The constant scan angle for the SSM/I channels has several clear advantages for generating derived products. Many microwave product algorithms depend upon a priori estimates of surface emissivity. Emissivity is difficult and often impossible to accurately specify particularly over land. A varying scan angle makes emissivity estimation even more difficult since surface emissivity in the microwave may vary strongly as a function of viewing angle.

A constant viewing angle simplifies computations of atmospheric temperature, moisture, and precipitation. These quantities depend upon the distance (path length) that the microwave radiation travels before reaching the satellite. A changing viewing angle results in a corresponding change in path length and must therefore be factored into the product computations as is the case for AMSU.