Spacecraft Attitude Determination Using Terrestrial Illumination Matching

An algorithm to conduct spacecraft attitude determination via terrestrial illumination matching (TIM) is presented consisting of a novel method that uses terrestrial lights as a surrogate for star fields. Although star sensors represent a highly accurate means of attitude determination with considerable spaceflight heritage, TIM provides a potentially viable alternative in the event of star sensor malfunction or performance degradation. The research defines a catalog of terrestrial light “constellations,” which are then implemented within the TIM algorithm for position acquisition of a generic spacecraft bus. With the algorithm relying on terrestrial lights rather than the establish standard of star fields, a series of sensitivity studies are showcased to determine performance during specified operating constraints, to include varying orbital altitude and cloud cover conditions. Also, a comparison of relative accuracy will be presented for TIM with a generic star sensor.