Antenna Scanning B ehniques for Estimation of Spacecraft Position

Scanning movements are added to a tracking antenna's trajectory to estimate the true spacecraft position. T h e scanning movements are composed of the harmonic axial movements of an antenna. This motion produces power variations of t he received signal, which are used to estimate the spacecraft's position. Three different scanning patterns (conical scan, Lissajous scan, and rosette s can ) are presented and analyzed in this paper. The analysis includes the evaluation of the estimation errors d u e to random or harmonic variation of the antenna's position, and d u e to random and harmonic variations of t he power level. Typically, the estimation of the spacecraft's position is carried out afler completing a full scanning cycle. Sliding-window scanning is introduced in this paper, wherein the spacecraft-position estimation is carried out in an almostcontinuous manner, and it reduces the estimation time by half.