LINKED, AUTONOMOUS, INTERPLANETARY SATELLITE ORBIT NAVIGATION (LiAISON) IN LUNAR HALO ORBITS

In this study, simulated Satellite-to-Satellite Tracking (SST) measurements for space-craft in lunar halo orbits were used to investigate the feasibility of Liaison Navigation. The lunar halo orbits were generated using the circular restricted three-body problem. Through covariance analysis, it was found that the position and velocity vectors for all participating spacecraft were observable using Liaison Navigation methods (using only crosslink range without Earth-based tracking). The accuracy of the Liaison Naviga-tion orbit estimates was compared for various constellation geometries. The accuracy was better for orbits that did not remain near the lunar orbit plane and for orbits with shorter periods. The orbit accuracy decreased as the separation distance between the spacecraft decreased, meaning that close formations could not effectively use Liaison Navigation. A range bias was successfully included as an estimated parameter and its effect on the orbit accuracy was shown. The effect on the orbit accuracy was also shown for simulations that included constant force model errors. It was found that Liaison Navigation performed very well for certain constellation geometries. Monte Carlo analysis was used to investigate the validity of the covariance. It was found that the covariance was slightly optimistic, probably due to correlation between the two satellite state estimates. With the type of current on-board hardware available, it should be possible to achieve 1 orbit errors on the order of 10 m using Liaison Navigation in lunar halo orbits