Signal-In-Space User Range Error Assessment via Combined Space and Ground-based Measurement Data

James A. DiLellio

Abstract:	This paper presents a simulation of SIS URE based on Kalman filter estimates of satellite ephemeris and clock states using simulated pseudorange measurements. Unlike the current operational GPS control segment, the model presented in this paper generates and processes both space- based and ground-based measurements. The ground-based measurements are simulated from the existing five GPS monitoring stations (MSs). The inter-satellite measurements are generated based on a Ka-band crosslink architecture with low noise characteristics. Assuming a suitable communication system is enabled to distribute the measurements to a central processing location, ground and spaced based measurements are edited and fed into a Kalman filter to generate state estimates of satellite position velocity and clock, as well as MS clock, over each filter update period. The simulation presented in this paper consists of several key components, including a spacecraft propagator module, a measurement generation module, a state prediction/correction module, and a performance calculation module. The modular design is intended to allow for alternative model implementations to be available as an option prior to run time. For example, the simulated truth and predictive models for tropospheric delay can be selected from one of three models. The paper concludes with simulated filter performance to help quantify the impact of combined ground and space- based measurements on the Kalman filter estimation process. Crosslink range data is simulated at up to 3 spacecraft in view, both in and out of plane, of a given satellite. The simulation demonstrates that the addition of crosslink measurements reduces estimation error and improves filter stability. The majority of the estimation error improvements are observed in the in-track and cross- track directions local to the satellite.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	1500 - 1510
Cite this article:	DiLellio, James A., "Signal-In-Space User Range Error Assessment via Combined Space and Ground-based Measurement Data," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 1500-1510.
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