Validation of NOAA-21 VIIRS TEB response versus scan angle determined from measurements during the spacecraft pitch maneuver

VIIRS is a key instrument on board the Suomi National Polar-orbiting Partnership and NOAA-20 satellites, launched in October 2011 and November 2017, respectively. The third VIIRS in the series carried on the NOAA-21 satellite was recently launched in November 2022. The quality of the VIIRS response versus scan angle (RVS) characterization is vitally important to ensure there is consistent calibration across the entire scan range. The RVS was characterized prelaunch in lab ambient conditions and is currently used to calibrate the on-orbit response for all scan angles. A spacecraft level pitch maneuver is typically scheduled during the initial intensive Cal/Val testing after launch and provides a rare opportunity for VIIRS to conduct observations of deep space over the entire scan range, which can be used to characterize the RVS for the thermal emissive bands (TEB). This study provides analysis of the NOAA-21 pitch maneuver data and methodology to determine the VIIRS TEB RVS. A comparison of the RVS results determined from the pitch maneuver observations and those from prelaunch lab measurements is provided for each band, detector, and mirror side of the half angle mirror. Comparison of biases in brightness temperature as a function of scan angle is also conducted by inter-comparing with co-located Cross-Track Infrared Sounder (CrIS) on the NOAA-21 satellite to examine the RVS stability in reference to CrIS.