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

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.