Design of a Mars data relay and navigation satellite network

Planetary exploration will be increasingly carried on by means of formations/fleets of probes, all of them having onboard navigation and communication systems. It is possible to keep these subsystems at a very simple level onboard of the probes, and to use some common external infrastructure to help them in exploiting these tasks. The common infrastructure could be represented by a network of satellites orbiting round the planet and providing a data relay to the Earth and a set of sources for a radionavigation system. The present paper, related to the Mars case, aims to focus on the architecture of such a network, the main driver being to build it with a minimum number of platforms, in order to save on launch and deployment, and to keep it as simple as possible, in order to increase reliability. The proposed design is to inject the network on a singled sunsynchronous, dusk-dawn orbital plane. Satellites take advantage of this special orbital geometry, and therefore can rely on simplified thermal design and almost constant power input. Their attitude is considered as nadir-pointing, and could be passively controlled by means of gravity gradient. Performances of such a design are compared with respect to other configurations previously presented in literature, showing its interest as a simplest solution.