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27 June 2006 Auto alignment and image tracking system for the SUNRISE telescope
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The 1m balloon-borne solar telescope Sunrise will be equipped with a wave-front sensing system for automatic in-flight focusing and alignment of the telescope and for high-precision image tracking. A six-element wavefront sensor measures low order aberrations of the telescope, including defocus and coma. The correction is achieved by moving the focusing mirror and the telescope secondary, respectively, in a closed-loop circuit. The same system measures image motion. The instrument requirements for the tracking are a dynamical range of about 30 Hz and a precision of about 0.005 arcs in the sky. The image motion signal feeds a closed-loop control system that drives both the tip-tilt mirror assembly and the mirrors that are needed for focusing and alignment. The tip-tilt unit is a dual-stage system, built at the Kiepenheuer-Insitut, consisting of a slow component with a large range of about 60 arcs and a fast component with a short range and high bandwidth. A breadboard-version of the Correlating Wavefront Sensor has been successfully tested at the German Vacuum Tower Telescope on Tenerife in summer of 2005. A closed-loop bandwidth of 80 Hz was measured for the tracking system. The wave-front sensor detected image aberrations pre-set by the telescope's adaptive optics system with the required accuracy. Sunrise will be flown in long duration stratospheric balloon flights, with a first scientific flight in 2009.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
W. Schmidt, T. Berkefeld, B. Feger, R. Friedlein, K. Gerber, F. Heidecke, T. Kentischer, O. v. d. Lühe, M. Sigwarth, D. Soltau, and E. Wälde "Auto alignment and image tracking system for the SUNRISE telescope", Proc. SPIE 6274, Advanced Software and Control for Astronomy, 62740H (27 June 2006);


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