Calibration Acquisitions of the Moon by CLARREO Pathfinder

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a Tier 1 mission recommended by the 2007 NRC Earth Science Decadal Survey. The mission\u27s technical objectives are to acquire high-accuracy SI-traceable decadal length Earth observations for climate records and to enable reference inter-calibration of other Earth observing sensors. The CLARREO Pathfinder (CPF) project has the key objective to demonstrate essential shortwave measurement technologies required for the full CLARREO mission. In January 2017, the CPF mission began formulation Phase-A. CPF will operate a Reflected Solar (RS) spectrometer to be launched in the 2021 timeframe to the International Space Station (ISS). The RS instrument will have contiguous spectral coverage from 350 nm to 2300 nm, with the science objective for absolute uncertainty \u3c0.3% (k=1). In addition to its primary purpose of acquiring Earth ground scenes, the CPF will observe the Moon when viewing opportunities are available from its mounting location on the ISS ExPRESS Logistics Carrier (ELC-1), Site 3. These observations will acquire above-atmosphere spatial/spectral measurements of the lunar disk at varying phase angles to be used for verifying sensor response stability, and also along-slit scans to be used for instrument flat-fielding. Given the accuracy goals of the RS instrument, the CPF radiometric measurements of the Moon may be used to improve the lunar spectral irradiance calibration standard, which in turn can help calibrate other on-orbit sensors. We will report on the lunar acquisitions and applications planned for the CLARREO Pathfinder mission