Drive-Control System for the TACTIC Gamma-Ray Telescope |
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| Authors: | A K Tickoo R Koul S K Kaul I K Kaul C L Bhat N G Bhatt M K Kothari H C Goyal N K Agarwal S R Kaul |
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| Institution: | (1) Nuclear Research Laboratory, Bhabha Atomic Research Centre, Mumbai, 400 085, India |
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| Abstract: | A PC-based drive-control system has been developed for the altitude-azimuth mounted TACTIC  -ray telescope to control the speed and direction of motion of its 2-axes. Details of various hardware components chosen for the telescope, including hybrid-stepper motor, 16-bit absolute encoder and CAMAC-based programmable stepper motor controller, are discussed in this paper. The telescope-control strategy, based on the position-loop with a proportional type control for the source-seek mode and the on/off type control for the tracking mode, is explained in detail. Some important performance features of the telescope, including its blind-spot size, drive-system backlash and encoder-error compensation, are also presented. The drive system has been extensively field-tested and has been operating satisfactorily during observation campaigns carried out since March 1997 with the TACTIC Imaging Element. A tracking accuracy of ±3 arc-minutes has been achieved. A test report of its performance, with regard to its tracking accuracy on the basis of successful detection of TeV -rays from the active galaxy Markarian 501 in April–May 1997, is also presented. |
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| Keywords: | altitude-azimuth mounting gamma-ray astronomy TACTIC drive-control system |
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