Accession Number : AD0918665

Title :   Acquisition and Tracking Assembly I.

Descriptive Note : Final rept. 1 Sep 72-31 Aug 73,

Corporate Author : LOCKHEED MISSILES AND SPACE CO INC PALO ALTO CA PALO ALTO RESEARCH LAB

Personal Author(s) : Yates, E. C. ; Chippendale, G. R. ; Bakke, J. C. ; Ichiki, S. K. ; McClellan, C. E.

Report Date : 26 OCT 1973

Pagination or Media Count : 295

Abstract : 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)

Descriptors :   *SPACE COMMUNICATIONS), (*LASER COMMUNICATIONS, (*COMMUNICATION SATELLITES, SATELLITE COMMUNICATIONS), (*NEODYMIUM LASERS, LASER TRACKING), RADIO TRANSMISSION, INFRARED BEACONS, AIMING, OPTICAL TRACKING, ATTENUATION, SYNCHRONOUS SATELLITES, INFRARED TELESCOPES, Q SWITCHING, INFRARED TRACKING, ACQUISITION, INFRARED COMMUNICATIONS, YTTRIUM ALUMINUM GARNET, GIMBALS, HELIUM, NEON, CONTINUOUS WAVES, MIRRORS, DATA LINKS, COMPUTERIZED SIMULATION, INFRARED IMAGES, ACCURACY, BRASSBOARD MODELS.

Subject Categories : Lasers and Masers
      Optical Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE