Satellite telemetry Tracking and Control Subsystems Col Johne keesee October 29. 2003 Massachusetts Institute of Technology
Satellite Telemetry, Tracking and Control Subsystems Col John E. Keesee October 29, 2003 Massachusetts Institute of Technology 1
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 spacecrafts functions and condition from the ground October 29. 2003 Massachusetts Institute of Technology
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
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
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
tt&c functions Carrier tracking Command reception and detection Telemetry modulation and transmission Ranging Subsystem operations October 29. 2003 Massachusetts Institute of Technology
TT&C Functions • Carrier tracking • Command reception and detection • Telemetry modulation and transmission • Ranging • Subsystem operations October 29, 2003 Massachusetts Institute of Technology 4
Carrier Tracking Two-way coherent communication Transmitter phase-locks to the received fre equency 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
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
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
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
Subsystem Operations 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 October 29. 2003 Massachusetts Institute of Technology
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
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
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
Tt&c interfaces Subsystem Requirement Attitude Determination and Antenna pointing Control Command and data Command and telemetry data rates Handling Clock, bit sync, and timing requirements Two-way comm requirements Autonomous fault detection and recovery Command and telemetry electrical interface Electrical Power Subsystem Distribution requirements Thermal/Structural Heat sinks for TWtas Heat dissipation of all active boxes Location of tT&c subsystem electronics Clear field of view and movement for all antennas Pa abroad Storing mission data RF and EMc interface requirements Special requirements for modulation and coding October 29. 2003 Massachusetts Institute of Technology
TT&C Interfaces 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 Autonomous fault detection and recovery Command and telemetry electrical interface Electrical Power Subsystem Distribution requirements Thermal/Structural Heat sinks for TWTAs Heat dis sipation of all active boxes Location of TT&C subsystem electronics Clear field of view and movement for all antennas Payload Storing mission data RF and EMC interface requirements Special requirements for modulation and coding October 29, 2003 Massachusetts Institute of Technology 9
Command system Reconfigures satellite or subsystems in response to radio signals from the ground Command timing Immediate Delayed Priority driven(ASAp) October 29. 2003 Massachusetts Institute of Technology
Command System • Reconfigures satellite or subsystems in response to radio signals from the ground • Command timing – Immediate – Delayed – Priority driven (ASAP) October 29, 2003 Massachusetts Institute of Technology 10
