Jack T. Wilson, et al., report that they present improved resolution maps of the Lunar Prospector Neutron Spectrometer thermal, epithermal and fast neutron data and Gamma-Ray Spectrometer Th-line fluxes via global application of pixon image reconstruction techniques. With the use of mock data sets, we show that the pixon image reconstruction method compares favorably with other methods that have been used in planetary neutron and gamma-ray spectroscopy.
The improved thermal neutron maps are able to clearly distinguish variations in composition across the lunar surface, including within the lunar basins of Hertzsprung and Schrodinger. The improvement in resolution reveals a correlation between albedo and thermal neutron flux within the craters. The consequent increase in dynamic range confirms that Hertzsprung basin contains one of the most anorthositic parts of the lunar crust, including nearly pure anorthite over a region tens of km in diameter. At Orientale, the improvement in spatial resolution of the epithermal neutron data show that there is a mismatch between measures of regolith maturity that sample the surface and those that probe the near-subsurface, which suggests a complex layering scenario.
They concluded that in using mock data sets, several image reconstruction and deconvolution techniques commonly used with planetary gamma-ray and neutron data were possible. Using mock datasets, we found that the pixon methods are most effective at improving the resolution of, and suppressing noise in, these data at all SNRs and for all PSF footprint sizes. However, the resolution improvement achieved was found to be dependent on both the SNR and the structure of the image being reconstructed.
Reconstruction of low-SNR, images with few distinct features yields only a reduction in noise.
We applied the pixon image reconstruction methods to the LP NS and GRS Th-line data. The improved resolution, achieved via image reconstruction, allows for direct identification of features in the NS/GRS datasets and higher-resolution spectroscopic and imaging data. We saw that the high Clementine 750 nm / 415 nm reflectance ratio feature in Copernicus matches the low-Th region, revealing a FHT-like composition in the centre of the Procellarum KREEP Terrane. Similarly, improving the resolution allows the identification of high albedo regions within Hertzsprung and Schrodinger basins with high thermal neutron flux.
[Why didn't authors include uranium in their investigations .... curious. See (more) in Chapter 9.].
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