Sun-Synchronous Orbits

The Physics of Space Security a reference manual David Wright, Laura Grego, and Lisbeth Gronlund © 2005 by David Wright, Laura Grego, and Lisbeth Gronlund All rights reserved. ISBN#: 0-87724-047-7 The views expressed in this volume are those held by each contributor and are not necessarily those of the Officers and Fellows of the American Academy of Arts and Sciences. Please direct inquiries to: American Academy of Arts and Sciences 136 Irving Street Cambridge, MA 02138-1996 Telephone: (617) 576-5000 Fax: (617) 576-5050 Email: [email protected] Visit our website at www.amacad.org Contents xi PREFACE 1 SECTION 1 Introduction 5 SECTION 2 Policy-Relevant Implications 13 SECTION 3 Technical Implications and General Conclusions 19 SECTION 4 The Basics of Satellite Orbits 29 SECTION 5 Types of Orbits, or Why Satellites Are Where They Are 49 SECTION 6 Maneuvering in Space 69 SECTION 7 Implications of Maneuvering for Satellite Mass 77 SECTION 8 Getting Things into Space: Rockets and Launch Requirements 89 SECTION 9 Space-Basing 109 SECTION 10 Elements of a Satellite System 117 SECTION 11 Overview of Interfering with Satellite Systems 151 SECTION 12 Topics in Interfering with Satellites 177 CONTRIBUTORS Contents in Detail Preface xi Section 1 INTRODUCTION 1 Section 2 POLICY-RELEVANT IMPLICATIONS 5 Section 3 TECHNICAL IMPLICATIONS AND GENERAL CONCLUSIONS 13 Section 4 THE BASICS OF SATELLITE ORBITS 19 Motion in Space vs. Motion in the Atmosphere 19 Orbital Basics 19 Orbital Speed of Satellites 20 Orbital Period of Satellites 22 Orientation of the Plane of the Orbit 23 Elliptical Orbits 24 APPENDIX: CIRCULAR AND ELLIPTICAL ORBITS 26 Circular Orbits 26 Elliptical Orbits 27 Section 5 TYPES OF ORBITS, OR WHY SATELLITES ARE WHERE THEY ARE 29 The Constraints of Geometry 29 The Motion of Satellites Relative to the Surface of the Earth 29 Elevation Angle of the Satellite 32 Observable Ground Area 34 Transmission Time 36 Effects of the Local Environment 36 Interference 36 Radiation Environment 37 Effects of the Atmosphere 39 More Complicated Effects of Gravity 40 Common Orbits 40 Low Earth Orbits 40 Circular Medium Earth Orbits 42 Molniya Orbits 42 Tundra Orbits 43 Geostationary Orbits 43 Sun-Synchronous Orbits 44 Lagrange Points 45 APPENDIX: DETAILS OF ELEVATION ANGLE AND GROUND AREA 47 Elevation Angle 47 Ground Area Viewed by a Satellite 47 Section 6 MANEUVERING IN SPACE 49 Basic Satellite Maneuvers 49 Maneuvers within the Orbital Plane 50 Changing the Shape of the Orbit 50 Changing the Altitude of a Satellite in a Circular Orbit 51 Changing the Orbital Period 53 Changing the Relative Location of Satellites in the Same Orbit 53 Maneuvers that Change the Orbital Plane 54 Maneuvers to Change Inclination 54 Rotating the Orbital Plane at Constant Inclination 56 De-orbiting Maneuvers 57 Reentry Heating 59 Stationkeeping 60 APPENDIX: TECHNICAL DETAILS OF MANEUVERING 62 Changing the Shape of the Orbit 62 Maneuvering Between Circular Orbits 63 Changing the Period of a Satellite 64 Changing the Inclination of the Orbit 64 Rotating the Orbital Plane at Constant Inclination 64 General Rotations 65 De-orbiting 65 Stationkeeping 66 Section 7 IMPLICATIONS OF MANEUVERING FOR SATELLITE MASS 69 Satellite Mass 69 The Potential Impact of New Technologies 71 Conventional Thrusters 72 Electric Arcjet Thrusters 72 Ion Thrusters 73 Nuclear Propulsion 74 APPENDIX: THE ROCKET EQUATION 75 Derivation of the Rocket Equation 75 The Time Required for a Maneuver 76 Section 8 Getting Things into Space: Rockets and Launch Requirements 77 Using Missiles to Launch Payloads to High Altitudes: the “1/2 Rule” 77 Putting Objects into Orbit 77 Factors that Affect Launch Capability 80 Placing Satellites in Geostationary Orbit 81 Air Launching 82 Launch Costs 83 Appendix A: Potential and Kinetic Energy of Satellites85 Appendix B: The “1/2 Rule” 86 Section 9 SPACE-BASING 89 Space-Based Kinetic Ground-Attack Weapons 89 Constellation Size 90 Comparison to Delivery by Ballistic Missile 94 Space-Based Boost-Phase Missile Defense 96 Vulnerabilities of SBI 97 Constellation Size and Launch Requirements 98 ASAT Capability of SBI 101 The Military Space Plane 101 APPENDIX: COMPARISON OF THE MILITARY SPACE PLANE VERSUS MULTIPLE LAUNCHES 105 Deploying Multiple Satellites 105 Inspector Satellites 107 Section 10 ELEMENTS OF A SATELLITE SYSTEM 109 Satellite Components 109 Ground Stations 114 Links 114 Section 11 OVERVIEW OF INTERFERING WITH SATELLITE SYSTEMS 117 Electronic Interference: Jamming and Spoofing 118 Jamming or Spoofing the Downlink 119 Jamming or Spoofing the Uplink 121 Laser Attacks on Satellite Sensors 123 Dazzling 125 Partial Blinding 128 High-Powered Microwave Attacks 130 Destruction 133 Attacks on Ground Stations 133 Laser Attacks on Satellites: Heating and Structural Damage 134 Kinetic Energy Attacks 135 Electromagnetic Pulse from a High-Altitude Nuclear Explosion 138 APPENDIX A: LASER POWER REQUIRED FOR DAZZLING 140 APPENDIX B: ANGULAR SIZE, RESOLUTION, AND BEAM DIVERGENCE 143 Angular Size and Resolution 143 Beam Divergence 144 APPENDIX C: FRAUNHOFER DIFFRACTION PATTERN 145 APPENDIX D: POWER ESTIMATE FOR LASER BLINDING 147 Section 12 TOPICS IN INTERFERING WITH SATELLITES 151 Space-Based ASATs and Space Mines 151 Covert Space-Based ASATs 152 Space-Based ASATs vs. Ground-Based ASATs 154 Simple Ground-Based Pellet (Non-Homing) ASAT 157 Uncertainty in Satellite Position 160 Inaccuracy in Positioning the Pellet Cloud 161 Timing Errors 162 Results of the Calculation 162 Conclusions 164 The Global Positioning System and Reconnaissance Satellites 165 The Global Positioning System 165 Reconnaissance Satellites 169 APPENDIX: CALCULATING THE EFFECTIVENESS OF A PELLET ASAT 172 Contributors 177 Preface Over the past decade or so, societies around the world have relied increasingly on satellites for vital communication services, environmental monitoring, navigation, weather prediction, and scientific research. This largely beneficial trend is expected to intensify: more countries are developing satellite technol- ogy and using the services derived from it. The same technologies have made possible the development of military capabilities in space that go far beyond those employed during the Cold War for intelligence gathering early warning. Some in the United States see space as a critical enabler for bringing decisive military force to bear anywhere on Earth with little or no warning. This rapid strike capability is a central element of the post-9/11 national security strategy, which seeks not only to deter or defeat any potential aggressor but also to prevent the acquisition of threatening capabilities by hostile states or terrorist groups. Protecting and enhancing U.S. military capability in space is emerging as an important focus of military planning. Recent official documents have proposed, for example, various anti-satellite and space-based weapons to protect and augment U.S. capabilities in space. These new missions are controversial in the view of close U.S. allies and are likely to be contested by others if pursued. Serious public discussion of military space plans has not yet occurred in the United States, though important questions of policy, planning and budgeting loom: What missions are best carried out from space? What are the likely costs and available alternatives to various space weapons proposals? How susceptible are satellites to interference? How easily can they be disabled or destroyed? What measures can be taken to reduce their vulnerability? The answers to these questions depend on physical laws and technical facts that are not widely understood outside of a rather narrow slice of the science and engineering community. The paper that follows makes accessible to a general audience the necessary facts upon which an informed evaluation of space policy choices can take place. The authors, physicists David Wright, Laura Grego, and Lisbeth Gronlund, describe the mechanics of satellite orbits and explain why certain operations are suited to particular orbits. They dis- cuss the requirements for launching satellites into space and maneuvering them once in space. They consider the consequences of the space environment for basing certain military missions there. Finally, they describe the elements of a satellite system and assess the vulnerability of these components to various types of interference or destruction. They also include an analysis of technical measures for reducing satellite vulnerability. The paper makes no attempt to provide policy recommendations. Although the authors’ views on space weapons and missile defense are well known to those who follow these issues, they are not asserted here. Instead, PREFACE xi the intent is to provide a neutral reference. Those engaged in the policy process, no matter what their views, should find this work useful. This paper is part of the American Academy’s “Reconsidering the Rules of Space” project. The study examines the implications of U.S. policy in space from a variety of perspectives, and considers the international rules and principles needed for protecting a long-term balance of commercial, military, and scientific activities in space. The project is producing a series of papers, intended to help inform public discussion of legitimate uses of space, and induce a further examination of U.S. official plans and policies in space. Forthcoming papers will consider the interaction of military, scientific, and commercial activities in space; Chinese and Russian perspectives on U.S. space plans; and the possible elements of a more comprehensive space security system. The authors presented parts of the paper at a workshop convened by the American Academy and its Committee on International Security Studies in December 2003. Participating were Bruce Blair, Steve Fetter, Nancy Gallagher, Richard Garwin, Subrata Ghoshroy, Joan Johnson-Freese, Carl Kaysen, George Lewis, Martin Malin, Jonathan McDowell, Norman Neureiter, Pavel Podvig, Theodore Postol, John Rhinelander, John Steinbruner, Eugene Skolnikoff, Larry S. Walker, and Hui Zhang. We thank the participants for their insights at the workshop. We also thank Richard Garwin, George Lewis, and two anonymous reviewers for their comments on the paper.

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