A scanning system combining active and passive detection of radiation from targets. In the active mode, a laser beam is scanned with a rotating wedge in a downward looking Palmer pattern, a portion of the beam is reflected from targets, and coherent detection is performed on the returned signals. Means is disclosed for automatically compensating for misalignment between the signal return beam and local reference beam upon the coherent detector. In the passive mode, infrared radiation inherently emitted by targets is also detected.