1 October 1993 Medium accuracy pointing system for attached payloads
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The pointing system described in this paper was originally developed as part of the Hard X-ray Imaging Telescope (XRT) built by the University of Birmingham for flight on the Spacelab-2 mission in 1985. The primary scientific objective of the XRT was the imaging of extended celestial X-ray sources in the energy band 2.5 - 30 kev using the coded-aperture technique. In order to maximize the observing time available to the XRT the instrument was provided with an independent pointing mount. The performance parameters of the pointing system were determined by the requirements of the XRT and resulted in the development of a two- axis gimbal system capable of supporting a moving mass of 280 kg and providing an inertial pointing stability of 20'. The mechanical configuration of a balanced payload with gimbal support bearings rated to withstand the launch environment without off-loading was chosen to enhance reliability and minimize development costs. The electrical configuration is based around duel redundant torque motors and synchros on each axis. The control loop is closed via redundant Intersil IM6100 microprocessors. The control software uses a novel algorithm to estimate gimbal rates from timing transition data from the synchros.
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Christopher James Eyles, Christopher James Eyles, Gerald K. Skinner, Gerald K. Skinner, A. P. Willmore, A. P. Willmore, } "Medium accuracy pointing system for attached payloads", Proc. SPIE 1950, Acquisition, Tracking, and Pointing VII, (1 October 1993); doi: 10.1117/12.156613; https://doi.org/10.1117/12.156613


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