Intercomparison Activities Support Global Land Observations
PL scientists recently completed the first in a series of intercomparison activities supporting the NASA’s Landsat Data Continuity Mission (LDCM). This project extends the legacy of the Landsat program, which has been providing continuous global land observations for nearly four decades.
The key component in the LDCM project is the development of a mid-resolution, highly calibrated, multispectral imaging radiometer called the Operational Land Imager (OLI), which is being designed and built by Ball Aerospace in Boulder, CO. This series of intercomparison activities will ensure the successful transfer of the radiance scale from NIST in Gaithersburg to the OLI.
SI traceability will be accomplished using an integrating sphere from Ball Aerospace that has been calibrated at the NIST Facility for Automated Spectroradiometric Calibrations (FASCAL) facility. To ensure proper calibration and traceability of the OLI, the sphere was characterized, following its calibration, in a weeklong comparison campaign in February 2010. A set of calibrated transfer radiometers and spectrometers from NIST, NASA Goddard Space Flight Center, Ball Aerospace, and the University of Arizona measured the radiance from the sphere, and these measurements were compared to measurements made from two NIST reference spheres.
Two additional comparison campaigns are planned for the integrating sphere, occurring prior to and following calibration of OLI with the sphere at Ball Aerospace. Analysis of the complete set of measurements will enable characterization of the sphere’s stability over time. This uncertainty will be included in the full uncertainty budget of the OLI instrument.