NASA NASA-TP-2244 198400141l0 Technical Paper ...... 2244 January 1984 SETI Science ), Working Group Report • . ... ..... " t " " - 5 "_('n N/ A ! ERRATA NASA Technical Paper 2244 SETI ScienceWorkingGroup Report Edited by Frank Drake, John H.Wolfe, and Charles L. Seeger October 1983 Title page: Words "Edited by" to precede list of names Page 54: Equation (3) should read = s2 + 2sn + n2 Page 56: Equation (30) should read s(t) = [A + a(t)] cos o_t+ b(t)sin _ot Page 59: Second line aboveequation (60a) should read and if we let x = x/Tcos 0, and y = x/7 sin 0, then the result Page 60: Line above equation (62) should read For r << 1, p(O)_ [1/(2n)] [1 + x/'ff7cos O] so that Page 63: Last line of paragraph ending after equation 81 should read (sin _i/_)flo(5 - 3')as a function of _ when 7 = 7r/2. First line of followingparagraph should read Although we have not proved it generally,we have COSATIpage: Item 7 should include John H. Wolfe's affiliation: (Ames Research Center, Moffett Field, Calif.) Issued 4-4-84 I j" NASA 3117o614s31314 Technical Paper 2244 1984 SETI Science Working Group Report Frank Drake Cornell University Ithaca, New York John H. Wolfe Ames Research Center Moffett Field, California Charles L. Seeger San FranciscoState University San Francisco,California NI SA National Aeronautics and Space Administration Scientific and Technical Information Office 1984 TABLE OF CONTENTS Page FOREWORD ......................................................................... v PREFACE ........................................................................... vii BACKGROUND....................................................................... ix THE SETI SCIENCE WORKING GROUP .................................................... xi SSWGMembership .................................................................. xi Additional Participants ............................................................... xii SSWGMeetings .................................................................... xm Conclusions and Recommendations ....................................................... xm GLOSSARY ......................................................................... xv EXECUTIVE SUMMARY ................................................................ xvii INTRODUCTION ...................................................................... xix CHAPTER 1: FUNDAMENTAL CONCEPTS OF MICROWAVESEARCHES FOR EXTRATERRESTRIAL INTELLIGENCE .......................................... 1 CHAPTER 2: GENERAL SEARCH STRATEGY ............................................... 7 CHAPTER 3: DETAILED SEARCH STRATEGY .............................................. 11 CHAPTER 4: THE SETI EXPERIMENTAL PROGRAM.......................................... 19 CHAPTER 5: THE PROTOTYPE SETI INSTRUMENTATION ..................................... 25 CHAPTER 6: POTENTIAL ASTRONOMICAL RESULTS FROM THE SETI PROGRAM AND ITS EQUIPMENT ......................................... 35 CHAPTER 7: SCIENTIFIC COMMUNITYINTERACTION WITH THE SETI PROGRAM .................. 39 APPENDIX A: CONCEPTS SUPPORTING MICROWAVESEARCHES AS THE PREFERRED APPROACH TO SETI ............................................ 41 B. M. Oliver APPENDIX B: THE MULTICHANNEL SPECTRUMANALYZER ................................... 43 A. M. Peterson and K. S. Chen APPENDIX C: SIGNAL RECOGNITION .................................................... 49 D. Kent Cullers,BernardM. Oliver,John R. Day, and Edward T. Olsen APPENDIX D: ESTIMATES OF THE RELATIVE PROBABILITY OF SUCCESS OF THE SETI SEARCH PROGRAM ............................................ 67 Frank D. Drake APPENDIX E: ANTENNA FEEDS FOR THE ARECIBO TELESCOPE............................... 71 Frank D. Drake andMichaelM. Davis ffi Page APPENDIX F: THE RADIO FREQUENCY INTERFERENCE PROBLEM ............................. 75 Woodruff T. Sullivan, 111 APPENDIX G: DATA ARCHIVES ......................................................... 77 Woodruff T. Sullivan, III APPENDIX H: SPECTRAL LINE STUDIES USING SETI INSTRUMENTATION ........................ 79 B. Zuckerman APPENDIX I: HI AND H20 SURVEYS .................................................... 85 GillianR. Knapp APPENDIX J: POTENTIAL USE OF SETI INSTRUMENTATION IN PULSAR RADIO ASTRONOMY ...................................................... 87 1vanR. Linscott APPENDIX K: SETI AND SERENDIPITY ................................................... 91 Jill Tarter APPENDIX L: THE ADVANTAGES OF COHERENT TELESCOPE ARRAYS FOR SETI ................. 95 WilliamJ. Welch APPENDIX M: ON THE OPTIMUM FREQUENCY FOR INTERSTELLARCOMMUNICATIONS: CENTIMETER VERSUS MILLIMETER VERSUS INFRARED WAVELENGTHS ............. 99 B. Zuckerman SELECTED SETI REFERENCES AND READING LIST ......................................... 101 Commentary by CharlesL. Seeger iv FOREWORD The detection and study of other civilizations in space is Having seen a way to achieve the desired instrumenta- one of the most tantalizing and potentially rewarding enter- tion, it is possible to design a detailed observing program, and prises open to contemporary society. It is possible that intel- it is given here. This very general program calls for searching ligent and technological life can occur elsewhere in space; selected nearby regions for weak signals and the entire sky indeed, most would say it was very probable, although some for stronger signals. Thus we not only address the possibility argue for a paucity of intelligent life in the cosmos. The con- that most civilizations have radio transmitters no more templation of other civilizations must be, for the time being, powerful than our own, but also the possibility that there are very much an experimental science. Only after much study perhaps a few civilizations which transmit particularly strong may the subject become the grist for hard theorizing. For- signals. The program calls for the development of unusually tunately, we now have instruments which can make meaning- sensitive computational procedures which can search the data ful searches for other civilizations, and conduct such searches collected by our radio telescopes for many forms of radio at a cost that is extremely modest. We believe that it is time signals. Together, the observational and analytic programs to proceed with serious efforts to detect the existence of create an overall cosmic search which is vastly more thorough other intelligent beings in space, than the sum of all previous searches. And the cost is This subject is not new. There have been two major reasonable and realistic. studies in the last decade, both concluding that it is timely For one fundamental reason it is important that the pro- and promising to conduct a search for other civilizations by grams described here begin at the very earliest possible time. testing for the presence of short-wavelength radio transmis- Each passing day sees the radio brightness of our own civili- sions from them. In the present plan, as described in this zation take another leap in intensity, further increasing the report, this same approach has been favored. What has greatest technical obstacle to searching for faint signals from changed is our technology. In the 10 years since the original the depths of space. Many of the loud signals of Earth studies, which produced the seminal Project Cyclops report, unavoidably enter our instruments, blanking out parts of the data processing technology has improved enormously. This is spectrum and, in other parts, causing confusion, wasted of the utmost importance to SETI, for it has long been effort, and delay. Any substantial delay in the SETI search recognized that our greatest weakness in searching the could quite possibly decrease the prospects for success so "cosmic haystack" for radio signals may not be, after all, the greatly that the potential chances for success could be size of our telescopes or the sensitivity of our radio receivers, restored only through such heroic measures as observing but rather our ability to sort through the immensity of the from deep in space, shielded from the Earth by a natural or radio spectrum. Now it is possible, artificial body. Thus in this, the third major effort to study the prob- lem, the last requirement for a viable SETI program is satis- Frank D. Drake fled. A versatile and powerful radio spectrum analyzer is Goldwin Smith Professor of Astronomy designed which offers the ability, at last, to search the radio Cornell University spectrum in a thorough and timely manner. Ithaca, New York v PREFACE In the summer of 1970, a small group of scientists at the was formed, under the chairmanship of John Wolfeof Ames NASA Ames Research Center met to discusstwo provocative and Sam Gulkis of JPL. Details of the mandate and member- questions. First, is there a valid scientific basis for the suppo- ship of the Group are givenin pagesthat follow. sition that intelligent life may be widely distributed in the This document is the first report of the SSWG. Universe? Second, do we now havethe technological capabil- A very considerable amount of work has gone into this ity to detect the existence of extraterrestrial intelligent life? volume. I must acknowledge the leading roles played by the The group concluded that the answer to both questions was editors Frank Drake of Cornell University, John Wolfe of "yes," and they recommended intensive studies of both Ames Research Center, and Charles Seeger of San Francisco questions. State University. Sam Gulkis and his colleagues at JPL have Over the next 10 years a variety of studies were carried made significant