The Special Sensor Microwave Imager (SSM/I) flies aboard the F8, F10, F11, F13, F14, F15, F16, and 17 polar-orbiting satellite platforms of the Defense Meteorological Satellite Program; it is designated SSM/IS on the F16 and F17 platforms due to the additional sounding capability of the instrument. The primary mission of the SSM/I is to support the Department of Defense (DoD) operations, and the release of SSM/I data to the science community is on behalf of DoD support. The SSM/I is a seven-channel, four-frequency, orthogonally polarized, passive microwave radiometric sensor system that measures atmospheric, ocean and terrain microwave brightness temperatures at 19.35, 22.2, 37.0, and 85.5 GHz.The SSM/I rotates continuously about an axis parallel to the local spacecraft vertical at 31.6 rpm and measures the upwelling scene brightness temperature over an angular range of 102.4 degrees about the sub-satellite (i.e. nadir) track. The absolute brightness temperature of the scene incident upon the antenna is received and spatially filtered by the antenna to produce an effective input signal or antenna temperature at the input of the feed horn antenna.
SSM/I can be used to measure calibrated geophysical parameters of ocean wind speed, atmospheric water vapor, cloud liquid water, and rain rate (Wentz 1997; Wentz and Spencer, 1998). More recent methods have provided for the possibility of derived retrievals of near-surface air temperature and specific humidity (Roberts et al. 2010).
Since SSM/I can only resolve the wind speed magnitude, recent efforts have been made to assign NWP-derived wind directions using a variational analysis method (Atlas et al. 1996; Atlas et al. 2011). Atlas et al. (1996, 2011) has assimilated cross-calibrated SSM/I data, along with other cross-calibrated passive and active microwave sensor data into a gridded ocean surface wind vector analysis product known as the Cross-Calibrated Multi-Platform (CCMP) Ocean Surface Wind Velocity Analyses, which are available through the PO.DAAC: ftp://podaac-ftp.jpl.nasa.gov/allData/ccmp
Additional SSM/I data, albeit obsolete by current calibration standards, are also available through the PO.DAAC:ftp://podaac-ftp.jpl.nasa.gov/allData/ssmi/retired/
The most up-to-date SSM/I data may be obtained directly through Remote Sensing Systems (REMSS):http://www.remss.com/ssmi/