Antenna scanning techniques for estimation of spacecraft position

Scanning movements are added to tracking antenna trajectory to estimate the true spacecraft position. The scanning movements are composed of harmonic axial movements of an antenna. This scanning motion produces power variations of the received signal, which are used to estimate spacecraft position. Three different scanning patterns (conical scan, Lissajou´s scan, and rosette scan) are presented and analyzed in this paper. The analysis includes the evaluation of the estimation errors due to random or harmonic variation of the antenna position and due to random and harmonic variations of the power level. Typically, the estimation of the spacecraft position is carried out after completing a full scanning cycle. In this paper sliding window scanning is introduced, wherein the spacecraft position estimation is carried out in an almost continuous manner, and it reduces estimation time by half.