Simulated Positioning Performance of the JPL Mars Network Operating in Conjunction with the European Netlanders Mission

Kyle O'Keefe, Gérard Lachapelle, and Susan Skone

Abstract:	The purpose of the research described in this paper is to determine through simulation if the proposed six satellite Mars Network constellation and proposed four lander Netlanders network can be used together (satellites plus ground control) to establish a Global Navigation Satellite System for Mars that can operate independently of Earth based observations and control. This paper presents positioning performance results of several simulations of the Mars Network constellation both with and without the Netlanders component. First, the positioning geometry of the Mars Network is assessed planet-wide using availability, pass statistics and dilution of precision as figures of merit. This is done by simulating the orbits of the Mars network satellites using a Keplerian plus first order drift of the ascending node representation of the orbit. Results show that instantaneous point positioning will only be available at low latitudes and then only sporadically. However, static ground users will be able to determine their positions by observing multiple satellite passes, though some locations on the planet will have to wait up to several hours before obtaining a reliable position fix. Simulated observations are then generated by precisely modeling the trajectories of the satellites using numerical integration of the equations of motion taking into account higher order gravity, solar radiation pressure, and tidal effects. These trajectories, along with the positions of the Netlanders landers are used to calculate inter-satellite and satellite-ground ranges and range rates. Simple models for atmospheric errors are presented and used to create more realistic observations. These observations are then used to simulate a lander positioning itself by making observations of passing satellites while relying on sub-optimal orbit information. The four landers are found to be able to position themselves to within 10 m after between one and four hours of tracking. The position estimates of each lander converge over the course of several hours, but then diverge slightly as the orbital errors grow. The ability of the satellites to improve their orbit solutions by tracking the ground stations is an area of continuing research. However, preliminary results indicate that three of the proposed Netlanders would make poor ground control stations as they are located at latitudes with poor satellite coverage.
Published in:	Proceedings of the 2004 National Technical Meeting of The Institute of Navigation January 26 - 28, 2004 The Catamaran Resort Hotel San Diego, CA
Pages:	614 - 623
Cite this article:	O'Keefe, Kyle, Lachapelle, Gérard, Skone, Susan, "Simulated Positioning Performance of the JPL Mars Network Operating in Conjunction with the European Netlanders Mission," Proceedings of the 2004 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2004, pp. 614-623.
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