SINGLE-POINT POSITION ESTIMATION IN INTERPLANETARY TRAJECTORIES USING STAR TRACKERS

This study provides a closed-form single-point position estimation technique for interplanetary missions using visible planets observed by star trackers. The leastsquares solution is obtained by minimizing the sum of the expected object-space squared distance errors. A weighted least-squares solution is provided by an iterative procedure. The weights are evaluated using the distances to the planets estimated by the least-squares solution. It is shown that the weighted approach only requires one iteration to converge and results in significant accuracy gains. The light time correction is taken into account while the stellar abberation cannot be implemented in single-point estimation as it requires knowledge of the velocity. The proposed method is numerically tested in several statistical tests and for one-year interplanetary trajectory example with fixed attitude. The apparent planet magnitudes, the angle between observed visible planets (constrained by the sensor FOV), and the Sun-exclusion angle are computed throughout the trajectory. This study proves that, using a single star tracker pointing to visible planets, it is possible to provide reliable and accurate single-point position estimation in interplanetary missions.

SINGLE-POINT POSITION ESTIMATION IN INTERPLANETARY TRAJECTORIES USING STAR TRACKERS Conference Paper