/ 11/¸' --_ S NASA SP-4218 TO SEE THE UNSEEN A History of Planetary Radar Astronomy by AndrewJ. Butrica The NASA History Series National Aeronautics and Space Administration NASA History Office Washington, D.C. 1996 Library of Congress Cataloguing-in-Publication Data Tt_ See the Unseen: A History of Planetary Radar Astr_nomy / AndrewJ. Butrica p. cm.--(The NASA history series) (NASA SP: 4218) Includes bibliographical re|erences and indexes. 1, Planetology--United States. 2. Planet._---Explor-ation. 3. Radar in Astrom_my, I. Title. I1. Selies. IlL Series: NASA SP: 4218. QB602.9.B/47 1996 95-358_1 523.2'028-dc20 CIP 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, lrina and Dmitry Gouzevitch, Anna Guagnini, Andreas Kahlow, Stephan Lindner,, Michael Osborne, Anne Rasmussen, Mari Williams, Anna Pusztai, and above all Robert Fox. Contents Acknowledgments ....................................................... iii Introduction ........................................................... vii Chapter One: A Meteoric Start ............................................ 1 Chapter Two: Fickle Venus ............................................... 27 Chapter Three: Storm und Drang ......................................... 55 Chapter Four: Little Science/Big Scicnce ................................... 87 Chapter Five: Normal Science ........................................... 117 Chapter Six: Pioneering on Venus and Mars ................................ 149 Chapter Seven: Magellan ............................................... 177 Chapter Eight: The Outer Limits ......................................... 205 Chapter Nine: One Step Beyond ......................................... 225 Conclusion: W(h)ither Planetary Radar Astronomy? .......................... 259 Planetary Radar Astronomy Publications ................................... 267 A Note on Sources ..................................................... 269 Interviews ........................................................... 271 Technical Essay: Planetary Radar Astronomy ................................ 275 Abbreviations ......................................................... 287 Index ............................................................... 289 About the Author ...................................................... 297 The NASA History Series ............................................... 299 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 fiU 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 nations' 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 long_ 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; Lye, 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) ii Acknowledgments 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, how- ever; 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 fre- quency, 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 acdvity has changed over dme, 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 subcon- tract 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 atten- dance 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 theJPL 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. iii 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 profes- sional and congenial. It was a pleasure to work with Roger. This history owes not inconse- quential 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 pro- ject 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 informa- tion 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 pro- gram 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 myJPL 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 theJPL oral his- tory collection and our informative talks aboutJPL history, andJulie 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 Bingham, Historical Archives, U.S. Army Communications-Electronics Command, Ft. Monmouth, NJ; Richard P. Ingalls and Alan