A Lunar Spectral Flux Database for Quantitative Viirs Day/night Band Environmental Applications

Visible-band (e.g., 0.4-0.7 μm) satellite radiometers are used almost exclusively for daytime observations, when a significant amount of sunlight reflection is available. Silicon photodetectors offer adequate sensitivity to a broad range of daytime visible light (e.g.,10 to 10 W/m-sr-μm). Examples of such sensors include the visible channels on the Advanced Very High Resolution Radiometer (AVHRR), the MODerate Resolution Imaging Spectroradiometer (MODIS), and the Geostationary Operational Environmental Satellite (GOES) imager. Visible light is also prevalent during the nighttime hours, albeit at significantly lower levels or confined to relatively small. Nighttime lights typically require a very high degree of amplification to be detectable from the satellite platform. Examples of nighttime lights include both artificial (e.g., city lights, gas flares, fishing boat lights) and natural (moonlight, lightning, aurora, and bioluminescence) sources (e.g., Croft [1978]). Of particular interest to nighttime environmental applications is the use of moonlight in the same way as the sun—enabling equivalent daytime applications which require measurements of visible reflectance. The requirement for doing so is an accurate specification of the downwelling top-of-atmosphere (TOA) lunar spectral irradiance (flux). Unlike the downwelling TOA solar flux, the lunar flux varies dramatically across the lunar cycle (new moon to full moon) and with sun/earth/moon (S/E/M) geometry. This paper summarizes the development of a high resolution (1 nm) lunar spectral spectral flux model designed to enable quantitative applications from the calibrated Day/Night Band (DNB) to fly on board the National Polar-orbiting Operational Environmental Satellite System’s (NPOESS) Visible/Infrared Imager/Radiometer Suite (VIIRS).