Antenna scanning techniques for estimation of spacecraft position

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