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l20_satellitettc

l20_satellitettc - Satellite Telemetry Tracking and Control...

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Satellite Telemetry, Tracking and Control Subsystems Col John E. Keesee October 29, 2003 Massachusetts Institute of Technology 1
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Overview The telemetry, tracking and control subsystem provides vital communication to and from the spacecraft TT&C is the only way to observe and to control the spacecraft’s functions and condition from the ground October 29, 2003 Massachusetts Institute of Technology 2
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Outline TT&C functions and trades Command System functions – Encoding/Decoding – Messages – Interfaces Telemetry systems Sensors and transducers – ADC – Formats Concerns/Design principles October 29, 2003 Massachusetts Institute of Technology 3
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TT&C Functions Carrier tracking Command reception and detection Telemetry modulation and transmission • Ranging Subsystem operations October 29, 2003 Massachusetts Institute of Technology 4
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Carrier Tracking Two-way coherent communication – Transmitter phase-locks to the received frequency – Transmitted frequency is a specific ratio of the uplink frequency Easy to find and measure the frequency received on the ground Doppler shift provides range rate October 29, 2003 Massachusetts Institute of Technology 5
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Ranging Uplink pseudo-random code is detected and retransmitted on the downlink Turnaround time provides range Ground antenna azimuth and elevation determines satellite angular location October 29, 2003 Massachusetts Institute of Technology 6
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Subsystem Operations October 29, 2003 Massachusetts Institute of Technology 7 Receive commands from Command and Data Handling subsystem Provide health and status data to CD&H Perform antenna pointing Perform mission sequence operations per stored software sequence Autonomously select omni-antenna when spacecraft attitude is lost Autonomously detect faults and recover communications using stored software sequence
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TT&C Trades Antenna size vs transmitter power Solid state amplifiers vs traveling wave tube amplifiers Spacecraft complexity vs ground complexity October 29, 2003 Massachusetts Institute of Technology 8
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TT&C Interfaces Subsystem Requirement Attitude Determination and Control Antenna pointing Command and Data Handling Command and telemetry data rates
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