Coarse pointing assembly for the SILEX program, or how to achieve outstanding pointing accuracy with simple hardware associated with consistent control laws

Daniel Buvat; Gerard Muller; Patrick Peyrot

doi:10.1117/12.43758

1 June 1991 Coarse pointing assembly for the SILEX program, or how to achieve outstanding pointing accuracy with simple hardware associated with consistent control laws

Daniel Buvat, Gerard Muller, Patrick Peyrot

Author Affiliations +

Proceedings Volume 1417, Free-Space Laser Communication Technologies III; (1991) https://doi.org/10.1117/12.43758
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

Attention is given to the coarse pointing assembly (CPA) for the SILEX program, designed on the basis of 10 years of MATRA experience in very accurate drive mechanisms successfully conducted by the SPOT 1 and 2 flights as well as EURECA IOC. The basic key design feature of the mechanism is a 1200-step stepper motor driven in microstepping with harmonic defects compensation. This allows very low torque noise associated with a high accuracy (0.01 deg). The direct drive principle avoids backlash and permits a linear control of the output shaft of each drive. The only parts susceptible to possible wear are the ball bearings, which have a design margin of greater than 1000 for 10 yr of service life. In order to meet the dynamic performances required by SILEX, a closed loop active damping system is added to each drive unit. Two accelerometers used in a differential way sense the hinge microvibrations and an active damping loop reduces their Q factor down to a few dB. All CPA electrical parts (including motor, optical encoder, and accelerometer) are redundant to avoid single point of failure.

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Daniel Buvat, Gerard Muller, and Patrick Peyrot "Coarse pointing assembly for the SILEX program, or how to achieve outstanding pointing accuracy with simple hardware associated with consistent control laws", Proc. SPIE 1417, Free-Space Laser Communication Technologies III, (1 June 1991); https://doi.org/10.1117/12.43758

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