|A satellite is comprised of a payload supported by a platform.
The platform takes up the largest proportion of the mass of the satellite - design
objectives is therefore to support the largest possible payload with the smallest possible
- Physical support structure
- Thermal control
- AOCS (altitude control and stationkeeping)
- TTC&M (telemetry and telecommand)
- control processor
- Antenna sub-systems
- Communications transponders (receivers, amplifiers etc)
Major Spacecraft Sub-Systems:
Payload Block Diagram:
satellite in the GSO can "see" about one third of the Earth's surface so can provide
telephone, data and TV links over the whole of that area.
However, coverage is impossible to the polar regions (beyond about ±80º latitudes). (An
aircraft at 30,000 feet can still communicate at latitude 85º)
MSS satellite antennas commonly have maximum gain (about 21 dBi) at the edge of coverage,
and lower gain (18 dBi) at beam centre.
Three geostationary satellites at 120º spacing provide full Earth coverage (except for the