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Article 12 Mars Reconnaissance Orbiter Telecommunications DESCANSO Design and Performance Summary Series Article 12 Mars Reconnaissance Orbiter Telecommunications Jim Taylor Dennis K. Lee Shervin Shambayati Jet Propulsion Laboratory California Institute of Technology Pasadena, California National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California September 2006 This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Prologue Mars Reconnaissance Orbiter The cover image is an artist’s rendition of the Mars Reconnaissance Orbiter (MRO) as its orbit carries it over the Martian pole. The large, articulated, circularly shaped high-gain antenna above the two articulated paddle-shaped solar panels points at the Earth as the solar panels point toward the Sun. This antenna is the most noticeable feature of the communications system, providing a link for receiving commands from the Deep Space Stations on the Earth and for sending science and engineering information to the stations. The antenna is larger than on any previous deep-space mission, and the amplifiers that send the data on two frequencies are also more powerful than previously used in deep space. Included in the command data and the science data is information that the orbiter relays to and from vehicles on the surface as it passes over them. The orbiter uses the Electra transceiver and a smaller low-gain antenna for this communication. The antenna is the smaller. gold-colored cylinder pointed toward the surface. The transceiver is the first Electra flown, and it has the capability to communicate efficiently with surface vehicles such as Phoenix and Mars Science Laboratory. By necessity, this article is a prologue, as it was completed just after the orbiter successfully went into orbit around Mars and began reducing orbit altitude and circularizing the orbit in preparation for the science mission. The orbit changing was accomplished through a process called aerobraking, in preparation for the beginning of two years of science starting in November 2006, followed by two years with the emphasis on relaying data with surface vehicles starting in November 2008. To indicate the communications data volume anticipated, the image below is a mosaic of the ground covered in the first image of Mars taken by the High Resolution Imaging Science Experiment (HiRISE) camera. The full product was 20,000 pixels wide by 9,500 pixels high for a total of about 50 gigabits (Gb) of data. It took about 11 hours for MRO to downlink the data to the Deep Space Network at an effective rate of about 1.3 megabits per second (Mbps). iii DESCANSO DESIGN AND PERFORMANCE SUMMARY SERIES Issued by the Deep Space Communications and Navigation Systems Center of Excellence Jet Propulsion Laboratory California Institute of Technology Joseph H. Yuen, Editor-in-Chief Previously Published Articles in This Series Article 1—“Mars Global Surveyor Telecommunications” Jim Taylor, Kar-Ming Cheung, and Chao-Jen Wong Article 2—“Deep Space 1 Telecommunications” Jim Taylor, Michela Muñoz Fernández, Ana I. Bolea Alamañac, and Kar-Ming Cheung Article 3—“Cassini Orbiter/Huygens Probe Telecommunications” Jim Taylor, Laura Sakamoto, and Chao-Jen Wong Article 4—“Voyager Telecommunications” Roger Ludwig and Jim Taylor Article 5—“Galileo Telecommunications” Jim Taylor, Kar-Ming Cheung, and Dongae Seo Article 6—“Odyssey Telecommunications” Andre Makovsky, Andrea Barbieri, and Ramona Tung Article 7—“Deep Space 1 Navigation: Extended Missions” Brian Kennedy, Shyam Bhaskaran, J. Edmund Riedel, and Mike Wang Article 8—“Deep Space 1 Navigation: Primary Mission” Brian Kennedy, J. Edmund Riedel, Shyam Bhaskaran, Shailen Desai, Don Han, Tim McElrath, George Null, Mark Ryne, Steve Synnott, Mike Wang, and Robert Werner Article 9—“Deep Impact Flyby and Impactor Telecommunications” Jim Taylor and David Hansen Article 10—“Mars Exploration Rover Telecommunications” Jim Taylor, Andre Makovsky, Andrea Barbieri, Ramona Tung, Polly Estabrook, and A. Gail Thomas Article 11—“Mars Exploration Rover Navigation” Louis A. D’Amario iv Table of Contents Foreword....................................................................................................................................ix Preface........................................................................................................................................x Acknowledgements....................................................................................................................xi Section 1 Mission Phases and Orbit Summary........................................................................1 1.1 Mission Objectives......................................................................................1 1.2 The MRO Spacecraft...................................................................................1 1.3 Mission Phases............................................................................................3 1.3.1 Launch..........................................................................................3 1.3.2 Cruise ...........................................................................................3 1.3.3 Approach and Mars Orbit Insertion...............................................4 1.3.4 Aerobraking..................................................................................4 1.3.5 Primary Science Mission...............................................................5 1.3.6 Relay Mission ...............................................................................6 1.3.7 Safe Mode.....................................................................................7 1.4 The MRO Orbit and Its Relay Coverage for Surface Vehicles .....................8 1.5 MRO Orbit Phasing to Support Landing Vehicle EDL ..............................11 Section 2 Telecommunications Subsystem Overview ...........................................................12 2.1 X-Band: Cruise and Orbital Operations .....................................................12 2.1.1 High-Gain Antenna.....................................................................15 2.1.2 Low-Gain Antenna......................................................................17 2.1.3 Transponders ..............................................................................18 2.1.4 RF Amplifiers.............................................................................19 2.2 UHF: Proximity Relay Communications ...................................................21 2.2.1 Proximity-1 Data ........................................................................28 2.2.2 Time Stamp Packets....................................................................28 2.2.3 Raw Data....................................................................................28 2.2.4 Phase and Power Data.................................................................28 2.2.5 Open-Loop Data .........................................................................28 2.3 Ka-Band: Operational Demonstration........................................................28 Section 3 Ground Data System.............................................................................................30 3.1 Deep Space Network.................................................................................30 3.2 Ka-Band Demonstration Requirements......................................................30 3.3 Ground Data Network Flow for Relay Through Electra.............................31 Section 4 X-Band Telecom Operations.................................................................................34 4.1 Cruise Calibrations....................................................................................34 4.2 MOI Telecom Configurations....................................................................34 4.3 Aerobraking Telecom Configurations........................................................35 v 4.4 Downlink Telemetry Modulation and Coding............................................35 4.4.1 Short Frame Concatenated (Table 4-2)........................................36 4.4.2 Long Frame Concatenated (Table 4-3) ........................................36 4.4.3 Turbo Code (Tables 4-4 Through 4-6).........................................37 4.4.4 RS-Only (Table 4-7) ...................................................................38 4.5 X-Band Link Performance Summaries ......................................................39 4.6 Coordinating MRO and MER X-Band Operations.....................................42 Section 5 Ka-Band Operational Demonstration ....................................................................45 5.1 Ka-Band Operational Demonstration Overview.........................................45 5.2 Ka-Band Link Prediction and Performance During Cruise.........................45 5.3 Spacecraft Constraints and Operational Factors.........................................47 5.4 Cruise Delta-DOR Operations and Performance........................................49 5.5 Nominal Ka-Band Link Operation During the Science Mission .................50 5.6 Solar Conjunction Experiments.................................................................51 Section 6 UHF Calibrations and Operations .........................................................................52 6.1 UHF System Tests During Cruise..............................................................52 6.2 Phoenix Support........................................................................................52
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