A long baseline tracking network for improved NavIC orbit determination

Currently, the orbit determination accuracy of Navigation with Indian Constellation (NavIC) satellites is better than 20 m using the measurements from one-way ranging network of stations. The NavIC ephemerides along with time are continuously transmitted from the NavIC satellites. The transmitted ephemerides are also known as the broadcast ephemerides. These ephemerides are functions of precise orbit determination and dynamical model used for the orbit propagation and are one of the major error sources in the NavIC receiver position. In this paper, a study has been carried out to improve the orbit determination. This is performed through the precise orbit determination using extended tracking network with a sufficiently long baseline tracking stations (LBTS). We first attempted to fix a suitable number of LBTS based on several criteria, such as geometry, elevation cut-off angle, minimum tracking duration, etc. LBTS are optimally selected to reduce the along-track, in-track and cross-track errors in the estimated orbit. We also address the precise orbit determination of NavIC satellites by employing a weighed least square differential correction method. In the orbit determination process, the numerical integration orbit propagator using Cowell’s method, a step-by-step algorithm, is utilized. The simulated one-way range measurements are used for the precise orbit determination with a white noise sigma of 10 cm. We found that the observed position accuracy improvements are better than 10 m.