THE USE OF THE CONICAL SCAN EARTH SENSOR IN COMMUNICATION SATELLITE APPLICATIONS

Abstract

Infra-red horizon sensors are almost universally used as the primary attitude sensor for pitch and roll on present day three-axis stabilized communication satellites. When used with a momentum wheel, yaw is also controlled without direct sensing. The application flexibility of the mechanically scanned Conical Earth Sensor, and it’s recent availability as a component designed for precision, long life performance have resulted in renewed interest in its use on communication satellites. The Conical Earth Sensor will provide accurate on-orbit attitude sensing in pitch and roll. It can provide attitude sensing all the way from the shuttle orbit to synchronous for booster control, and is particularly attractive for multiple burn, multiple orbit transfer. It can provide accurate nadir sensing 100% of the time in the highly elliptical Molniya twelvehour orbit. It can facilitate wide angle attitude sensing for antennae calibration maneuvers. It can be used in a static mode as a horizon crossing indicator for spacecraft that go up as spinners, and then for normal on-orbit sensing as a scanner. It can be readily hardened to both nuclear and lazer threats, unlike static sensors that are highly susceptible to thermal transients. It has a simple, rugged, and stable construction that is not sensitive to resonance effects from other mechanical devices on the spacecraft such as momentum or reaction wheels.