S-NPP advanced technology microwave sounder: Reflector emissivity model, mitigation, & verification

The Suomi NPP spacecraft pitchover maneuver revealed an ATMS scan angle-dependent bias when viewing deep space, which is a homogenous and unpolarized source that fills the entire ATMS Field of Regard. Reflector emissivity was investigated as a possible root cause. The emissivity is polarization dependent, which results in a scan-dependent bias with the quasi-vertical channels having a different bias shape than the quasi-horizontal channels. The normal emissivity was empirically estimated by minimizing the scan bias during the pitchover maneuver, and the reflector´s temperature was derived from ATMS telemetry. The model, calibration change, and estimated normal emissivity were verified using the ATMS thermal vacuum test data. Reflector emissitivies from approximately 0.2% to 0.4% were derived, resulting in brightness temperature corrections of up to 0.5 K.