B. Special Sensor Microwave Imager (SSMI)

The SSMI is a conical-scanning, multi-channel, multi-polarization microwave radiometer aboard DMSP spacecraft. The SSMI can be seen in figures 2 and 3. Figure 2 shows the sensor by itself, and figure 3 shows where the sensor is located on the bus (or structure ) of the satellite.

Air Force Weather Agency SSM/I  Training

Figure 2

Air Force Weather Agency SSM/I  Training

Figure 3

As demonstrated in figure 4, the sensor rotates axially through 360 degrees. However, it only actually scans through 102 degrees of the rotation in the back of the satellite. This is because of (1) an electronic need to recalibrate the SSMI every time around, and (2) because of an unavoidable physical obstruction to the sensors' field of view caused by the bus of the spacecraft itself. This 102 degree limitation is important because it cuts down the amount of area the sensor could cover ( SSMI has half the spatial coverage of the DMSP OLS). 
Air Force Global Weather Central SSM/I  Training

Figure 4 

Image provided by Hughes Information Technology Corp. (HITC)

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