CLARREO Pathfinder Inter-calibration: Requirements and Objecti

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a Tier 1 mission recommended by the NRC Decadal Survey 2007. In 2016, NASA allocated funding for a CLARREO Pathfinder mission to demonstrate essential measurement technologies required for the full mission. The allocated funds support the flight of a Reflected Solar spectrometer, hosted on the International Space Station (ISS) in the 2023 time-frame. One of the major objectives of CLARREO Pathfinder mission is to demonstrate on-orbit sensor inter-calibration. The CLARREO Pathfinder approach for reference inter-calibration is based on measuring spectral reflectance with high accuracy and establishing an on-orbit reference for operating Earth viewing sensors: CERES and VIIRS. The mission goal is to be able to provide CLARREO reference observations that are matched in temporal, spectral, and angular domains with measurements from the aforementioned instruments, with sampling sufficient to overcome the random error sources from imperfect data matching. The inter-calibration method is to monitor changes in targeted sensor response function parameters: effective offset, gain, non-linearity, spectral response function, and sensitivity to polarization. We will present the CLARREO Pathfinder project status, development of its inter-calibration approach and algorithms, and expected sampling estimates