There are significant complications to using the Moon as a radiometric standard source, primarily resulting from the variegation of the surface albedo, the constantly changing lunar phase and librations, and the strong dependence of the surface reflectance function on phase angle. However, the lunar surface reflectance properties are extremely stable, and therefore knowable to high precision. The practical considerations of using the Moon for instrument calibration call for the use of a model, which can predict the lunar brightness for the precise geometry of illumination and viewing of the instrument. Such a model, once established, is valid for any observation of the Moon within the geometry range, including those made in the past.
The USGS lunar calibration program has found the most useful application for satellite calibration involves treating the Moon's brightness as a disk-equivalent irradiance, derived from spatial integration of radiance pixels over the entire lunar disk.
A preliminary version of a spatially resolved radiance model has been developed by the USGS program. Such a model is of utility for e.g. instruments that cannot capture the entire Moon in their field of regard.
U.S. Department of the Interior | U.S. Geological Survey | U.S.G.S. Astrogeology
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