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Figure 2.8: Telemetry, Tracking, Command, and Monitoring
Figure 2.8 shows the typical TTC&M functional elements for the satellite
and ground facility for a communications satellite application.
The telemetry function involves the collection of data from sensors
on-board the spacecraft and the relay of this information to the
ground. The telemetered data includes such parameters as: voltage and
current conditions in the power subsystem, temperature of critical
subsystems, status of switches and relays in the communications and
antenna subsystems, fuel tank pressures, and attitude control sensor
status. A typical communications satellite telemetry link could involve
over 100 channels of sensor information, usually in digital form, but oc-
casionally in analog form for diagnostic evaluations.
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Satellite System Elements
