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Proceedings Paper

Characterization and design of digital pointing subsystem for optical communication demonstrator
Author(s): Caroline S. Racho; Angel Portillo
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Paper Abstract

The Optical Communications Demonstrator (OCD) is a laboratory- based lasercom demonstration terminal designed to validate several key technologies, including beacon acquisition, high bandwidth tracking, precision beam pointing, and point-ahead compensation functions. It has been under active development over the past few years. The instrument uses a CCD array detector for both spatial acquisition and high-bandwidth tracking, and a fiber coupled laser transmitter. The array detector tracking concept provides wide field-of-view acquisition and permits effective platform jitter compensation and point-ahead control using only one steering mirror. This paper describes the detailed design and characterization of the digital control loop system which includes the Fast Steering Mirror (FSM), the CCD image tracker, and the associated electronics. The objective of this work is to improve the overall system performance using laboratory measured data. The design of the digital control loop is based on a linear time invariant open loop model. The closed loop performance is predicted using the theoretical model. With the digital filter programmed into the OCD control software, data is collected to verify the predictions. This paper presents the results of the system modeling and performance analysis. It has been shown that measurement data closely matches theoretical predictions. An important part of the laser communication experiment is the ability of FSM to track the laser beacon within the required tolerances. The pointing must be maintained to an accuracy that is much smaller than the transmit signal beamwidth. For an earth orbit distance, the system must be able to track the receiving station to within a few microradians. The failure to do so will result in a severely degraded system performance.

Paper Details

Date Published: 26 April 1999
PDF: 12 pages
Proc. SPIE 3615, Free-Space Laser Communication Technologies XI, (26 April 1999); doi: 10.1117/12.346186
Show Author Affiliations
Caroline S. Racho, Jet Propulsion Lab. (United States)
Angel Portillo, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 3615:
Free-Space Laser Communication Technologies XI
G. Stephen Mecherle, Editor(s)

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