Positioning of Geostationary Satellite by Radio Interferometry

There are several perturbations that force the satellite orbit to deviate from the elliptical form. To cope with these perturbations, station keeping is applied. For accurate station keeping, determination of the true satellite orbit is necessary. Radio interferometry is one of the techniques used for determining azimuth and elevation look angles of a satellite. In this paper, we introduce three structures based on interferometry for determining the view angles of satellites. The estimated angles are combined with range measurement for orbital positioning of geostationary (GEO) satellites. In the proposed interferometry structures, to acquire the required angular accuracy, the distance between antennas is set larger than the maximum half-wavelength, and the incurred ambiguities are resolved by utilizing properties of GEO satellites. For each of the proposed structures, maximum likelihood estimators are proposed. It is shown that, in low measurement noise cases, these proposed estimators are unbiased and their mean square error achieves the Cramer-Rao bound.