SATELLITE NETWORK PROVIDING CONTINUOUS COMMUNICATIONS TO SUPPORT MANNED AND UNMANNED EXPLORATION OF THE INNER- PLANETS A Master Thesis Submitted to the Faculty of American Public University by Ralph Leroy Spangler, Jr. In Partial Fulfillment of the Requirements for the Degree of Master of Science July 26, 2016 American Public University Charles Town, WV The author hereby grants the American Public University System the right to display these contents for educational purposes. The author assumes total responsibility for meeting the requirements set by United States copyright law for the inclusion of any materials that are not the author’s creation or in the public domain. © Copyright 2016 by Ralph Leroy Spangler, Jr. All rights reserved. 2 DEDICATION I dedicate this thesis to my wife and sons. Without their encouragement, patience, understanding, support, and most of all, love, the completion of this work would not have been possible. I cannot leave out my faithful furry companion, Veritas, who patiently laid at my feet while I worked. 3 ACKNOWLEDGMENTS I wish to thank the instructors, administration, and fellow students of American Military University for their support, insight, differing viewpoints, openness, and sometimes humor. Their commitment and involvement in my time of studies has been most appreciated. From the beginning, they reinforced the confidence I have in my abilities not only to complete a Master’s degree, but to complete it with excellence. I have found my course work throughout the Space Studies program to be stimulating and thoughtful, providing me with the tools and knowledge with which to explore past, present and future ideas and issues. 4 ABSTRACT OF THE THESIS SATELLITE NETWORK PROVIDING CONTINUOUS COMMUNICATIONS TO SUPPORT MANNED AND UNMANNED EXPLORATION OF THE INNER- PLANETS by Ralph Leroy Spangler, Jr. American Public University System, July 26, 2016 Charles Town, West Virginia Professor Dimitry Bizyaev, Thesis Professor This thesis provides an evaluation of a possible inner-planetary communications network that would provide continuous coverage of manned and unmanned missions. It examines the network’s ability to provide continuous coverage during times of occultation, or being obscured by an astronomical body from Earth’s reference point. The examination is conducted using computer simulation and mathematical modeling. The results show that a network of satellites that include Earth ground stations, relay satellites at Earth-Sun Lagrange points L4 and L5, and a minimal constellation around the planet or moon can provide continuous coverage. Due to the extreme distances involved, a real-time communications network will not be possible, regardless, the benefit of a continuous communications satellite network will provide a solution to signal loss during times of occulting, reduce signal acquisition times, allow for smaller receiving antennas, redundancy, and survivability. 5 Table Of Contents Table Of Contents ............................................................................................................. 6 Table of Figures ................................................................................................................. 8 Table of Tables ................................................................................................................ 10 1 INTRODUCTION .................................................................................................. 11 1.1 Research Goal .............................................................................................................. 11 1.2 Research Motivation ................................................................................................... 12 1.3 Summary ...................................................................................................................... 13 2 LITERATURE REVIEW ...................................................................................... 15 2.1 Introduction ................................................................................................................. 15 2.2 Moon and Beyond ....................................................................................................... 17 2.2.1 Moon Constellation ..................................................................................................... 18 2.3 Mars ............................................................................................................................. 19 2.3.1 Mars Constellation ...................................................................................................... 20 2.4 Lagrange Points .......................................................................................................... 22 2.5 Inner-Planetary Network Connectivity, Performance, Reliability ........................ 23 2.6 Summary ...................................................................................................................... 24 3 APPROACH TO ANALYSIS ................................................................................ 25 3.1 Introduction ................................................................................................................. 25 3.2 Modeling Occulting of Mars ...................................................................................... 26 3.3 Mars Constellation Modeling ..................................................................................... 31 3.4 Earth-Mars Network Modeling ................................................................................. 32 6 3.4.1 Network Performance, Survivability ........................................................................ 35 3.5 Summary ...................................................................................................................... 39 4 DATA ANALYSIS .................................................................................................. 40 4.1 Introduction ................................................................................................................. 40 4.2 Occulting of Mars ....................................................................................................... 40 4.3 Mars Constellations .................................................................................................. 46 4.4 Network Performance, Survivability ........................................................................ 47 4.5 Summary ...................................................................................................................... 51 5 DISCUSSION and CONCLUSION ...................................................................... 53 5.1 Introduction ................................................................................................................. 53 5.2 Restatement of Research Goal ................................................................................... 53 5.3 Research Motivation ................................................................................................... 53 5.4 Conclusions .................................................................................................................. 54 5.5 Significant Results of Research .................................................................................. 55 5.6 Recommendations for Future Research ................................................................... 55 APPENDIX A .................................................................................................................. 57 A.1 GMAT Occulting Model Configuration Parameters .................................................... 57 References ........................................................................................................................ 62 7 Table of Figures FIGURE 1: DIAGRAM ILLUSTRATING THE CONFIGURATION OF THE EARTH-SUN LAGRANGE POINTS. S IS THE SUN, E IS THE EARTH, L1 – L5 ARE THE LAGRANGE POINTS. L4 AND L5 ARE STABLE, EQUILIBRIUM POINTS IN SPACE REQUIRING MINIMAL STATION KEEPING DUE AND ALLOW SIGNALS TO BE ROUTED AROUND THE SUN. ......................................................................................... 23 FIGURE 2: AREA ZONE OF SIGNAL LOSS CAUSED BY OCCULTATION OF MARS BY THE SUN (NOT TO SCALE). PERIODIC SIGNAL LOSS WILL OCCUR AS THE SUN COMES BETWEEN THE EARTH AND MARS. THIS IS A TEMPORARY CONCERN AS THE PLANETS CONTINUE IN THEIR ORBITS. ...................................................... 27 FIGURE 3: THE SHADOW CAST OR ZONE OF SIGNAL LOSS INCREASES AS THE DISTANCE TO SUN DECREASES. WHEN MARS IS AT ITS PERIHELION THE DISTANCE THAT EARTH WILL TRAVEL THROUGH WILL INCREASE. ................ 28 FIGURE 4: THE POSITION OF RELAY SATELLITES AT EARTH-SUN LAGRANGE POINTS L4 AND L5 PROVIDES FOR ROUTING OF THE COMMUNICATIONS AROUND THE SUN AND UNOBSTRUCTED PATH TO MARS. (NOT TO SCALE) .. 29 FIGURE 5: IN DETERMINING THE LENGTH OF SHADOW, ZONE OF SIGNAL LOSS, EARTH TRAVELS THROUGH, SEVERAL PARAMETERS NEED TO BE USED AS INDICATED IN THE DIAGRAM. RELATIVISTIC EFFECTS OF THE STRONG GRAVITATIONAL EFFECT OF THE SUN ARE NOT CONSIDERED. ......................... 30 FIGURE 6: DIAGRAM SHOWING THE COMMUNICATIONS PATH USING THE RELAY SATELLITES AT EARTH-SUN L4 AND L5. COMMUNICATIONS WILL BE ROUTED THROUGH EITHER OR BOTH OF THE RELAY SATELLITES WHEN THE SUN OCCULTS MARS. THERE WILL BE AN INCREASE IN LATENCY DUE TO THE ADDED DISTANCE TO THE PATH. (NOT TO SCALE) ................................................ 33 FIGURE 7: THE EARTH-MARS COMMUNICATIONS NETWORK IS DEPICTED