l20_satellitettc

l20_satellitettc - Satellite Telemetry, Tracking and...

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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 • Command System functions – Encoding/Decoding – Messages – Interfaces • Telemetry systems – Sensors and transducers – ADC –Fo rma t s – Concerns/Design principles October 29, 2003
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• 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 • 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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• 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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Subsystem Requirement Attitude Determination and Control Antenna pointing Command and Data Handling Command and telemetry data rates Clock, bit sync,and timing requirements Two-way comm requirements
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l20_satellitettc - Satellite Telemetry, Tracking and...

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