Spacecraft Position Estimation and Attitude Determination using Terrestrial Illumination Matching

An algorithm to conduct spacecraft position estimation and 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, with Global Positioning System (GPS) providing position, TIM provides a potentially viable alternative in the event of star sensor or GPS 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 established 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. The pose is recovered from the matching techniques by solving the epipolar constraint equation using the Essential and Fundamental matrix, and point-to-point projection using the Homography matrix. This is used to obtain relative position change and the spacecraft\u27s attitude when there is a measurement. When there is not, both an extended and an unscented Kalman filter are applied to test continuous operation between measurements. The research is operationally promising for use with each nighttime pass, but filtering is not enough to sustain orbit determination during daytime operations