29 September 2004 LSST mirror thermal performance
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Abstract
The proposed science missions of the LSST require a telescope with an optical etendue of greater than 250 meters square degrees square. The current LSST Baseline Configuration has a field of view of 3.5 degrees and an optical etendue of 302 m2d2. The etendue calculation includes the effect of gradual vignetting by the camera as the field angle increases. A current optical point design includes spun cast light-weighted borosilicate mirrors (primary and tertiary) of 8.4 and 5 m diameter respectively. Thermal control systems are needed to optimize telescope seeing and to minimize the thermal distortion of the mirrors. The goals of this study are to determine the airflow requirements for the specified ambient temperature rate of change, to identify thermal time constants and to predict the magnitude and form of thermal distortions that can be developed by environmental conditions. Operational data taken at the 6.5 m MMT (Multi-Mirror Telescope Observatory) and at the Magellan Observatory are presented for comparison with this study. Finally, the results from the thermal analysis were used to simulate the LSST focus control over one night of observation and to estimate the effect on the image quality for different correction frequencies.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Brian Cuerden, Jacques Sebag, Steve West, "LSST mirror thermal performance", Proc. SPIE 5495, Astronomical Structures and Mechanisms Technology, (29 September 2004); doi: 10.1117/12.550641; https://doi.org/10.1117/12.550641
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KEYWORDS
Mirrors

Telescopes

Large Synoptic Survey Telescope

Distortion

Observatories

Temperature metrology

Cameras

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