Estimation of the Accuracy of Geostationary Satellite Observations

Continuous monitoring of artificial space objects requires periodic quality control of observational data. Estimating the internal accuracy of observations in the form of an RMS error of positions makes it possible to monitor and detect outliers in primary data array. For artificial satellites of the Earth, the orbital elements calculated at the Research Institute Nikolaev Astronomical Observatory (RI NAO) can be externally compared with the data of the International Laser Ranging Service (ILRS) or the Global Navigation Satellite System (GNSS). Such a comparison makes it possible to detect time synchronization problems and to identify and evaluate systematic errors. At the RI NAO, regular observations of artificial satellites in different orbits using several telescopes have been carried out for more than 10 years, and a catalog of orbital elements in the two-line element (TLE) format is maintained. The software for calculating orbital elements has been developed in cooperation with the Astronomical Observatory of the Odessa National University. This article presents the analysis of the processing results of an array of observations from 149 geostationary satellites (GSS’s). The observations have been made during 2020…2021 using the RI NAO telescope complex. Time synchronization has been provided by the Resolution-T GPS receiver with an RMS error of 40 ns. All GSS observations have been carried out using the combined observation method developed at the RI NAO. A total of 134 461 GSS positions have been obtained for which the residual O–C differences with respect to the orbit calculated at the RI NAO have been determined. The RMS error of the GSS positions in the apparent magnitude range 9^m…13^m is 0.5″ in right ascension and declination. A comparison of the GSS orbital positions calculated from the RI NAO orbital elements and the ILRS website data shows that the differences between the corresponding geocentric Cartesian coordinates at the start of the prediction are dX = 0.72 km, dY = –0.52 km, and dZ = 1.28 km.