Optical EngineeringLaser vision system to measure and track the attitude of a tether-stabilized satellite system in a laboratory simulator
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A bidimensional laboratory simulator to measure and control the attitude of a tether-stabilized platform for orbiting telescopes is presented and discussed. Yaw and libration angles are measured by plane tracking of the image of a laser spot, reflected on a screen by a mirror fixed to a floating platform. A multiple-reflection optical lever enables amplification of platform motion. The libration and yaw angles are related to the coordinates of the spot projected on the screen. Disturbances due to overall tether dynamics and telescope slewing are both reproduced and accounted for. Attitude control is achieved by moving the attachment point of the tether on the platform. Displacements are computed and commands are sent to a dc servo-motor via a PC. This measurement system allows platform libration ? and yaw ? angles to be measured to an accuracy of 0.06×10-3 rad; an accuracy of 0.4×10-3 rad in 10 s is reached in attitude control.