Operational calibration of Geostationary Operational Environmental Satellite-8 and -9 imagers and sounders

TLDR

The paper details the operational in‑orbit calibration of GOES‑8 and GOES‑9 imagers and sounders. Calibration is performed by observing space and an onboard blackbody, fitting a quadratic radiance equation, filtering slopes to reduce noise, correcting for scan‑mirror reflectance variations, normalizing visible channels, and providing a procedure to convert GVAR counts to radiances, temperatures, and mode‑A counts. The result is that users receive scaled radiances in a GOES variable format (GVAR) data stream.

Abstract

We describe the operational in-orbit calibration of the Geostationary Operational Environmental Satellite (GOES)-8 and-9 imagers and sounders. In the infrared channels the calibration is based on observations of space and an onboard blackbody. The calibration equation expresses radiance as a quadratic in instrument output. To suppress noise in the blackbody sequences, we filter the calibration slopes. The calibration equation also accounts for an unwanted variation of the reflectances of the instruments' scan mirrors with east-west scan position, which was not discovered until the instruments were in orbit. The visible channels are not calibrated, but the observations are provided relative to the level of space and are normalized to minimize east-west striping in the images. Users receive scaled radiances in a GOES variable format (GVAR) data stream. We describe the procedure users can apply to transform GVAR counts into radiances, temperatures, and mode-A counts.