Comparison of image restoration methods for lunar epithermal neutron emission mapping

Orbital measurements of neu tro ns by the Lunar Explori ng Neutron Detector (LEN D) onboard the Lunar Reconnaissance Orbiter are being used to quantify the spatial dis tribution of near surface hydrogen (H). In fe rred H concentration maps have low signal-to-noise (SN) and image restoration (IR) techniques are being studied to enhance results. A single-blind. two-phase study is described in which four teams of researchers independently developed image restora tion techn iques optimized for LEND data. Synthetic lunar epithermal neutron emission maps were derived from LEND simulations. These data were used as ground truth to determine the relative quantitative perfo rmance of the IR methods vs. a defau lt denoi sing (s moothing) technique. We review and used fa ctors influencing orbital remote sensing of neutrons emitted from the lunar surface to develop a database of synthetic "true" maps for performance evaluation. A prior independent tra ining phase was implemented for each technique to assure methods were optimized before the blind trial. Method performance was determined using several regional root-mean-square error metries specific to epithermal signals of interest. Res ults ind icate unbiased IR methods realize on ly small signal gains in most of the tested metrics. This suggests other physically based modeling ass umptions are required to produce appreciable signal gains in similar low SN IR applications.