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Proceedings Paper

Two-color laser ranging to a cooperative airborne target
Author(s): Jan F. McGarry; John W. Cheek; Pamela Seville Millar; James B. Abshire
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Paper Abstract

An experiment was performed during the summer of 1992 to measure the changes in the roundtrip time of flight of laser light due to horizontal gradients in the atmosphere. Dual laser frequencies were used to range from a fixed telescope ground system to an array of corner cubes mounted on an aircraft. The aircraft flew circular paths at slant ranges of 20 to 25 kilometers around the ground facility. To maximize the number of two color returns from the aircraft, both an acquisition and a closed loop tracking scheme were developed. A Global Positioning System (GPS) receiver placed onboard the aircraft relayed its position to the ground via a radio downlink; when this data was extrapolated in time, it gave telescope acquisition pointing angles to within 1 degree of truth. Closed loop tracking was then achieved by digitizing the image of a down-looking infra-red beacon which was viewed through a camera mounted on the telescope. The X-Y coordinates of the beacon in the camera field of view were sent to the telescope computer to continuously track the image. Stable tracking was achieved on each of the three experiment nights for over 90 minutes with tracking errors within the required 200 microradian limit. Enough two color waveform data was obtained to analyze the horizontal changes in the atmospheric delay.

Paper Details

Date Published: 1 October 1993
PDF: 12 pages
Proc. SPIE 1950, Acquisition, Tracking, and Pointing VII, (1 October 1993); doi: 10.1117/12.156609
Show Author Affiliations
Jan F. McGarry, NASA Goddard Space Flight Ctr. (United States)
John W. Cheek, NASA Goddard Space Flight Ctr. (United States)
Pamela Seville Millar, NASA Goddard Space Flight Ctr. (United States)
James B. Abshire, NASA Goddard Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 1950:
Acquisition, Tracking, and Pointing VII
Michael K. Masten; Larry A. Stockum, Editor(s)

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