Spacecraft orbit propagator integration with GNSS in a simulated scenario

Abstract

When space vehicles operate above the Global Navigation Satellite System (GNSS) constellation or even above geosynchronous orbit, it is common that the traditional GNSS single–epoch solution can’t meet the requirement of orbit determination (OD). To provide the required OD accuracy continuously, a new designed spacecraft orbit propagator (OP) is combined with the GNSS observations in a deep integration mode. Taking both the computational complexity and positioning accuracy into consideration, the orbit propagator is optimized based on a simplified fourth order Runge-Kutta integral aided with empirical acceleration model. A simulation scenario containing a typical Highly-inclined Elliptical Orbit (HEO) user and GPS constellation is established on a HwaCreat™ GNSS signal simulator to testify the performance of the design. The numerical test results show that the maximum propagation error of the optimized orbit propagator does not exceed 1000m within a day, which is superior to conventional OPs. If the new OP is deeply integrated with GNSS in our proposed scheme, the 95% SEP for the OD accuracy is 10.0005m, and the time to first fix (TTFF) values under cold and warm start conditions are reduced by at least 7s and 2s respectively, which proves its advantage over loose integration and tight integration.