ORBIT COMPUTATION SYSTEM FOR “IRS”

Abstract This paper discusses the Orbit Computation System and precise orbit determination accuracies of the first operational Indian Remote sensing Satellite(IRS). The analysis presented describes navigational strategy, achievable accuracies in orbit determination and ground location in the processed imagery. A brief description of the scene framing procedure, orbit and scene information computation needed for Ancilary Computer Compatible Tape (ACCT), which would be subsequently used for processing various levels of imageries, is presented. The impetus for such analysis was originated with the need to meet mission objectives, precise orbit keeping and precision annotation in imagery which have put high accuracy requirements on orbit determination and processing. This necessitated improvement of tracking data systems, data handling techniques, improved dynamical models and computational techniques which include trajectory propagation. A brief description of orbit determination process is presented along with the tracking network configured for IRS during acquisition and normal phases. It is demonstrated under operational environment of IRS, that the position can be determined to an accuracy better than 500 meters. The analysis include orbit determination processing in the presence of live satellite data, viz. SPOT and LANDSAT as well as simulated data of IRS.