Title: Hyperspectral Imagery Radiometry Improvements for Visible and Near-Infrared Climate Studies
Primary Author: Kopp, Greg
Organization: LASP
Co-Author(s): Ginger Drake, Joey Espejo, David Harber, Karl Heuerman, Peter Pilewskie, Yolanda Roberts, and Paul Smith
Laboratory for Atmospheric and Space Physics, Univ. of Colorado

Abstract:
We describe two studies to determine requirements and improve accuracies for the CLARREO mission's benchmark measurements of Earth climate in the visible and near-infrared spectral regions.

A science study helps clarify the requirements of the CLARREO Earth-viewing measurements in these spectral regions, which sample the solar-reflected radiance from the ground and atmosphere. This study 1) helps define the CLARREO benchmark measurement requirements in the visible and near-infrared, and 2) examines potential benefits from cross-calibrating other on-orbit Earth-viewing instruments to improve their accuracies or extend the CLARREO observations spatially or temporally. These results help determine instrument measurement requirements for absolute accuracy, long-term stability, spectral resolution, global coverage, and spatial resolution.

An Instrument Incubator Program study will demonstrate a new method to improve radiometric accuracy for hyperspectral imaging in the visible and near-infrared by on-orbit cross-calibrations using spectral solar irradiance. Unlike traditional solar diffuser-based calibrations, the methods to be demonstrated utilize direct observations of the Sun. Maintaining low uncertainty in the ratio of incoming to outgoing Earth radiances establishes a benchmark climate measurement and transfers solar irradiance calibrations to Earth-viewing spatial/spectral instrumentation. A visible and near-infrared prototype hyperspectral imager will demonstrate and quantify the accuracies to which this calibration transfer can achieve end-to-end on-orbit radiometric calibrations and long-term stability corrections.

We describe these NASA-funded studies intended to refine CLARREO measurement requirements based on the mission's science requirements and improve the on-orbit radiometric accuracy of spectral measurements for the mission in the visible and near-infrared.