High-accuracy Mars approach navigation with radio metric and optical data

The aerocapture of a space vehicle on hyperbolic approach to Mars results in tight navigation requirements at atmospheric entry. The purpose of this paper is to examine several different methods for approach navigation and to determine what accuracies are possible. The methods are broken into four groups as follows (1) navigation with only Deep Space Network (DSN) tracking of the approach vehicle, (2) navigation with the DSN plus ranging between the approach vehicle and spacecraft in orbit about Mars, (3) navigation with the DSN plus optical data involving the Martian moons, and (4) navigation with DSN range data and differenced range data involving the approach spacecraft and orbiters at Mars. If the current modeling errors that affect earth-based radio metric data, such as errors in tracking station locations, the Martian ephemeris, and differences in the quasar and planetary coordinate frames, are improved, then perhaps earth-based tracking could meet the entry error requirements imposed by aerocapture. If not, then the other three options of intervehicular range, optical data, or differenced range provide highly accurate entry knowledge at least twelve hours before entry.