Prototype of Cryogenic Solar Absolute Radiometer and Transfer Radiometer for On-Board Calibration of Spectral Earth Imager

Abstract

We describe a prototype calibration system for the Traceable Radiometry Underpinning Terrestrial- and Helio-Studies (TRUTHS) satellite mission. We outline the design and testing of key system components, including the Cryogenic Solar Absolute Radiometer (CSAR). CSAR is designed to make Total Solar Irradiance (TSI) measurements with a standard uncertainty of < 0.01 % and provide SI-traceable calibration of a hyperspectral Earth imager (EI) over the wavelength range 320 nm – 2450 nm. The EI is designed to make Solar Spectral Irradiance (SSI) and spectral radiance measurements with a standard uncertainty of < 0.3 %.