Next-Generation Mars Network Position, Navigation, and Timing for Future Robotic and Human Explorers

A next-generation Mars Network is investigated to determine a configuration optimized for both communications and positioning performance for surface users. A previously proposed 6000 km altitude, 3-satellite equatorial constellation that was found to be optimal for communications to surface users located in the latitude range from 60°S to 60°N is shown to be deficient for surface positioning. Inclining the 3-satellite configuration between 30° and 50° improves positioning performance to users in this latitude range; however, due to a lack of coverage this improvement is primarily seen for positioning when using tracking data collected over long timespans. Moving to an inclined 6-satellite case and using a Walker 6/2/0 delta configuration, at selected inclinations and altitudes, greatly improves the positioning solution performance over shorter timescales, with the best performance obtained with orbits inclined at 50°. Also examined were continuous coverage global constellations that were compared to the Walker 50°: 6/2/0 configurations. The single fold continuous coverage Walker 55.7°:7/7/5 constellation slightly improves the positioning performance and provides more uniform and continuous coverage to the poles, which the Walker 50°:6/2/0 case cannot. Finally, a Walker 57.1°: 8/8/2 constellation that provides continuous twofold coverage was examined; however, the high altitude required for this case reduces its communication performance and yields poorer positioning performance relative to the Walker 55.7°:7/7/5. It is concluded that a next generation Mars Network with focused support to users between 60°S and 60°N that the Walker 50°: 6/2/0 is the best positioning and communications performance while, for continuous coverage global coverage, the Walker 55.7°: 7/7/5 is superior.