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20 August 1986 Control And Alignment Of The Hubble Space Telescope
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The optics within the Hubble Space Telescope consist essentially of a primary and secondary mirror. Measurements from three wavefront sensors are telemetered to the ground where a series of computations are made to determine whether the telescope is performing within specifications. If not, optimum secondary mirror realignment parameters are computed based on the aberrations present in the wavefront. The mirror support structure is held at three places by six links. Position adjustment is made by independently extending or withdrawing each of the links. These six actuators are small angular motion stepping motor drives with eccentric output shafts. Rotation of the shaft produces a displacement of the link as a function of the actuator shaft angle. The angle is determined from the output of a potentiometer coupled to the actuator output shaft or by counting the number of steps taken since launch. This paper presents a mathematical analysis of the secondary mirror control structure. It describes a geometrical model which permits a calculation of all six actuator positions given the position of the secondary mirror, and the calculation of the secondary mirror position, given the angular position of the six secondary mirror actuators. A series of tests for validating the model is described. In these tests mirror positions predicted by the model were compared with actual positions measured by test instrumentation. These tests demonstrate conclusively that the mirror can be accurately positioned within require-ments in a few iterations.
© (1986) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Louis D. Grey "Control And Alignment Of The Hubble Space Telescope", Proc. SPIE 0628, Advanced Technology Optical Telescopes III, (20 August 1986);


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