Precise Modeling of Solar Radiation Pressure for IRNSS Satellite

Abstract

IRNSS-1A, IRNSS-1B and IRNSS-1C are the first three satellites of Indian Regional Navigation Satellite System (IRNSS) launched in 1^st July 2013,4^th April 2014 and 16^th October 2014 respectively. IRNSS will provide regional navigation services independently over the IRNSS service area. For the precise positioning and navigation applications, precise orbit and clock information of the IRNSS satellites are essential. For High altitude satellites like IRNSS, Solar Radiation Pressure (SRP) force is the second largest perturbation force acting on the satellites after the gravitational attraction from Earth, Sun and Moon. It is the largest error source in the modelling of orbital dynamics of IRNSS, and hence its precise modelling is essential for accurate orbit determination. In this paper different approaches were studied to develop a highly precise solar radiation pressure model for IRNSS satellites using IRNSS-1A and IRNSS-1B observation data. Since IRNSS satellites shape, optical properties, physical properties as well as the attitude information are different from other Indian Communication satellites, a novel approach has been adopted here for precise modelling of SRP. The force due to SRP has been computed analytically for each of the spacecraft surfaces in the satellite body fixed frame which is further resolved in all required directions to compute the net force. To evaluate the performance of the SRP model, the orbit accuracy is derived from 1-day orbit overlaps at day boundaries of 2-day solutions. As a result, an orbit estimation accuracy of 25 meters has been observed by the model alone, while the estimation error is observed as 2.5m.Further beside the model, 3 constant co-efficient has been estimated in the three particular directions (namely DYB) which were following a right handed system. Again the model performance with estimated co-efficient has been analysed and the orbit accuracy is derived from the overlap test. As a result, an orbit estimation accuracy of 10 m has been observed, while the estimation error is about 1m.

Keywords: IRNSS, Navigation, Solar Radiation Pressure, orbit accuracy