Building Earth Observation Cameras

175Pushbroom Imagers

This is carried out by projecting a uniform light source onto the camera

entrance aperture. The obvious next issue is how to generate a uniform source

of light. The at-sensor nonuniformity in the light input should be much less

than the tolerable mismatch between the pixels after correction. The light source

should ll the total FOV of the camera under test. The test is usually carried out

using a uniform light source, such as an integrating sphere. Since the integrat-

ing sphere performance primarily decides the nal radiometric accuracy, we

shall briey describe the principles of operation of an integrating sphere.

An i