Geometric analysis of visibility of mission support infrastructure for phobos and deimos

A high-precision navigation system to support robotic and human missions to Mars in the next 20 to 30 years could be greatly enhanced by the development of an architecture that uses the Martian moons. Placing navigational beacons on the moons, whose positions can be determined from Earth with high accuracy, would provide the necessary reference points for a more extensive Mars Positioning System (including stations on the moons and in orbit about Mars), our could be used as a communications relay between Earth and Mars. In addition to permitting high-precision position determination for surface and space elements in ongoing Mars missions, the system would aid mission designers and planetary geologists in refining knowledge of the Martian gravitational field. To make use of such a system, a beacon must be visible to various locations. First, it must have visibility to the surface of Mars. Second, it must have visibility to the sun to power its solar panels. Lastly, it must have visibility to the Earth, in order to provide a line-of-sight communications link from Mars to Earth. This paper presents a geometric assessment of the visibility characteristics of such as system through the entire synodic period of Earth and Mars for beacons placed on the moon surface facing Mars and the surface facing the leading edge of the moon in its orbit about Mars. It also compares these results with visibility assessments computed via the Satellite Tool Kit software. The analysis showed that placing a navigation beacon on the leading edge of Deimos provided the maximum visibility to both the Earth and the sun. However, if a communications relay between the surfaces of Mars and Earth were the prime consideration, a better geometry would be to place the beacon on the side of the moon facing Mars.