1 Optical Relative Attitude Sensor for Short-Range Navigation NASA SBIR Contract Number NAS PI: Visidyne / C. Trowbridge

2 Investigate, primarily through modeling, the advantages of a 3-Dimensional imaging sensor for the range and attitude solution required for short-range rendezvous and docking. Unique method of determining range to a scene by synchronously measuring the intensity of modulated laser light backscattered from the scene. Range to markers is a measurement – not derived. Can work with skin return only and the known geometry of the target, but processing would be eased if unique-geometry return-enhancing markers were applied to the target (e.g., retro-reflective tape). Optical Relative Attitude Sensor for Short-Range Navigation

3 Basic concept for intensity modulated light ranging. The detector for 3D imaging is located near the transmitter and records the phase of the intensity modulation scattered from a scene (slide 4).

4 Optical Relative Attitude Sensor for Short-Range Navigation

5 Visidyne has developed 2 synchronous integration focal planes providing demodulation at the focal plane. One was a 3 storage well device which was too slow for practical use. The other was a 2 storage well device sampling 180 degrees apart – this required that 2 consecutive exposures be made 0, 180 degrees and 90, 270 degrees – 4 total samples of the backscattered intensity that were converted to a range and intensity image. Two focal planes and simultaneous exposures could have been used. This device provided acceptable demodulation and range data for 1 MHz modulation (300m wavelength). The shuttered CCD developed by MIT Lincoln Labs (MIT/LL) promises to provide a better solution. While 3 focal planes could be used, MIT/LL scientists feel that a single device with 3 storage wells per pixel and modulation wavelength of 30 meters is practical. Optical Relative Attitude Sensor for Short-Range Navigation