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

This data file 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 is described in Section 5 of the manuscript by Glenar et al., "Earthshine as an Illumination Source at the Moon" (submitted to Icarus on 2/27/2018.) It was computed by fitting to a grid of NASA Virtual Planetary Laboratory (VPL) models covering Mar-April 2008. This approximation and uncertainties are therefore restricted to spring season, but it is expected the functional form is general enough to extend to other seasons by a simple adjustment of parameter values. A description of the approximation function is included in the data file, along with tabulated parameter values and and the steps needed to compute radiance estimates as a function of wavelength.