The communication engineers need to evaluate footprint movement to deploy a ground station. Geostationary communication satellite's inclination angle causes the movement of a satellite footprint. The calculation of the inclination angle requires complex astronomical knowledge and mathematical calculations. On the other hand, a satellite communication engineer does not need a very accurate inclination angle value to design a ground station for required service availability. We propose a practical method called trigonometric curve fitting for the inclination to solve the problem. The past and the future value of inclination can be evaluated by using the curve-fitting method. It is a simplified practical method and does not need advanced orbital dynamics knowledge. The orbit geometry and evaluated inclination angle are used for estimation of a coverage area movement. A satellite communication engineer can evaluate coverage area oscillation quickly and design a better link for an inclined orbit satellite by using the proposed method. We have evaluated the inclination angle of the communication satellite Sat-1 with the proposed method. Sat-1 spot beam movements and wide beam coverage area movements are estimated to obtain EIRP and G/T fluctuation for link budget purposes. The proposed method provides the results that are consistent with the results of measurements and the results of satellite operators' professional tools.
A Regional positioning system using three geosynchronous Turksat satellites is investigated in this paper. In this system, a time code signal sent from an earth station to three geostationary satellites is received by a user on Earth. Time delay differences from three satellites are measured by the user and are used to calculate the user's position. The user's location information includes latitude and longitude coordinates. It is assumed that the user's altitude is measured by an altimeter.
No abstract
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 [2]. Multiple numbers of colocated 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 Turksat Satellite Control Center.
Satellite operators utilize a two-stations turn around ranging (TAR) system to reduce the ground station measurement system's complexity and cost while having the same or better orbit determination accuracy for communication satellites orbit determination recently. This study investigates two stations' performance, four-way ranging on communication satellite orbit determination, operational conformance, and cost. The observation data sets are collected using traditional single station tracking (SST) and the new method TAR. The computed results using the Monte Carlo method encourage the satellite operators to use a four-way ranging system to observe and measure required data sets. TAR performance is evaluated, taking SST as a reference. The six classical orbital elements (a, e, i, RAAN, AoP, and TA) are compared for large numbers of observation data. The SST and TAR results are very close to each other. The worst-case calculated Euclidian distance between SST and TAR is 1.893 km at the epoch below the 6 km success criteria. The TAR observation method is appropriate to collect data sets for precise orbit determination. This work result indicates that satellite operators should consider deploying TAR stations to collect two-station range data sets and compute the orbit for nominal north-south station-keeping maneuvers (NSSK) and east-west station-keeping (EWSK) maneuver operations. The TAR method is superior to SST in terms of accuracy, operational conformance, and costs.
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