Towards improved lunar reference frames: LRO orbit determination

Abstract

Lunar reference systems are currently realized by sets of coordinates of the few laser reflectors deployed by Apollo astronauts and unmanned Soviet spacecrafts. Expanding this coordinate knowledge to other features identifiable in images of the lunar surface requires highly accurate orbits of the acquiring spacecraft. To support such activities using images and altimetry data from the Lunar Reconnaissance Orbiter (LRO), an independent processing facility for tracking observations to LRO has been established. We present orbits from 1 year radio Doppler, radio ranging and laser ranging data obtained by different combinations of data types. To obtain an external confirmation for the achieved orbit accuracy, coordinates of the Apollo 15 reflector were measured in LRO images by photogrammetric techniques and compared to reference values from Lunar Laser Ranging (LLR). Coordinate differences were found to be at the 10m level.