| Four measurement options for Orion autonomous optical lunar navigation are analyzed using linear covariance analysis methods. The measurements include a feature tracking camera measurement, star landmark elevation measurement, star horizon elevation measurement, and star occultation measurement. Based on trade studies performed, the star landmark measurement is superior to the star horizon measurement closer to the lunar surface, while the horizon sensor has better performance above an altitude of several thousand kilometers. The feature tracking camera performs comparably to the star landmark measurement. The star occultation camera is the worst performer throughout all trajectories due to the inability to include measurements continuously. However, its ability to take occultation measurements on the sunlit or eclipsed side of the Moon makes it a valuable aid to the crater-based measurements, which can only be taken over a sunlit surface. |
