SSMIS LOWER ATMOSPHERIC SOUNDING CAL/VAL

This report describes calibration of the DMSP Special Sensor Microwave Imager Sounder (SSMIS) Lower Atmospheric Sounding (LAS) channels. SSMIS, shown in Figure 1, is a conically scanning microwave imager/sounder. It combines the functionality of SSM/I together with a number of new sounding features providing vastly increased altitude coverage, based on new 60 GHz oxygen channels for mesospheric temperature profiling. The conical scan geometry provides uniform imaging and weighting functions (Figure 2), as opposed to varying weighting functions and polarization for conventional cross-track instruments. Higher spatial resolution, relative to SSM/T-1 and SSM/T-2, is available in sounding channels. The 19-92 GHz surface channels functionally duplicate SSM/I and the instrument architecture resembles SSM/I. The moisture channel frequencies coincide with SSM/T-2. The instrument body and main reflector rotate together and the reflector is external to warm load and cold sky calibration pathways. Many aspects of calibration will be discussed elsewhere. These include calibration of SSM/I-related channels (12-18) and Upper Atmsopheric Sounding (UAS) channels (19-24). Extensive efforts performed by NRL led to high quality data for SSM/I-related imaging channels. Those efforts also included readjust________________________________ Corresponding author: john.e.wessel@aero.org ment of geolocation parameters and improvement of antenna pattern corrections.