Angular signatures, and a space-borne measurement concept

The nature and value of angular signatures in remote sensing are reviewed with emphasis on the canopy hot-spot as a directionally localized angular signature and an important special case of a BRDF. A new concept is presented that allows hot spot measurements from space by using active (laser) illumination and bistatic detection. The detectors are proposed as imaging array sensors that are circulating the illumination source (or vice versa) and are connected with it through tethers in space which also provide the directional controls needed so that the entire system becomes pointable like a search light. Near infrared or IR operation in an atmospheric transmission window is envisioned with night-time data acquisition. Detailed feasibility and systems analyses have yet to be performed.