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Multidisciplinary Use of the J Very Long Baseline Array PE84-16~690 Multidisciplinary Use of the j Very Long Baseline Array Proceedings of a Workshop REPRODUCED BY NATIONAL TECHNICAL NAS INFORMATION SERVICE us DEPAR1MENl OF COMMERCE NAE .. SPRINGFiElD, VA. 22161 10M 50272 ·101 REPORT DOCUMENTATION \1. REPORT NO. PAGE 4. TItle end Subtitle 50 Report Dete Multidisciplinary Use of the Very Long Baseline Array .. Februarv 1984 7. Author(l) L Performln. O...nlutlon Rept. No. 9. Performlna O...nlutlon Neme end Add.... 10. ProJKt/Tuk/Wort! Unit No. National Research Council 11. Contrect(C2 or Gr.nt(G) No. Commission on Physical Sciences, Mathematics, and DMA800-M0366/P Resources ~MDA903-83-M-5896/P i (G)AST-8303119 2101 Constitution Avenue, Washington, DC 20418 ~NA 83AAA02632/P 12. Sponsor1na O..enlutlon Neme end Add_ 11. Type of Report & Period Covered National Science Foundation Final Report. National Aeronautics and Space Administration 11/01/82-3/31/84 Defense Mapping Agency 14. NOAA National Geodetic Survev , Defense Adv. Res. Proj. 15. Supplementer)' Notes . Agency 16. Abltreet (Umlt 200 words) The National Research Council organized a workshop to gather together experts in very long baseline interferometry, astronomy, space navigation, general relativity and the earth sciences,. The purpose of the workshop was to provide a forum for consideration of the various possible multi­ disciplinary uses of the very long baseline array. Geophysical investigations received major attention. Geodesic uses of the very long baseline array were identified as were uses for fundamental astronomy investigations. Numerous specialized uses were identified. i, Document Anelysll e. Descriptors Very Long Baseline Array, astronomical research, space navigation, general relativity, geophysics, earth sciences, geodetic monitoring. b. Identlfie../Open-EMed Terml VLBA, VLA, VCR, GASFET, VLBI, HRAS, MERIT, MARK III, K3, GPS, Gravity Probe-A c. COSATI field/GrouP 1.. lecurft)< CI... (Thll Report) 21. No. of p.... Unclassified 202 Distribution Unlimited 20. Security Cle.. (Thll Pep) 22. Price s.. 'nltrveflonl 011 If.....,.. OPTIONAL FORM 272 (4-77) (Formerly NTIS-55) Dep.rtment of Commerce Multidisciplinary Use ofthe Very Long Baseline Array Proceedings of a Workshop Board on Physics and Astronomy Commission on Physical Sciences, Mathematics, and Resources National Research Council NATIONAL ACADEMY PRESS Washington, D. C. 1983 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Research Council was established by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and of advising the federal government. The Council operates in accordance with general policies determined by the Academy under the authority of its congressional charter of 1863, which establishes the Academy as a private, nonprofit, self-governing membership corporation. The Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in the conduct of their services to the government, the public, and the scientific and engineering communities. It is administered jointly by both Academies and the Institute of Medicine. The National Academy of Engineering and the Institute of Medicine were established in 1964 and 1970, respectively, under the charter of the National Academy of Sciences. This project was sponsored by the National Science Foundation, the National Aeronautics and Space Administration, the Defense Mapping Agency, the NOAA National Geodetic Survey, and the Defense Advanced Research Projects Agency. A limited number of copies are available from Board on Physics and Astronomy National Academy of Sciences 2101 Constitution Avenue, N.W. Washington, D.C. 20418 ORGANIZING COMMITTEE FOR THE WORKSHOP ON MULTIDISCIPLINARY USES OF THE VERY LONG BASELINE ARRAY BERNARD F. BURKE, Massachusetts Institute of Technology, Chairman WILLIAM E. CARTER, National Geodetic Survey THOMAS CLARK, Goddard Space Flight Center MARSRqLL H. COHEN, California Institute of Technology KE:mETH J. JOHNSTON, Naval Research Laboratory KENNETH I. KELLERMAN, National Radio Astronomy Observatory NICHOLAS A. RENZETTI, California Institute of Technology IRWIN SHAPIRO, Harvard University GART WESTERHOUT, U.S. Naval Observatory DONALD C. SHAPERO, Staff Officer iii BOARD ON PHYSICS AND ASTRONOMY HANS FRAUENFELDER, University of Illinois, Chairman FELIX H. BOEHM, California Institute of Technology RICHARD C. BREWER, IBM San Jose Research Laboratory DEAN E. EASTMAN, IBM T.J. Watson Research Center SANDRA M. FABER, University of California, Santa Cruz JAMES E. GUNN, Princeton University LEO P. KADANOFF, University of Chicago W. CARL LINEBERGER, University of Colorad NORMAN RAMSEY, University of virginia MARSHALL N. ROSENBLUTH, University of Texas WILLIAM P. SLICHTER, Bell Laboratories SAM B. TRElMAN, Princeton University DONALD C. SHAPERO, Staff Director iv COMMISSION ON PHYSICAL SCIENCES, MATHEMATICS, AND RESOURCES HERBERT FRIEDMAN, National Research Council, Chairman ELKAN R. BLOUT, Harvard Medical School WILLIAM BROWDER, Princeton University BERNARD F. BURKE, Massachusetts Institute of Technology HERMAN CHERNOFF, Massachusetts Institute of Technology MILDRED S. DRESSELHAUS, Massachusetts Institute of Technology WALTER R. ECKELMANN, Sohio Petroleum Company JOSEPH L. FISHER, Office of the Governor, Commonwealth of Virginia JAMES C. FLETCHER, University of Pittsburgh WILLIAM A. FOWLER, California Institute of Technology GERHART FRIEDLANDER, Brookhaven National Laboratory EDWARD A. FRIEMAN, Science Applications, Inc. EDWARD D. GOLDBERG, Scripps Institution of Oceanography CHARLES L. HOSLER, JR., pennsylvania State University KONRAD B. KRAUSKOPF, Stanford University CHARLES J. MANKIN, Oklahoma Geological Survey WALTER H. MUNK, University of California, San Diego GEORGE E. PAKE, Xerox Research Center ROBERT E. SIEVERS, University of Colorado HOWARD E. SIMMONS, JR., E.I. du Pont de Nemours & Co., Inc. JOHN D. SPENGLER, Harvard School of public Health HATTEN S. YODER, JR., Carnegie Institution of Washington RAPHAEL G. KASPER, Executive Director v CONTENTS 1 INTRODUCTION AND SUMMARY 1 2 PURPOSE OF THE WORKSHOP 7 Bernard F. Burke 3 SPECIAL PRESENTATION 8 George Keyworth PART I. THE PROPOSED VERY LONG BASELINE ARRAY 18 4 THE VLBA: SCIENTIFIC, TECHNICAL, AND PLANNING OVERVIEW 20 Kenneth I. Kellermann 5 SPECTRAL LINE STUDIES WITH A VLBA 25 Mark J. Reid 6 ASTROPHYSICAL OBJECTIVES 34 Marshall H. Cohen PART II. GEODESY 37 7 GEOPHYSICAL REASONS FOR MONITORING CONTEMPORARY PLATE MOTIONS AND THE EARTH'S ROTATION 39 Peter L. Bender 8 POLAR MOTION AND EARTH ROTATION 44 William E. Carter 9 USING THE VLBA FOR OBTAINING EARTH ROTATION PARAMETERS 52 J.H. Spencer 10 CONTRIBUTIONS OF THE VLBA TO OPERATIONS AT THE U.S. NAVAL OBSERVATORY 59 Dennis McCarthy 11 THE CRUSTAL DYNAMICS PROJECT 64 Robert J. Coates vii 12 MEASUREMENTS OF CRUSTAL MOTION 72 Thomas Clark PART IIIe ASTROMETRY 79 13 OVERVIEW OF ASTROMETRIC PROBLEMS 81 Gart Westerhout 14 TOWARD THE DEFINITION OF AN INERTIAL REFERENCE FRAME 84 Kenneth J. Johnston 15 ASTRONOMICAL CONSTANTS AND THE VLBA 92 Jay H. Lieske 16 IMPLICATIONS OF VLBA MEASUREMENT FOR EPHEMERIDES 102 P. Kenneth Seidelmann 17 GENERAL RELATIVITY AND THE VLBA III Edward B. Fomalont PART IV. OTHER USERS 117 18 GENERAL VLBA CONSIDERATIONS 119 Alan E.E. Rogers 19 USES OF THE VLBA RELATED TO DEEP-SPACE NAVIGATION 125 Arthur E. Niell 20 A VLBI OBSERVATORY IN SPACE--AN ENHANCEMENT OF THE VLBA 132 R.A. Preston 21 PRECISE SATELLITE TRACKING 145 Charles Counselman 22 DEFINITION OF THE U.S. GEODETIC GRID 152 William Strange 23 CLOCK SYNCHRONIZATION CAPABILITIES OF THE VLBA 158 W.J. Klepczynski PART V. CONCLUSION 165 24 GENERAL DISCUSSION 167 25 SUMMARY AND CONCLUSIONS 187 Bernard F. Burke APPENDIXES 191 A AGENDA FOR THE WORKSHOP ON MULTIDISCIPLINARY USES OF THE VLBA 193 B LIST OF INVITEES TO THE WORKSHOP ON MULTIDISCIPLINARY USES OF THE VLBA 195 viii 1 INTRODUCTION AND SUMMARY BACKGROUND The recently released report of the National Research Council's Astronomy Survey Committee recommends construction of an array of 10 radio telescopes situated over the continental united States, Hawaii, and Alaska. The Very Long Baseline Array (VLBA), as it is known in the astronomy community, would have as its principal scientific objective the observation with very high angular resolution of distant radio­ emitting celestial objects such as quasars. In addition to providing an extremely accurate fix on the position of the objects, such high angular resolution would make possible the observation of the fine detail of their internal structure and dynamics. Such high resolution can be accomplished by synchronizing 10 widely spaced antennas, the radio frequency signals of which are synchronized with extremely precise timing signals provided by atomic clocks. The signals are then combined with the aid of computer processing to yield
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