The ARCSTONE Project to Calibrate Lunar Reflectance

The purpose of the ARCSTONE project is to more accurately measure the spectral lunar reflectance so the Moon can be used as a high-accuracy SI-traceable exo-atmospheric calibration standard for Earth-viewing instruments in low-Earth orbits. The spectral range is 350 nm to 2300 nm with less than 4 nm sampling. Radiometric modeling indicates the mission goal of better than 1 % (k=1) absolute accuracy is achievable. To reach this goal, the instrument will measure solar and lunar irradiances with a single set of optics, thereby minimizing the impact of long-term optical degradation via a temporally-close ratio method. SI-traceable results will be obtained by scaling the solar irradiance measurements to the calibrated, on-orbit Total and Spectral Irradiance Sensor (TSIS) observations. To date, a first-generation ARCSTONE prototype has been developed and is undergoing system-level characterizations. A more compact second-generation engineering design unit that will fit in a 6U CubeSat is under development.