AOC
Satellite Communications Glossary
Satellite Communications — AOC
Information on AOC
The path of the satellite through space is called its
orbit; the orientation of the satellite in space is called
its attitude. Control of the orbital path is required to
ensure that the satellite is in the correct location in
space to provide the services required of it. Attitude control
is essential on the spacecraft to prevent the satellite from
tumbling in space and to ensure that the antennas remain
pointed at a fixed point on the Earth’s surface. These
functions are the responsibility of the Attitude and Orbit Control
Subsystem.
Orbit control is required to correct for perturbation forces,
and to transfer orbits, or orbital location. The major means
of changing orbits or to move or maintain current location
are to fire the thrusters.
A basic attitude control system comprises
three elements: an ability to sense the current attitude of
the platform, an ability to compute errors between current attitude
and desired attitude, and some mechanism by which the attitude
error can be controlled and corrected.
Spacecraft attitude can be determined
by one or more of the following sensors: Earth sensors,
Sun sensors, star trackers, radio frequency sensors, or gyroscopes. Once
errors in attitude are detected, control is then exercised through
one of a number of stabilisation methods. There are two
main stabilisation methods: two-axis, or spin stabilisation; and three-axis stabilisation.
Other techniques exist, the most useful of which is gravity-gradient
stabilisation.
Other topics in our resources on Satellite Communications related to AOC include:
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