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Radiation and the International Space Station: Recommendations to Reduce Risk Radiation and the International Space Station Recommendations to Reduce Risk Committee on Solar and Space Physics Committee on Solar-Terrestrial Research Space Studies Board Board on Atmospheric Sciences and Climate Commission on Physical Sciences, Mathematics, and Applications Commission on Geosciences, Environment, and Resources National Research Council NATIONAL ACADEMY PRESS Washington, D.C.
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Radiation and the International Space Station: Recommendations to Reduce Risk 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 committees responsible for the report were chosen for their special competences and with regard for appropriate balance. Support for this project was provided by Contract NASW 96013 between the National Academy of Sciences and the National Aeronautics and Space Administration. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsor. Cover: Ground track of ISS orbits superposed on a globe along with polar cap areas (shown in yellow), where multimega-electron volt solar energetic particles penetrated to low altitudes during an SPE in November 1997. (Image courtesy of R.A. Leske, R.A. Mewaldt, E.C. Stone, and T.T. von Rosenvinge, “Geomagnetic Cutoff Variations During Solar Energetic Particle Events—Implications for the Space Station,” Proceedings of the 25th International Cosmic Ray Conference, 2, Space Research Unit, Department of Physics, Potchefstroom University for Christian Higher Education, South Africa, 1997, p. 381.) International Standard Book Number 0-309-06885-1 Copies of this report are available free of charge from: Space Studies Board National Research Council 2101 Constitution Avenue, NW Washington, DC 20418 Copyright 2000 by the National Academy of Sciences. All rights reserved. Printed in the United States of America
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Radiation and the International Space Station: Recommendations to Reduce Risk THE NATIONAL ACADEMIES National Academy of Sciences National Academy of Engineering Institute of Medicine National Research Council The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. William A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized 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 advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. William A. Wulf are chairman and vice chairman, respectively, of the National Research Council.
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Radiation and the International Space Station: Recommendations to Reduce Risk COMMITTEE ON SOLAR AND SPACE PHYSICS GEORGE L. SISCOE, Boston University, Chair CHARLES W. CARLSON, University of California, Berkeley ROBERT L. CAROVILLANO, Boston College TAMAS I. GOMBOSI, University of Michigan RAYMOND A. GREENWALD, Applied Physics Laboratory JUDITH T. KARPEN, Naval Research Laboratory GLENN M. MASON, University of Maryland MARGARET A. SHEA, Air Force Research Laboratory KEITH T. STRONG, Lockheed Palo Alto Research Center RICHARD A. WOLF, Rice University ARTHUR CHARO, Senior Program Officer RONALD TURNER, Consultant CARMELA J. CHAMBERLAIN, Senior Project Assistant (through March 1999) THERESA M. FISHER, Senior Project Assistant (from April 1999)
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Radiation and the International Space Station: Recommendations to Reduce Risk COMMITTEE ON SOLAR-TERRESTRIAL RESEARCH MICHAEL C. KELLEY, Cornell University, Chair MAURA E. HAGEN, National Center for Atmospheric Research MARY K. HUDSON, Dartmouth College NORMAN F. NESS, Bartol Research Institute THOMAS F. TASCIONE, Sterling Software ELBERT (JOE) FRIDAY, JR., Director, Board on Atmospheric Sciences and Climate TENECIA A. BROWN, Senior Project Assistant
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Radiation and the International Space Station: Recommendations to Reduce Risk SPACE STUDIES BOARD CLAUDE R. CANIZARES, Massachusetts Institute of Technology, Chair MARK R. ABBOTT, Oregon State University FRAN BAGENAL, University of Colorado DANIEL N. BAKER, University of Colorado ROBERT E. CLELAND, University of Washington GERARD W. ELVERUM, JR., TRW Space and Technology Group* MARILYN L. FOGEL, Carnegie Institution of Washington BILL GREEN, Former Member, U.S. House of Representatives JOHN H. HOPPS, JR., Morehouse College CHRIS J. JOHANNSEN, Purdue University ANDREW H. KNOLL, Harvard University* RICHARD G. KRON, University of Chicago JONATHAN I. LUNINE, University of Arizona ROBERTA BALSTAD MILLER, CIESIN-Columbia University GARY J. OLSEN, University of Illinois, Urbana-Champaign MARY JANE OSBORN, University of Connecticut Health Center GEORGE A. PAULIKAS, The Aerospace Corporation JOYCE E. PENNER, University of Michigan THOMAS A. PRINCE, California Institute of Technology PEDRO L. RUSTAN, JR., Ellipso, Inc. GEORGE L. SISCOE, Boston University EUGENE B. SKOLNIKOFF, Massachusetts Institute of Technology MITCHELL SOGIN, Marine Biological Laboratory NORMAN E. THAGARD, Florida State University ALAN M. TITLE, Lockheed Martin Advanced Technology Center RAYMOND VISKANTA, Purdue University PETER VOORHEES, Northwestern University JOHN A. WOOD, Harvard-Smithsonian Center for Astrophysics JOSEPH K. ALEXANDER, Director * Former member.
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Radiation and the International Space Station: Recommendations to Reduce Risk BOARD ON ATMOSPHERIC SCIENCES AND CLIMATE ERIC J. BARRON, Pennsylvania State University, Co-chair JAMES R. MAHONEY, International Technology Corporation, Co-chair SUSAN K. AVERY, University of Colorado LANCE F. BOSART, State University of New York at Albany MARVIN A. GELLER, State University of New York at Stony Brook DONALD M. HUNTEN, University of Arizona* JOHN IMBRIE, International Technology Corporation* CHARLES E. KOLB, Aerodyne Research, Inc. THOMAS J. LENNON, Brig. Gen. USAF (ret.), WSI Corp.* ROGER A. PIELKE, JR., National Center for Atmospheric Research ROBERT T. RYAN, WRC-TV MARK R. SCHOEBERL, NASA Goddard Space Flight Center JOANNE SIMPSON, NASA Goddard Space Flight Center NIEN DAK SZE, Atmospheric and Environmental Research, Inc. ROBERT WELLER, Woods Hole Oceanographic Institution ERIC F. WOOD, Princeton University ELBERT (JOE) FRIDAY, JR., Director * Former member.
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Radiation and the International Space Station: Recommendations to Reduce Risk COMMISSION ON PHYSICAL SCIENCES, MATHEMATICS, AND APPLICATIONS PETER M. BANKS, Veridian ERIM International, Inc., Co-chair W. CARL LINEBERGER, University of Colorado, Co-chair WILLIAM F. BALLHAUS, JR., Lockheed Martin Corp. SHIRLEY CHIANG, University of California at Davis MARSHALL H. COHEN, California Institute of Technology RONALD G. DOUGLAS, Texas A&M University SAMUEL H. FULLER, Analog Devices, Inc. JERRY P. GOLLUB, Haverford College MICHAEL F. GOODCHILD, University of California at Santa Barbara MARTHA P. HAYNES, Cornell University WESLEY T. HUNTRESS, JR., Carnegie Institution CAROL M. JANTZEN, Westinghouse Savannah River Company PAUL G. KAMINSKI, Technovation, Inc. KENNETH H. KELLER, University of Minnesota JOHN R. KREICK, Sanders, a Lockheed Martin Company (ret.) MARSHA I. LESTER, University of Pennsylvania DUSA M. McDUFF, State University of New York at Stony Brook JANET L. NORWOOD, U.S. Commissioner of Labor Statistics (ret.) M. ELISABETH PATÉ-CORNELL, Stanford University NICHOLAS P. SAMIOS, Brookhaven National Laboratory ROBERT J. SPINRAD, Xerox PARC (ret.) NORMAN METZGER, Executive Director (through July 1999) MYRON F. UMAN, Acting Executive Director (from August 1999)
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Radiation and the International Space Station: Recommendations to Reduce Risk COMMISSION ON GEOSCIENCES, ENVIRONMENT, AND RESOURCES GEORGE M. HORNBERGER, University of Virginia, Chair RICHARD A. CONWAY, Union Carbide Corporation (ret.) THOMAS E. GRAEDEL, Yale University THOMAS J. GRAFF, Environmental Defense Fund EUGENIA KALNAY, University of Maryland DEBRA KNOPMAN, Progressive Policy Institute KAI N. LEE, Williams College RICHARD A. MESERVE, Covington & Burling RADM. JOHN B. MOONEY, JR., USN (ret.), J. Brad Mooney Associates, Ltd. HUGH C. MORRIS, El Dorado Gold Corporation, Vancouver, British Columbia H. RONALD PULLIAM, University of Georgia MILTON RUSSELL, University of Tennessee THOMAS C. SCHELLING, University of Maryland ANDREW R. SOLOW, Woods Hole Oceanographic Institution VICTORIA J. TSCHINKEL, Landers and Parsons E-AN ZEN, University of Maryland MARY LOU ZOBACK, U.S. Geological Survey ROBERT M. HAMILTON, Executive Director
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Radiation and the International Space Station: Recommendations to Reduce Risk Foreword A major objective of the International Space Station is learning how to cope with the inherent risks of human spaceflight—how to live and work in space for extended periods. The construction of the station itself provides the first opportunity for doing so. Prominent among the challenges associated with ISS construction is the large amount of time that astronauts will be spending doing extravehicular activity (EVA), or ''space walks." EVAs from the space shuttle have been extraordinarily successful, most notably the on-orbit repair of the Hubble Space Telescope. But the number of hours of EVA for ISS construction exceeds that of the Hubble repair mission by orders of magnitude. Furthermore, the ISS orbit has nearly twice the inclination to Earth's equator as Hubble's orbit, so it spends part of every 90-minute circumnavigation at high latitudes, where Earth's magnetic field is less effective at shielding impinging radiation. This means that astronauts sweeping through these regions will be considerably more vulnerable to dangerous doses of energetic particles from a sudden solar eruption. This putative radiation danger prompted the present study. It applies what we have learned from past investigations of solar emanations and their effects on Earth's magnetosphere to assess the risk and find ways to minimize it. The study estimates that the likelihood of having a potentially dangerous solar event during an EVA is indeed very high. It also recommends steps that can be taken immediately, and over the next several years, to provide adequate warning so that the astronauts can be directed to take protective cover inside the ISS or shuttle. The near-term actions include programmatic and operational ways to take advantage of the multiagency assets that currently monitor and forecast space weather, and ways to improve the in situ measurements and the predictive power of current models. The radiation risk is real, but it is also very susceptible to management. That there have been no known overexposures to date is due partly to such good management. Now it is time to revise the protocols and practices of the past to encompass the new challenges of ISS construction and permanent habitation to ensure that this good record continues in the future. Claude R. Canizares, Chair Space Studies Board
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Radiation and the International Space Station: Recommendations to Reduce Risk Acknowledgments Preparing this report would not have been possible without the help of the many individuals who provided the Committee on Solar and Space Physics and the Committee on Solar-Terrestrial Research (CSSP/CSTR) with presentations, consultations, and written materials. The committees are especially grateful to the following individuals: for information on the probability of a solar particle event (SPE) coinciding with an International Space Station (ISS) construction mission, Ronald Turner (ANSER Corporation); for information on the properties of penetrating radiation and on the latitudinal cutoff of SPE particles, Don Smart (Air Force Research Laboratory, ret.); for information on the properties and measurements of highly relativistic electrons in the outer radiation belt, Herbert Kroehl (NOAA's National Geophysics Data Center) and Bernard Blake (Aerospace Corporation); for information pertaining to NOAA's Space Environment Center (SEC), Gary Heckman (NOAA-SEC); for information on matters pertaining to mission operations at Johnson Space Center (JSC) and on radiation data taken on Mir and the shuttles, Michael Golightly and Gautam Badhwar (both at JSC); and for information pertaining to radiation risk management during the Apollo era (the SPAN program), Donald Robbins, Alva Hardy, and Rod Rose (all at JSC during the Apollo era). In addition, CSSP/CSTR wishes to acknowledge the following individuals for informative presentations and interviews at its meetings: for a flight director's perspective, Paul Hill (JSC); for a flight surgeon's perspective, Jeff Jones (JSC); for an astronaut's perspective, Norman Thagard (Florida State University); for information on radiation effects on biological materials and organisms and on research programs pertaining to these, Walter Schimmerling (NASA headquarters), Richard Setlow (Brookhaven National Laboratory), R.J. Michael Fry (Oak Ridge National Laboratory), and Larry Townsend (University of Tennessee); and for information on radiation effects on other than biological materials and on NASA's Space Environment Effects program at Marshall Space Flight Center, Dana Brewer (NASA headquarters) and Janet Barth (Goddard Space Flight Center). The report has also benefited from inputs by members of the National Research Council's Committee on Space Biology and Medicine, which is chaired by Mary J. Osborn; from the Space Studies Board, especially Fran Bagenal; and from Margaret Kivelson, liaison from the Commission on Physical Sciences, Mathematics and Applications to the Space Studies Board. This report has been reviewed by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the Report Review Committee of the National Research Council (NRC). The purpose of this independent review is to provide candid and critical comments that will assist the authors and the NRC in making the published report as sound as possible and to ensure that the report meets institutional
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Radiation and the International Space Station: Recommendations to Reduce Risk standards for objectivity, evidence, and responsiveness to the study charge. The contents of the review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. CSSP/CSTR wishes to thank the following individuals for their participation in the review of this report: J. Bernard Blake, the Aerospace Corporation; Joan Feynman, Jet Propulsion Laboratory; R.J. Michael Fry, Oak Ridge National Laboratory; John Grunsfeld, NASA Johnson Space Center; Louis J. Lanzerotti, Lucent Technologies; Edward T. Lu, NASA Johnson Space Center; Frank B. McDonald, University of Maryland; and Donald J. Williams, Johns Hopkins University Applied Physics Laboratory. Although the individuals listed above have provided many constructive comments and suggestions, responsibility for the final content of this report rests solely with CSSP/CSTR and the NRC.
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Radiation and the International Space Station: Recommendations to Reduce Risk Contents EXECUTIVE SUMMARY 1 1 SCOPING THE PROBLEM 7 1.1 Radiation in Space 7 1.2 Space Weather Context 10 1.3 Metrics of Radiation Risk 11 1.4 Radiation and the International Space Station 12 1.5 Issues in Managing Radiation Risk During ISS Construction 18 1.6 The Apollo Experience 19 1.7 Summary and Recommendation 20 1.8 Notes and References 21 2 SOLAR PARTICLE EVENTS AND THE INTERNATIONAL SPACE STATION 24 2.1 Background to an Assessment of SPE Impacts on ISS Construction 24 2.2 Probability of SPE Impact on ISS Construction 25 2.3 Correlation between SPEs and Size of the SPE Zone 27 2.4 Summary and Recommendation 30 2.5 Notes and References 30 3 RELATIVISTIC ELECTRONS AND THE INTERNATIONAL SPACE STATION 32 3.1 Outer Belt Electrons 32 3.2 Monitoring Outer Belt Electrons 33 3.3 Predictability of Radiation Belt Electrons at Low Altitude 34 3.4 Assessment of Hazards Faced by Astronauts during ISS Construction 35 3.5 Operational Strategy 36 3.6 Summary and Recommendations 37 3.7 Notes and References 38
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Radiation and the International Space Station: Recommendations to Reduce Risk 4 SPACECRAFT SOURCES OF OPERATIONAL RADIATION DATA 39 4.1 Value of Spacecraft Monitors in Support of ISS Construction 39 4.2 An Interagency Fleet of Spacecraft Monitors 41 4.3 Future Spacecraft in Support of ISS Operations 42 4.4 Summary and Recommendation 44 4.5 Notes and References 44 5 INTERAGENCY CONNECTIONS 45 5.1 Institutional Factors Limiting Interagency Ability to Provide Better Information for Operational Radiation Risk Assessments 45 5.2 Recommendations 47 6 INTRA-NASA CONNECTIONS 48 6.1 Radiation: A Concern throughout NASA 48 6.2 NASA Programs That Involve Radiation 49 6.3 Communication between Programs with an Interest in Radiation 50 6.4 Summary and Recommendation 51 EPILOGUE: A NOTIONAL SCENARIO FOR IMPROVED SUPPORT OF INTERNATIONAL SPACE STATION CONSTRUCTION 52 E.1 Vision of an ISS Construction Mission Supported by Reliable, Accurate Radiation Forecast Models during the Solar Maximum 52 E.2 The Way Things Ought to Work 52 E.3 The Missing Pieces 55 E.4 Timetable for Implementing the Report's Recommendations 55 APPENDIXES A SPACE WEATHER MODELS APPLIED TO RADIATION RISK REDUCTION 59 A.1 Space Weather Models 59 A.2 Near-Earth Space Environment Models 61 A.3 Advanced Empirically Based Forecast Models of Radiation Risk Parameters 62 A.4 Observational Supplements to Model-Based Forecasts 62 A.5 National Space Weather Program 63 A.6 Summary and Findings 64 A.7 Notes and References 66 B STATEMENT OF TASK 68 C BIOGRAPHIES OF COMMITTEE MEMBERS 70 D ACRONYMS AND ABBREVIATIONS 74