Pardon me for sending two messages on this, but I just found this, and it has more detail: http://eosdis.larc.nasa.gov:12000/sensor_documents/ssmi_sensor.html > 3. Instrument Layout, Design, and Measurement Geometry: > > List of Sensors: > > Passive Microwave Radiometer > > Sensor Descriptions: ... > The SSM/I rotates continuously about an axis parallel to the local spacecraft > vertical at 31.6 rpm .... The scan direction is from the left to the right > when looking in the forward (F10,F11) or aft(F8) direction of the spacecraft > with the active scene measurements lying 151.2 deg about the forward (F10,F11) > or aft (F8) direction. This results in a swath width of approximately 1400 km. > The spin rate provides a period of 1.9 sec during which the spacecraft sub- > satellite point travels 12.5 km. Slight discrepancy -- this says 31.6 rpm (1.8987 sec/rotation), while the other document said 31.9 (1.8807 sec). I presume that one of them is a typo. Ed Cannon Austin, Texas, USA 30.3086N, 97.7279W, 165m