Reconnaisance Satellites

whiskbroom vs. pushbroom scanning:

Whiskbroom scanners sweep laterally across the satellite's track; pushbroom scanners capture a whole line across the track at once. Whiskbroom scanners use a single sensor, so there's not problem with calibration, but the scanning mirrors add complexity. Pushbroom scanners use multiple sensors, which need to be calibrated, but don't have the added complexity of scanning mirrors.