Measuring moonlight: An overview of the spatial properties, lunar coverage, selenolocation, and related Level 1B products of the Moon Mineralogy Mapper

The Moon Mineralogy Mapper (M-3), a high-resolution, high-precision imaging spectrometer, flew on board India's Chandrayaan-1 Mission from October 2008 through August 2009. This paper describes some of the spatial sampling aspects of the instrument, the planned mission, and the mission as flown. We also outline the content and context of the resulting Level 1B spatial products that form part of the M-3 archive. While designed and planned to operate for 2 years in a 100 km lunar orbit, M-3 was able to meet its lunar coverage requirements despite the shortened mission; an increase of the orbit altitude to 200 km; and several relevant problems with spacecraft attitude, timing, and ephemeris. The unexpected spacecraft issues required us to invent a novel two-step approach for selenolocation. Leveraging newly available Lunar Reconnaissance Orbiter-Lunar Orbiter Laser Altimeter (LOLA) topography and an improved spacecraft ephemeris, we have created a method that permits us to bootstrap spacecraft attitude estimates from the image data themselves. This process performs a nonlinear optimization to honor a set of data-derived image-to-image tie points and image-to-LOLA control points. Error analysis of the final results suggests we have converged to a selenolocation result that has image-to-image root-mean-square (RMS) errors less than 200 m and image-to-LOLA RMS errors less than 450 m, despite using data-derived spacecraft attitude results. The Level 1B products include the lunar coordinates resulting from this inversion process and 10 relevant observational geometry parameters that fully characterize the ray tracing geometry on a pixel-by-pixel basis.