The Defense Meteorological Satellite Program (DMSP) is currently scheduled to launch the first of five Special Sensor Microwave Imager/Sounder (SSMIS) in October 2002. The SSMIS is a joint United States Air Force/Navy multi-channel passive microwave sensor that combines and extends the current imaging and sounding capabilities of three separate DMSP microwave sensors, SSM/T, SSM/T-2 and SSM/I. Built by Aerojet, the SSMIS measures the earth’s upwelling partially-polarized radiances in 24 channels covering a wide range of frequencies (19 – 183 GHz) in an SSM/I-type conical scan geometry (53 degree earth incidence angle), maintaining uniform spatial resolution, polarization purity and common fields-of-view for all channels across the entire swath. The SSMIS Upper Atmosphere Sounding (UAS) offers a unique opportunity to provide real-time stratospheric and mesospheric temperature observations. This capability requires that the SSMIS measure radiation with filter bandwidths < 1.5 MHz centered on four O2 resonance lines in the 60 to 65 GHz frequency range. Due to the narrowness of these filters, the system must correct for the Doppler shift in the passive radiation due to the motion of the satellite and the conical scan geometry of the sensor. This onboard correction will be validated during initial instrument check-out using the methodology described in this paper. A comprehensive end-to-end calibration/validation (Cal/Val) of the first SSMIS is planned to begin shortly after launch. However, supporting measurements for the calibration and validation of the retrieved upper air soundings are quite limited in comparison to tropospheric and lower stratospheric sounding sensors. A wide reaching combination of lidar, rocketsonde and NWP model fields will be used to calibrate the SSMIS UAS channels and retrieved temperature profiles. Plans for the utilization of these data sources and their limitations will be presented.