On-Orbit Characterization of S-NPP VIIRS Transmission Functions

The Suomi National Polar-orbiting Partnership (S-NPP) spacecraft executed a series of yaw maneuvers on February 15 and 16, 2012. Data collected during these maneuvers were used to characterize the transmission functions of the Visible Infrared Imager Radiometer Suite (VIIRS) instrument solar diffuser (SD) and solar diffuser stability monitor (SDSM) views. On orbit, only the product of the attenuation screen transmittance and SD bidirectional reflectance distribution function (BRDF) can be measured for the VIIRS detector and SDSM SD views. For the SDSM solar view, the attenuation screen transmittance was also measured. The angular sampling provided by the yaw maneuver data of this solar view was too coarse to capture the fine structure of the transmission function; a model was developed to include this structure in the vignetting function by combining solar observation data from the first nine months of the mission with the yaw maneuver-derived vignetting function. The derived transmission functions were delivered for implementation in the operational processing stream (the derived VIIRS detector view transmittance produced up to 0.4% difference in the instrument responsivity, and SDSM transmission functions impacted the BRDF tracking by up to 3.0%). An uncertainty analysis was also conducted on all transmission functions delivered.