Optical Relative Attitude Sensor for Short-Range Navigation
NASA SBIR
Contract Number NAS9-01161
PI: Visidyne / C. Trowbridge
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Optical Relative Attitude Sensor for Short-Range Navigation
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).
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Optical Relative Attitude Sensor for Short-Range Navigation
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).
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Optical Relative Attitude Sensor for Short-Range Navigation
01-111
RF SOURCE
D
A
TRANSMITTER
WITH LD ARRAY
A
12
, Z, X, Y
T(I)
12
I, X, Y
L
3-PHASED
IMAGES
 = 2Z/ 
OUTGOING
WAVE FRONT
R(I)
S(I)
A
L
VISIDYNES PHASE,
MAGNITUDE
PROCESSOR
RECEIVER WITH
3 - FPA
~
SHAPED,
DISTORTED
RETURN
WAVE FRONT
 = c/fm
TARGET
SATELLITE
Possible Configuration
for Retroreflective
Targets for Docking
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Optical Relative Attitude Sensor for Short-Range Navigation
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.
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