for his command of the JPL oral history collection and our informative talks about JPL history, and Julie M. Reiz, for her help in expediting access to certain collections.
I also wish to thank those librarians, archivists, historians, and others who expedited my research in, or who provided access to, special documentary collections: Helen Samuels and Elizabeth Andrews, MIT Institute Archives and Special Collections; Mary Murphy, Lincoln Laboratory Library Archives; Ruth Liebowitz, Phillips Laboratory; Richard gingham, Historical Archives, U.S. Army Communications-Electronics Command, Ft. Monmouth, NJ; Richard P. Ingalls and Alan E. E. Rogers, NEROC, Haystack Observatory; George Mazuzan, NSF Historian's File, Office of Legislation and Public Affairs, National Science Foundation; Eugene Bartell, administrative director, National Astronomy and ionosphere Center, Cornell University; Jane Holmquist, Astrophysics and Astronomy Library, Princeton University; and August Molnar, president of the American Hungarian Foundation.
In addition, I want to acknowledge those individuals who made available materials in their possession: Julia Bay, Bryan J. Butler, Donald B. Campbell, Von R. Eshleman, Thomas Gold, Paul E. Green, Jr., Raymond F. Jurgens, Sir Bernard Lovell, Steven J. Ostro, Gordon H. Pettengill, Nicholas A. Renzetti, Martin A. Slade, and William B. Smith. Credit also goes to those individuals who reviewed part or all of this manuscript: Louis Brown, Ronald E. Doel, George S. Downs, John V. Evans, Robert Ferris, Richard M. Goldstein, Paul E. Green, Jr., Roger D. Launius, Sir Bernard Lovell, Steven J. Ostro, Gordon H. Pettengill, Robert Price, Alan E. E. Rogers, Irwin 1. Shapiro, Richard A. Simpson, Martin A. Slade, and Joseph N. Tatarewicz.
There are numerous people at NASA involved in the mechanics of publishing who helped in myriad ways in the preparation of this history. J.D. Hunley, of the NASA History Office, edited and critiqued the text before he departed to take over the History Program at the Dryden Flight Research Center; and his replacement, Stephen J. Garber, helped in the final proofing of the work. Nadine Andreassen of the NASA History Office performed editorial and proofreading work on the project; and the staffs of the NASA Headquarters Library, the Scientific and Technical Information Program, and the NASA Document Services Center provided assistance in locating and preparing for publication the documentary materials in this work. The NASA Headquarters Printing and Design Office developed the layout and handled printing. Specifically, we wish to acknowledge the work of Jane E. Penn, Patricia Lutkenhouse Talbert, Kimberly Jenkins, Lillian Gipson end dames Chi for their design and editorial work. In addition, Michael Crnkovic, Craig A. Larsen, and Larry J. Washington saw the book through the publication process.
Finally, I want to recognize the friendship of fellow cat lover Joel Harris, the cordial and entertaining SETI evening spent at the Griffith Observatory with Mike Klein, Judy Hoeptner, and company (without forgetting the Renaissance Festival!), the stimulating conversations with Adrienne Harris, and the friendly folk dancers of Pasadena, as well as the contra dancers of Highland Park and Franklin Park, and Ghislaine, the most important one of all in many ways.
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Introduction
Planetary radar astronomy has not attracted the same level of public attention as, say, the Apollo or shuttle programs. In fact, few individuals outside those scientific communities concerned with planetary studies are aware of its existence as an ongoing scientific endeavor. Yet, planetary radar has contributed fundamentally and significantly to our knowledge of the solar system.
As early as the 1940s, radar revealed that meteors are part of the solar system. After the first detections of Venus in 1961, radar astronomers refined the value of the astronomical unit, the basic yardstick for measuring the solar system, which the International Astronomical Union adopted in 1964, and they discovered the rotational rate and direction of Venus for the first time. Next, radar astronomers determined the correct orbital period of Mercury and calculated an accurate value for the radius of Venus, a measurement that Soviet and American spacecraft had failed to make reliably. Surprisingly, radar studies of Saturn revealed that its rings were not swarms of minute particles, but rather consisted of icy chunks several centimeters or more in diameter. Planetary radar also provided further proof of Albert Einstein's theory of General Relativity, as well as the "dirty snowball" theory of comets. The only images of Venus' surface available to researchers are those made from radar observations. The ability of planetary radar astronomy to characterize the surfaces of distant bodies has advanced our general knowledge of the topography and geology of the terrestrial planets, the Galilean moons of Jupiter, and the asteroids. The Viking project staff utilized radar data to select potential landing sites on Mars. More recently, radar revealed the surprising presence of ice on Mercury and furnished the first three-dimensional images of an asteroid.
Again, these achievements seldom have attracted the attention of the media. The initial American radar detections of the Moon in 1946 and of Venus in 1961 attracted notice in daily newspapers, weekly news magazines, news reels, and cartoons. Only in recent years have the accomplishments of radar astronomy returned to the front-page of the news. The images of Venus sent back by Magellan received full media coverage, and images of the asteroid Toutatis appeared on the front-page of the New York Times.
Planetary radar astronomy has shared its anonymity with other applications of radar to space research. The NASA radar-equipped SEASAT satellite provided unprecedented images of Earth's oceans; European, Canadian, end Japanese satellites, as well as a number of space shuttles, have imaged Earth with radar. The radars of NASA's Deep Space Network also have played a major role in tracking space launches and spacecraft on route to planets as distant as Saturn and Neptune. Among the more down-to-Earth, visible and even pervasive applications of radar are those for air traffic control and navigation, the surveillance of automobile traffic speeds, and the imaging of weather patterns reported daily on television and radio.
Planetary radar astronomy is part of the great wave of progress in solid-state and digital electronics that has marked the second half of the twentieth century. For instance, the earliest planetary radar experiment marked the first use of a maser (a solid-state microwave amplifying device) outside the laboratory. Although radio astronomy has long claimed the first maser application for itself, namely in April 1958 by Columbia University and the Naval Research Laboratory, two months earlier, MIT's Lincoln Laboratory used a maser in its first attempt to bounce radar waves off Venus. The same radar experiment also saw one of the first uses of a digital tape recorder, as well as the incorporation of a digital computer and other digital data processing equipment into a civilian radar system.
The origins of this solid-state and digital electronics progress, as well as of planetary radar astronomy, are rooted in electronic research and development that started as early as the 1930s. The first radar astronomy experiments, which were carried out on meteors and the Moon in the 1940s, relied on equipment designed and built for military defense during World War II and were based on research conducted during the 1930s.
Planetary radar astronomy, and so too radar itself, had its origins in Big Science. British war preparations during the 1930s concentrated large amounts of scientific, technological, financial, and human resources into a single effort. Part of that effort was a massive radar research and development program that produced an impressive range of defensive and offensive radars. In a secret mission known only at the highest levels of government, Britain gave the United States one of the key devices born of that large-scale radar effort, the magnetron. In turn, the magnetron formed the technological base for an American radar research and development effort on a scale equal to that of the Manhattan Project, which historians traditionally have recognized as the beginning of Big Science.
The history of planetary radar astronomy in the United States is the history of Big Science. Without Big Science, planetary radar astronomy would be impossible and unthinkable. That is one of the main contentions of this book. The radar astronomy experiments of the 1940s and 1950s, as well as much of pre-war radar development, were intimately linked to ionospheric research, which was then undergoing a rapid publication rate typical of Big Science.
Also, the evolutions of planetary radar and radio astronomy converged. The search for research instruments free of military constraints brought planetary radar astronomers closer to radio astronomy during the 1960s, a time when radio astronomy was undergoing a rapid growth that transformed it into Big Science. Planetary radar and radio astronomy shared instruments and a common interest in electronic hardware and techniques, though ironically the instrumentation needs of the two communities ultimately provided little basis for cohabitation.
In the end, military Big Science was far more important than either radio astronomy or ionospheric science. Planetary radar astronomy emerged in the late 1950s thanks to Cold War defense research that furnished the essential instruments of planetary radar experimentation. The vulnerability of the United States to aircraft and ICBM attacks with nuclear explosives necessitated the creation of a network of ever more powerful and sensitive defensive radars. What President Dwight D. Eisenhower called the military-industrial complex, and what historian Stuart Leslie calls the military-industrial-academic complex,1 provided the radar instrument for the first attempts at Venus. The military-industrial or military-industrial-academic complex served as the social matrix which nurtured military and other Big Science research. Planetary radar astronomy eventually found itself part of a different, though at times interlocking, complex centered on the civilian enterprise to explore space, that is, what one might call the NASA-industrial-academic complex.
The emergence of space as Big Science under the financial and institutional aegis of NASA, and the design and construction of a worldwide network of antennas to track launches and communicate with spacecraft, furnished instruments for planetary radar research as early as 1961. Within a decade, NASA became the de facto underwriter of all planetary radar astronomy. Data on the nature of planetary surface features and precise reckoning of both the astronomical unit and planetary orbits were highly valuable to an institution whose primary goal was (and whose budgetary bulk paid for) the designing, building, and launching of vessels for the exploration of the solar system. Association with NASA Big Science enhanced the tendency of radar astronomers to emphasize the utility of their research and promoted mission-oriented, as opposed to basic, research.
The history of planetary radar astronomy is intrinsically interesting and forms the framework of this book. It also says something about Big Science. Defining Big Science, or even Little Science, is not easy though. After all, how true are the images of the Little Scientist as "the lone, long-haired genius, moldering in an attic or basement workshop, despised by society as a nonconformist, existing in a state of near poverty, motivated by the flame burning within him," and the Big Scientist as "honored in Washington, sought after by all the research corporations of the 'Boston ring road,' part of an elite intellectual brotherhood of co-workers, arbiters of political as well as technological destiny"?2
Since the publication in 1963 of Derek J. De Solla Price's ground-breaking Little Science, Big Science, historians have attempted to define Big Science.3 Their considerable efforts have clarified the meaning of the term, though without producing a universally authoritative definition. If large-scale expensive research instruments are the measure, then one might count the island observatory of Tycho Brahe in the sixteenth century, or the giant electrical machines built in eighteenth-century Holland. If Big Science is a large grouping of investigators from several disciplines working together on a common project, then the gathering of mathematicians, chemists, and physicists at Thomas Edison's West Orange laboratory was Big Science. A long-term research project, such as the quest for an AIDS cure, or one that entails elaborate organization, such as the Manhattan Project, might be termed Big Science too.
Defining Big Science is the intellectual equivalent of trying to nail Jell-O to the wall. For the purposes of this book, we shall call Big Science the large-scale organization of science and scientists, underwritten by an imposing pledge of (usually) public funds and centered around a complex scientific instrument. In his search to understand Big Science, Derek Price decided to "turn the tools of science on itself," charting the historical growth of science by means of a variety of statistical indicators obtained from the Institute for Scientific Information in Philadelphia. Price concluded that scientific activity (as measured by the amount of literature published) has grown exponentially over the last three hundred years, doubling in size about every fifteen years.4 We also shall define a rapid growth in scientific literature greater than the Price rate (doubling every fifteen years) as indicating an emerging Big Science field. Whatever it is, Big Science has become the dominant form of contemporary American science. Moreover, because of its scale and scope, the conduct of Big Science necessarily intrudes into many areas of society, and in turn, society, through political, economic, and other activity, shapes the conduct of Big Science.
The interdependency of institutional factors, funding patterns, science, technology, and techniques found in Big Science has been the subject of extensive study by historians and sociologists of science and technology. Scholars traditionally have concerned themselves with both science and technology and their interactions. Such studies came to be termed "internalist," meaning that they dealt solely with the inner workings of science and technology. In contrast stood the so-called "externalist" approaches, which emphasized the social, economic, political, and other factors neglected by the "internalists."
Starting around 1980, sociologists of science, such as Michel Callon, developed new approaches, which were introduced into the history of technology by Thomas P. Hughes. These new approaches came to be called generically the "social construction of technology." The "technosocial networks" of Callon and the "systems" of Hughes consider the "internalist" and "externalist" aspects of technology as constituting a single continuum or "seamless web". Inventors, scientists, instruments, financing, institutions, politics, laws, and so forth are all equally part of the "technosocial network" or "system".5
The chief advantage of replacing the "internalist" and "externalist" dualism with the unitarian approach of the social construction school is the more sophisticated and certainly more complex view of the scientific, technical, economic, political, institutional, legal, and other aspects of Big Science that it offers. Moreover, by stressing that all components of a technosocial network are equal and necessary, the social construction approach dissuades us from emphasizing any one factor, "internal" or "external", over all others.
The social construction approach is useful for creating a taxonomy of the factors that shape Big Science. Nonetheless, although they served as a guiding principle in the writing of this book, social construction case studies do not go far enough; they fail to address the question that is, after chronicling the achievements of radar astronomy, central to this book-namely the conduct of Little Science in the context of Big Science. Furthermore, in all the discussions of Big Science, with few exceptions, the symbiotic relationship between Big Science and Little Science has been overlooked. This relationship is especially relevant to the organization of science within NASA space missions. The scientists who conduct experiments from those spacecraft typify Little Science: they work individually or in small collaborative groups, often with graduate assistants, and have relatively small budgets and limited laboratory equipment. Participation in NASA spacecraft missions induces these Little Scientists to function as part of a Big Science endeavor. The scientists are organized into both working groups around a single scientific instrument and disciplinary groups. They participate in the design of experiments and in the decisions to drop or modify certain experiments, as well as in the design of the instruments themselves. The overall scale of operation and budget is beyond that normally encountered by Little Scientists.
One noteworthy exception to the lack of literature dealing with the relationship between Big Science and Little Science is historian John Krige's study of British nuclear physics research in the period immediately following World War II. The Labor Government of Clement Attlee set out to equip the universities of Birmingham, Glasgow, Liverpool, Cambridge, and Oxford with particle accelerators for conducting high-energy nuclear physics research. The accelerator program involved the kinds of large-scale budgets and instruments that typify Big Science; however, research was conducted in a manner more typical of Little Science. Large multidisciplinary teams, in which physicists and engineers rubbed shoulders, did not form; rather the physicists remained individual academic researchers.6
Krige's case of "Big Equipment but not Big Science" finds its parallel in planetary radar astronomy. Big Science was the sine qua non of planetary radar astronomy, but planetary radar astronomy was not Big Science. It was, and remains, Little Science in terms of manpower, instruments, budget, and publications. Planetary radar astronomy took root within the interstices of Big Science, but rather than expand over time, it actually shrank.
The field attained its largest size, in terms of personnel, instruments, and publications, during the 1960s. Although one can count five active instruments between 1961 and 1964, the greatest number to ever carry out planetary radar experiments, only three subsequently sustained active research programs. That number fell to two instruments after 1975. For much of the period between 1978 and 1986, only one instrument, indeed the only instrument to have an established and secure planetary radar astronomy research program, the Arecibo Observatory, was steadily active.
The number of active planetary radar astronomers has declined since the 1960s too. As a group, they tend not to reproduce as easily or as abundantly as other scientists, and many practitioners in the long run find something else to do. Two paths-artifacts of the field's evolution-lead to a career in planetary radar astronomy. Many follow the traditional university path-doctoral research on a planetary radar topic, followed by a research position that permits them to perform planetary radar experiments. Of the current practitioners, the most recent Ph.D. was granted in 1994, the second most recent in 1978. The path more followed: practitioners were hired to conduct planetary radar experiments.
The declining instrument and manpower numbers are reflected in the planetary radar astronomy publication record (see Appendix: Planetary Radar Astronomy Publications). Price has shown that science publications have doubled about every fifteen years over the last three centuries. The planetary radar publication curve differs markedly from that normal growth pattern, suggesting a ceiling condition that has limited growth. The nature of that ceiling condition, as well as the causal factors for the declining size of the planetary radar enterprise, are part of the story of how planetary radar Little Science has been conducted within the framework of American Big Science. The association of planetary radar Little Science with NASA Big Science ultimately affected the conduct of planetary radar astronomy. Radar astronomers always had argued the utility of their efforts for space research; NASA mission-oriented support of planetary radar astronomy only reinforced that utilitarian inclination. As the story unfolds, other factors that shaped and amplified the utilitarian tendency of radar astronomers will rise to the surface.
Its relationship with NASA Big Science also transformed planetary radar astronomy from an exclusively ground-based scientific activity to one that was conducted in space as well. During the 1960s, planetary radar astronomers distinguished their ground-based research from that conducted from spacecraft, which they characterized as space exploration as opposed to astronomy. Starting in the following decade, when NASA became its sole underwriter, planetary radar astronomy began to engage the planetary geology community largely through its ability to image and otherwise characterize planetary surfaces. NASA funded specific radar imaging projects. At the same time, NASA began planning two missions to Venus, Pioneer Venus and Magellan, in order to capture in radar images the features of that planet's surface. Its opaque atmosphere keeps Venus's surface hidden from sight and bars exploration with optical methods.
Pioneer Venus and Magellan ultimately had a profound impact on the practice of planetary radar astronomy. In addition to enlarging the community of scientists using radar imagery and other data to encompass both geologists and astronomers, those two NASA missions erased the turf boundary between space exploration and ground-based planetary radar astronomy. Although Magellan in particular also gave radar astronomers a taste of Big Science, planetary radar astronomy did not permanently shift from Little to Big Science. Radar imaging from a spacecraft had limited prospects. Ultimately, the greatest consequence of Magellan for planetary radar astronomy was that it effectively ended ground-based radar observations of Venus, the chief object of radar research.
The plan of this book is to relate the history of planetary radar astronomy from its origins in radar to the present day and secondarily to bring to light that history as a case of "Big Equipment but not Big Science". Chapter One sketches the emergence of radar astronomy as an ongoing scientific activity at Jodrell Bank, where radar research revealed that meteors were part of the solar system. The chief Big Science driving early radar astronomy experiments was ionospheric research. Chapter Two links the Cold War and the Space Race to the first radar experiments attempted on planetary targets, while recounting the initial achievements of planetary radar, namely, the refinement of the astronomical unit and the rotational rate and direction of Venus.
Chapter Three discusses early attempts to organize radar astronomy and the efforts at MIT's Lincoln Laboratory, in conjunction with Harvard radio astronomers, to acquire antenna time unfettered by military priorities. Here, the chief Big Science influencing the development of planetary radar astronomy was radio astronomy. Chapter Four spotlights the evolution of planetary radar astronomy at the Jet Propulsion Laboratory, a NASA facility, at Cornell University's Arecibo Observatory, and at Jodrell Bank. A congeries of funding from the military, the National Science Foundation, and finally NASA marked that evolution, which culminated in planetary radar astronomy finding a single Big Science patron, NASA.
Chapter Five analyzes planetary radar astronomy as a science using the theoretical framework provided by philosopher of science Thomas Kuhn. Chapter Six explores the shift in planetary radar astronomy beginning in the 1970s that resulted from its financial and institutional relationship with NASA Big Science. This shift saw the field 1) transform from an exclusively ground-based scientific activity to one conducted in space, as well as on Earth, and 2) capture the interest of planetary scientists from both the astronomy and geology communities. Chapter Seven relates how the Magellan mission was the culmination of this evolution. Chapters Eight and Nine discuss the research carried out at ground-based facilities by this transformed planetary radar astronomy, as well as the upgrading of the Arecibo and Goldstone radars.
The conclusion serves a dual purpose. It responds to the concern for the future of planetary radar astronomy expressed by many of the practitioners interviewed for this book, as well as to the author's wish to provide a slice of applied history that might be of value to both radar astronomers and policy makers. The conclusion also appraises planetary radar as a case of "Big Equipment but not Big Science". It considers the factors that have limited the size of planetary radar, its utilitarian nature, and its dependency on large-scale technological enterprises.
A technical essay appended to this book provides an overview of planetary radar techniques, especially range-Doppler mapping, for the general reader. Furthermore, the text itself explains certain, though not all, technical aspects of radar astronomy. The author assumed that the reader would have a familiarity with general technical and scientific terminology or would have access to a scientific dictionary or encyclopedia. For those readers seeking additional, and especially more technically-oriented, information on planetary radar astronomy, the technical essay includes a list of articles on the topic written by radar practitioners.
Notes
1. Stuart W. Leslie, The Cold War and American Science: The Military-lndustrial-Academic Complex at MIT and Stanford (New York: Columbia University Press, 1993).
2. Derek J. DeSolla Price, Little Science, Big Science... and Beyond (New York: Columbia University Press, 1986), p. 2.
3. Price, Little Science Big, Science... and Beyond, p. 15.
4. Price, Little Science, Big Science (New York: Columbia University Press, 1963). This discussion of Big Science draws on Peter Galison and Bruce Hevly, eds., Big Science: The Growth of Large-Scale Research (Stanford: Stanford University Press, 1992); James H. Capshaw and Karen A. Rader, "Big Science: Price to the Present," Osiris, ser. 2, vol. 7 ( 1992): 3-25; and Joel Genuth, "Microwave Radar, the Atomic Bomb, and the Background to U.S. Research Priorities in World War II," Science, Technology, and Human Values 13 (1988): 276-289.
5. For a discussion of this evolution, see John M. Staudenmaier, "Recent Trends in the History of Technology," The American Historical Review 95 (1990): 715-725, as well as Hughes, "The Seamless Web: Technology, Science, Etcetera, Etcetera," Social Studies of Science 16 (1986): 281-292. The primary social construction works are Wiebe E. Bijker, Hughes, and Trevor Pinch, eds., The Social Construction of Technological Systems: New Directions in the Sociology and History of Technology (Cambridge: MIT Press, 1987), and Bijker and John Law, eds., Shaping Technology/Building Society: Studies in Sociotechnical Change (Cambridge: MIT Press, 1992).
6. John Krige, "The Installation of High-Energy Accelerators in Britain after the War: Big Equipment but not 'Big Science,'" in Michelangelo De Maria, Mario Grilli, and Fabio Sebastiani, eds., The Restructuring of Physical Sciences in Europe and the United States, 1945-1960 (Teaneck, NJ: World Scientific, 1989), pp. 488-501.
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During the 1940s, investigators in the United States and Hungary bounced radar waves off the Moon for the first time, while others made the first systematic radar studies of meteors. These experiments constituted the initial exploration of the solar system with radar. In order to understand the beginnings of radar astronomy, we first must examine the origins of radar in radio, the decisive role of ionospheric research, and the rapid development of radar technology triggered by World War II.
As early as 20 June 1922, in an address to a joint meeting of the Institute of Electrical Engineers and the Institute of Radio Engineers in New York, the radio pioneer Guglielmo Marconi suggested using radio waves to detect ships:1
As was first shown by Hertz, electric waves can be completely reflected by conducting bodies. In some of my tests I have noticed the effects of reflection and deflection of these waves by metallic objects miles away.
It seems to me that it should be possible to design apparatus by means of which a ship could radiate or project a divergent beam of these rays in any desired direction, which rays, if coming across a metallic object, such as another steamer or ship, would be reflected back to a receiver screened from the local transmitter on the sending ship, and thereby immediately reveal the presence and bearing of the other ship in fog or thick weather.
One further advantage of such an arrangement would be that it would be able to give warning of the presence and bearing of ships, even should these ships be unprovided with any kind of radio.
By the time Germany invaded Poland in September 1939 and World War II was underway, radio detection, location, and ranging technologies and techniques were available in Japan, France, Italy, Germany, England, Hungary, Russia, Holland, Canada, and the United States. Radar was not so much an invention, springing from the laboratory bench to the factory floor, but an ongoing adaptation and refinement of radio technology. The apparent emergence of radar in Japan, Europe, and North America more or less at the same time was less a case of simultaneous invention than a consequence of the global nature of radio research.2
Although radar is identified overwhelmingly with World War II, historian Sean S. Swords has argued that the rise of high-performance and long-range aircraft in the late 1930s would have promoted the design of advanced radio navigational aids, including radar, even without a war.3 More decisively, however, ionospheric research propelled radar development in the 1920s and 1930s. As historian Henry Guerlac has pointed out, "Radar was developed by men who were familiar with the ionospheric work. It was a relatively straightforward adaptation for military purposes of a widely-known scientific technique, which explains why this adaptation--the development of radar--took place simultaneously in several different countries."4
The prominence of ionospheric research in the history of radar and later of radar astronomy cannot be ignored. Out of ionospheric research came the essential technology for the beginnings of military radar in Britain, as well as its first radar researchers and research institutions. After the war, as we shall see, ionospheric research also drove the emergence of radar astronomy.
Chain Home
Despite its scientific origins, radar made its mark and was baptized during World War II as an integral and necessary instrument of offensive and defensive warfare. Located on land, at sea, and in the air, radars detected enemy targets and determined their position and range for artillery and aircraft in direct enemy encounters on the battlefield. Other radars identified aircraft to ground bases as friend or foe, while others provided navigational assistance and coastal defense. World War II was the first electronic war, and radar was its prime agent.5
In 1940, nowhere did radar research achieve the same advanced state as in Britain. The British lead initially resulted from a decision to design and build a radar system for coastal defense, while subsequent research led to the invention of the cavity magnetron, which placed Britain in the forefront of microwave radar. The impetus to achieve that lead in radar came from a realization that the island nation was no longer safe from enemy invasion.
For centuries, Britain's insularity and navy protected it from invasion. The advent of long-range airplanes that routinely outperformed their wooden predecessors spelled the end of that protection. Existing aircraft warning methods were ineffectual. That Britain was virtually defenseless against an air assault became clear during the summer air exercises of 1934. In simulated night attacks on London and Coventry, both the Air Ministry and the Houses of Parliament were successfully "destroyed," while few "enemy" bombers were intercepted.6
International politics also had reached a critical point. The Geneva Disarmament Conference had collapsed, and Germany was rearming in defiance of the Treaty of Versailles. Under attack from Winston Churchill and the Tory opposition, the British government abandoned its disarmament policy and initiated a five-year expansion of the Royal Air Force. Simultaneously, the Air Ministry Director of Scientific Research, Henry Egerton Wimperis, created a committee to study air defense methods.
Just before the Committee for the Scientific Survey of Air Defence first met on 28 January 1935, Wimperis contacted fellow Radio Research Board member Robert (later Sir) Watson-Watt. Watson-Watt, who oversaw the Radio Research Station at Slough, was a scientist with twenty years of experience as a government researcher. Ionospheric research had been a principal component of Radio Research Station studies, and Watson-Watt fostered the development there of a pulse-height technique.7
The pulse-height technique was to send short pulses of radio energy toward the ionosphere and to measure the time taken for them to return to Earth. The elapsed travel time of the radio waves gave the apparent height of the ionosphere. Merle A. Tuve, then of Johns Hopkins University, and Gregory Breit of the Carnegie Institution's Department of Terrestrial Magnetism in Washington, first developed the technique in the 1920s and undertook ionospheric research in collaboration with the Naval Research Laboratory and the Radio Corporation of America.8
In response to the wartime situation, Wimperis asked Watson-Watt to determine the practicality of using radio waves as a "death ray." Rather than address the proposed "death ray," Watson-Watt's memorandum reply drew upon his experience in ionospheric research. Years later, Watson-Watt contended, "I regard this Memorandum on the 'Detection and Location of Aircraft by Radio Methods' as marking the birth of radar and as being in fact the invention of radar." Biographer Ronald William Clark has termed the memorandum "the political birth of radar."9 Nonetheless, Watson-Watt's memorandum was really less an invention than a proposal for a new radar application.
The memorandum outlined how a radar system could be put together and made to detect and locate enemy aircraft. The model for that radar system was the same pulse-height technique Watson-Watt had used at Slough. Prior to the memorandum in its final form going before the Committee, Wimperis had arranged for a test of Watson-Watt's idea that airplanes could reflect significant amounts of radio energy, using a BBC transmitter at Daventry. "Thus was the constricting 'red tape' of official niceties slashed by Harry Wimperis, before the Committee for the Scientific Survey of Air Defence had so much as met," Watson-Watt later recounted. The success of the Daventry test shortly led to the authorization of funding (£12,300 for the first year) and the creation of a small research and development project at Orford Ness and Bawdsey Manor that drew upon the expertise of the Slough Radio Research Station.