Optical monitoring of inter satellite distance between Turksat-2A And Turksat-3A

Geostationary satellites are objects, which revolve around the Earth where orbits are nearly circular and located on the equator plane with a period exactly equal to the rotation of the Earth. Most of such satellites are used for civil and military communication, television broadcasting and weather forecasting. Gravitational forces of the Sun, Moon and non-uniform mass distribution of the Earth perturb the geostationary orbits. Including these gravitational anomalies pressure of Solar winds is another source of perturbation. Because of these perturbations, orbits of geostationary satellites disturbed and some correction maneuvers must be performed. ITU radio regulation requires geostationary satellites have capability of maintaining their positions within ±0.1° of the longitude of their nominal positions. Multiple numbers of co located geostationary satellites can be operated within ±0.1° box with careful orbit determination and maneuver strategies. Most orbit determinations of the geostationary satellites are performed by tone ranging; measuring phase difference of RF signals sent to satellite and received from the satellite. Angular parameters of the satellites are obtained by azimuth and elevation of the control station antennas, which are following beacon signal of the satellite. Because of all geostationary satellites must be located on geostationary orbit, collision risk always exists. Telescope observation of geostationary satellites provides us to complimentary information to tone ranging systems, which can be used for correlation and calibration purposes. In this study, inter-satellite distances of co-located Turksat-2A and Turksat-3A satellites measured by telescope observations. This optical observation performed in 2011 at the Ankara University Observatory (AUO) using 20 cm (8-inch) optical telescope and with a CCD type detector. The inter-satellite distances are calculated by using the observed angular measurements between Turksat-2A and Turksat-3A and the radial distance measured with tone ranging. Results are compared with tone ranging orbit measurements performed by Turks at Satellite Control Center.