The  Tropical Rainfall Measuring Mission
                        (TRMM) http://disc.sci.gsfc.nasa.gov/precipitation/secondary/instruments/trmm_instr.shtml/  is a joint
                        U.S.-Japan   satellite mission to monitor tropical and subtropical
                        precipitation and to estimate its associated latent heating. 
                        
                        The Level 1B product file (1B11) contains calibrated brightness
                        temperatures and auxiliary geolocation information for each
                        pixel in the scan. The structure of the Level 1B data file is based
                        on the Wentz format for the SSM/I data. The Level 1B data are stored
                        in the Hierarchical Data Format (HDF), which includes both core and
                        product specific metadata applicable to the TMI measurements. A file
                        contains a single orbit of data with a file size of about 14 MB
                        (uncompressed). The HDF-EOS &quot;swath&quot; structure is used to accommodate
                        the actual geophysical data arrays. As in the case of the Level 1A
                        data, there are 16 files of TMI 1B11 data produced per day.
                        
                        Antenna temperatures are derived from the Level 1A sensor counts by
                        applying a linear relationship of the form: Tb = a + b * count. The
                        resultant temperatures are corrected for cross-polarization and
                        spill-over to produce the brightness temperatures found in the Level
                        1B product.  However, no antenna beam pattern correction or
                        sample-to-pixel averaging has been applied to these brightness
                        temperatures.
                        
                        In the Level 1B data, geolocation and channel data are written out for
                        each pixel along the scan, whereas the time stamp, scan status
                        (containing scan quality information), navigation, calibration
                        coefficients, and satellite zenith angle are specified on a per-scan
                        basis. There are, in general, 2991 scans along the orbit, with each scan
                        consisting of 208 high resolution (85 GHz) pixels, and 104 low
                        resolution pixels (all other channels). The scan width is about 760
                        km.
                        
                        Spatial coverage is between 38 degrees North and 38 degrees South
                        owing to the 35 degree inclination of the TRMM satellite. This orbit
                        provides extensive coverage in the tropics and allows each location to
                        be covered at a different local time each day, enabling the analysis
                        of the diurnal cycle of precipitation.