Filling Gaps in the Spatial Coverage of LOLA Terrain Models

The Lunar Orbiter Laser Altimeter (LOLA) aboard the Lunar Reconnaissance Orbiter (LRO) has collected over 5.6 billion measurements of surface height with a vertical precision of ~10 cm and an accuracy of ~1 m. The ability of LOLA to obtain measurements under uniform illumination conditions and in shadowed regions provides an advantage over passive stereoscopic imaging, particularly at high latitudes (> 60 deg) where imaging is hindered by low solar incidence angles. This has allowed LOLA to produce the highest resolution and most accurate polar terrain models to date. However, due to LRO's polar orbit, gaps in the LOLA coverage as wide as ~4 km still exist near the equator. Here we present preliminary results of efforts to fill in gaps in LOLA coverage with targeted off-nadir spacecraft slews and by incorporating an independently-derived terrain model into the data post-processing. Recently, the Terrain Camera (TC) aboard the SELENE (Kaguya) spacecraft produced a global digital elevation model (DEM) from stereo imaging with 10-m spatial posting. The TC DEM is a highly complimentary dataset with which to augment the LOLA dataset. We show that the TC DEM can be registered to the LOLA geodetic framework yielding a root-mean-square elevation residual of a few meters. The goal of this work is to produce the most complete global terrain model of the lunar surface by merging both high-resolution datasets while preserving the accuracy of the LOLA data.