Acquisition and Tracking Assembly I

A brassboard laser-beacon and optical tracking subsystem, representative of corresponding portions of a space optical communications subsystem, was built and tested. The objective was to evaluate acquisition, tracking, and pointing capabilities using components feasible for space. A one-way link was...

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Bibliographic Details
Main Authors: Yates, E. C, Chippendale, G. R, Bakke, J. C, Ichiki, S. K, McClellan, C. E
Format: Report
Language:English
Subjects:
ACCURACY
ACQUISITION
AIMING
ATTENUATION
BRASSBOARD MODELS
COMMUNICATION SATELLITES
COMPUTERIZED SIMULATION
CONTINUOUS WAVES
DATA LINKS
GIMBALS
HELIUM
INFRARED BEACONS
INFRARED COMMUNICATIONS
INFRARED IMAGES
INFRARED TELESCOPES
INFRARED TRACKING
LASER COMMUNICATIONS
LASER TRACKING
Lasers and Masers
MIRRORS
NEODYMIUM LASERS
NEON
Optical Detection and Detectors
OPTICAL TRACKING
Q SWITCHING
RADIO TRANSMISSION
SATELLITE COMMUNICATIONS
SPACE COMMUNICATIONS
SYNCHRONOUS SATELLITES
YTTRIUM ALUMINUM GARNET
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Description
Summary:A brassboard laser-beacon and optical tracking subsystem, representative of corresponding portions of a space optical communications subsystem, was built and tested. The objective was to evaluate acquisition, tracking, and pointing capabilities using components feasible for space. A one-way link was established between the beacons from one terminal, and the tracker from a second terminal. Attenuation simulating the space path loss between a low-orbit satellite and a synchronous satellite was introduced. Limit cycle and orbital motions of a satellite were simulated. Six-in. -aperture, off-axis parabolas and representative lasers and detectors were used. A Q-switched Nd: YAG transmitted 20-ns pulses at 1/10-sec intervals for coarse acquisition and a HeNe modulated cw laser was the beacon for fine acquisition and tracking. In coarse acquisition, the pulses were received by quadrant photodetectors. An image-dissector tracker acquired and then tracked the HeNe beacon by means of fine-steering mirrors with a response of 300 Hz and a large gimballed mirror with a 10-Hz response. Overall performance was measured by pointing an HeCd laser from the tracking terminal toward a pointing detector at the beacon terminal. Performance with components operating on space applicable principles and under simulated space, optical and motion conditions was satisfactory. Acquisition times averaged 5.6 sec. Two-axis pointing accuracy, under the predicted signal conditions, was 0.3 microrad rms, somewhat better than the predicted 0.4 microrad rms, or 1/10 of the transmitted bandwidth. Typical peak-to-peak pointing error excursions were about 1.5 microradians. (Author)