Recent advances in calibration of the GOES Imager visible channel at NOAA

To track the degradation of the Imager visible channel on board NOAA's Geostationary Operation Environmental Satellite (GOES), a research program has been developed using the stellar observations obtained for the purpose of instrument navigation. For monitoring the responsivity of the visible channel, we use observations of approximately fifty stars for each Imager. The degradation of the responsivity is estimated from a single time series based on 30-day averages of the normalized signals from all the stars. Referencing the 30-day averages to the first averaged period of operation, we are able to compute a relative calibration coefficient relative to the first period. Coupling this calibration coefficient with a GOES-MODIS intercalibration technique allows a direct comparison of the star-based relative GOES calibration to a MODIS-based absolute GOES calibration, thus translating the relative star-based calibration to an absolute star-based calibration. We conclude with a discussion of the accuracy of the intercalibrated GOES Imager visible channel radiance measurements.