Reference Inter-Calibration Ability of CLARREO Reflected Solar Imaging Spectrometer

The CLARREO Reflected Solar (RS) imaging spectrometer is designed to provide on-orbit calibration standard with SI-traceable accuracy of 0.3% (2 sigma) over the mission lifetime. The the goal of reference inter-calibration is to enable rigorous decadal change observations of critical climate change components including reflected broadband radiation (CERES), decadal change in cloud properties (VIIRS/MODIS/AVHRR), and surface albedo changes including snow and ice albedo feedback.

The CLARREO RS approach for reference inter-calibration is based on the highly accurate spectral reflectance and reflected radiance measurement to establish on orbit reference for existing Earth viewing reflected solar radiation sensors: CERES and VIIRS on NPP and NPOESS satellites, as well as AVHRR and follow-on imagers on METOP. The mission goal is to be able to provide sufficient numbers of space/time/angle matched samples of these instruments with the CLARREO/RSIS reference observations to overcome the random error sources from imperfect data matching and instrument noise.

The inter-calibration method is to monitor over time changes in targeted sensor response function parameters: effective offset, gain, non-linearity, spectral response function, and sensitivity to polarization of optics. In this study we used existing satellite data (SCIAMACHY, CERES, PARASOL) and simulation methods to determine requirements for CLARREO RS inter-calibration sampling and data matching.