Spring Season Approximation for Earth's Solar-band Radiance at the Moon, Revised

This data file is a revised version of the Mendeley file "Earthshine as an Illumination Source at the Moon", doi:10.17632/xfjm6nmh3m.1. It accompanies the manuscript "Earthshine as an Illumination Source at the Moon" by Glenar et al., submitted to Icarus on 2/27/2018, and revised 9/10/2018 . It presents a simple formulation for approximating Earth's spectral radiance at the Moon, as a function of:

1. Earth's phase angle
2. sub-observer position, i.e. Earth's longitude and latitude from the perspective of a lunar observer, and
3. wavelength

This approximation was computed by fitting to a grid of NASA Virtual Planetary Laboratory (VPL) models covering Mar-April 2008. Wavelength coverage is 0.30 to 2.5 microns. The approximation is valid for sub-observer latitudes between 30S and 30N (i.e. from a lunar perspective), and Earth orbital phase angles less than 60 degrees. Earth's diurnal average light curve is represented by a double Henyey-Greenstein phase function. Diurnal brightness modulation is represented by the change in observable land fraction over an Earth rotation. Diurnal effects not explained by land fraction are attributed to cloud variability. To within the uncertainties, this approximation is also valid for summer solstice, based on an examination of one additional VPL model series. Other seasons have not been examined.

The data file includes tabulated values of the coefficients and their uncertainties, and it describes the steps needed to compute radiance estimates as a function of wavelength.