Correcting flawed orbits with significant along-track offset in LOLA data to remove apparent noise in DEM

Abstract

The lunar orbiter laser altimeter (LOLA) onboard the lunar reconnaissance orbiter has performed high-precision, full-coverage, and high-density laser ranging observations for the entire lunar surface since its launch. Statistics have shown that LOLA has collected 6.94 billion effective altimeter data up to June 2022. Most of the typical orbits in the LOLA dataset have a high quality and exhibit horizontal offsets of almost 7 m and radial offsets of almost 0.5 m. However, there is still a category of orbits in the dataset that will cause apparent noise in the constructed DEM, which is attributed to the orbits with large or anomalous errors. We call such orbits as flawed orbits in this paper. The flawed orbits can be identified and screened by the elevation discrepancy at the crossovers of the orbits. The results show that the flawed orbits are caused by significant along-track errors, which also result in the radial error of up to several kilometers. Moreover, most of the flawed orbits are concentrated in several consecutive time intervals. A correction method is then proposed to correct the flawed orbits in the local region. The position of the flawed orbits is reconstructed using the feature points matching of the DEMs before and after they are removed. Some experimental analyzes show that the apparent terrain artifacts have been eliminated and more identifiable terrain details are reappeared. Identifying and correcting these flawed orbits with significant along-track offsets paves the way for improving the quality of the LOLA data and reconstructing the topography of the Moon.