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The Landsat Data Continuity Mission (LDCM) project at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) is supervising the manufacture and calibration of the Operational Land Imager (OLI) satellite instrument by Ball Aerospace in Boulder, Colorado. As part of that oversight function, the project is preparing a set of radiometers to monitor long-term changes (if any) in the radiance from the integrating sphere used for the radiance calibration of the OLI instrument. That sphere, calibrated at the National Institute of Standards and Technology (NIST), serves as an artifact for establishing traceability of the OLI radiance calibration to SI units, that is, to the radiance scale at NIST. This paper addresses the characterization of two Analytic Spectral Devices (ASD) Fieldspec spectrometers that are part of the NASA/NIST program to validate radiometric reference standards in the LDCM project. In particular, we report on a series of measurements at NIST to determine the ASD spectrometers' long-term stability. Along with other radiometers, the ASDs will be used in the monitoring of changes in the OLI reference sphere from its calibration at NIST to its use in the calibration of the OLI satellite instrument. The ASD stability measurements will continue through the conclusion of the calibration of OLI. |
