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.

本数据集是曼德利（Mendeley）平台上题为《地球反照作为月球的照明源（Earthshine as an Illumination Source at the Moon）》的文件的修订版本，其数字对象标识符（DOI）为10.17632/xfjm6nmh3m.1。本数据集配套Glenar等人撰写的同名手稿，该手稿于2018年2月27日提交至《伊卡洛斯（Icarus）》期刊，并于2018年9月10日完成修订。
本数据集提供了一种用于近似月球视角下地球光谱辐亮度的简易计算公式，其输入变量包括：1. 地球相位角；2. 月球观测者视角下的地球次观测点位置（即地球的经纬度）；3. 波长。该近似公式通过拟合2008年3月至4月期间的美国国家航空航天局（National Aeronautics and Space Administration, NASA）虚拟行星实验室（Virtual Planetary Laboratory, VPL）模型网格计算得到，波长覆盖范围为0.30至2.5微米。
该近似公式的适用条件为：月球视角下次观测点纬度介于南纬30°至北纬30°之间，且地球轨道相位角小于60°。地球的日平均光变曲线采用双亨耶-格林斯坦（Henyey-Greenstein）相位函数进行表征；日亮度调制通过地球自转周期内可观测陆地占比的变化描述，无法通过陆地占比解释的日变化效应则归因于云量变化。基于对另一组VPL模型序列的验证，在误差范围内该近似公式同样适用于夏至场景，其余季节的适用性尚未得到考察。
本数据集包含系数及其不确定度的制表值，并说明了基于波长计算辐亮度估算值所需的步骤。