Optical Ranging Measurement with a Lunar Orbiter: Limitations and Potential

摘要

Ranging measurements provide precision distance between spacecraft on planetary mission and ground stations. Navigators, radio scientists, and planetary scientists use ranging for their applications and have collectively advanced the precision. Currently, conventional ranging is carried out coherently with radio links. Optical ranging promises several order of magnitude improvements over radio ranging. This study analyzes one-way uplink optical ranging data collected by the Lunar Reconnaissance Orbiter on a solar system scale. Analysis was approached from a navigation perspective to determine the quality of the optical ranging data. Because of the nature of one-way data, which use two different clocks to construct a range, special attention was paid to properly modeling the spacecraft clock, and several approaches are presented to model the clock. Trajectories computed using optical ranging data both match the published trajectory within the published uncertainty and result in a residual root mean square of 9-26 cm, several orders of magnitude improvement in root mean square from radio ranging (10 m S-band on the Lunar Reconnaissance Orbiter). Biases introduced by the spacecraft clock dominate the measurement; adding a more stable clock (such as the Deep Space Atomic Clock) or using a coherent system would improve the data type by decreasing these errors.