Radiometrically Accurate Hyperspectral Measurements for Benchmarking and Inter-Calibration

Earth climate studies require radiometrically accurate and spectrally resolved measurements of the Earth’s surface and atmosphere. Earth-scene measurements having high radiometric accuracy provide a benchmark of the current system. Inter-calibrations to other space-borne instruments spatially and temporally extend these high-accuracy measurements via those missions’ observations. Two upcoming spaceflight instruments will provide reference radiometric benchmark measurements and inter-calibrations to other space assets across the 350- to 2300-nm spectral range. The CLARREO Pathfinder’s HySICS instrument is an Earth-viewing hyperspectral imaging spectrometer to be operated from the International Space Station. It will inter-calibrate other instruments using simultaneous nadir overpasses. The 6U CubeSat ARCSTONE will calibrate the spectral lunar irradiance, enabling the intrinsically stable Moon to be an on-orbit reference viewable by other spacecraft instruments, giving an inter-calibration source that spans all time. Both use a novel on-orbit solar-irradiance cross-calibration approach to achieve high radiometric accuracies, as the Sun is the best-known spectral reference available on orbit.