Reference Inter-Calibration Ability of the CLARREO Reflected Solar Spectrometer and JPSS Sensors

The CLARREO Reflected Solar Imaging Spectrometer (RSIS) is designed to provide an on-orbit calibration standard with SI-traceable accuracy of 0.3% (k=2) over the mission lifetime. CLARREO reference inter-calibration measurements are intended to provide rigorous observations over decadal time scales of critical climate change components including reflected broadband radiation (CERES), decadal change in cloud properties (VIIRS), and surface albedo changes including snow and ice albedo feedback.

The CLARREO RSIS approach for reference inter-calibration is based on obtaining highly accurate spectral reflectance and reflected radiance measurements to establish an on-orbit reference for existing Earth viewing reflected solar radiation sensors: CERES and VIIRS on JPSS satellites, as well as AVHRR and follow-on imagers on METOP. The mission goal is to be able to provide CLARREO/RSIS reference observations that are matched in space, time, and viewing angles with measurements from the aforementioned instruments, in amounts sufficient 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 RSIS inter-calibration sampling and data matching.