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4 August 2010 LSST camera heat requirements using CFD and thermal seeing modeling
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The LSST camera is located above the LSST primary/tertiary mirror and in front of the secondary mirror in the shadow of its central obscuration. Due to this position within the optical path, heat released from the camera has a potential impact on the seeing degradation that is larger than traditionally estimated for Cassegrain or Nasmyth telescope configurations. This paper presents the results of thermal seeing modeling combined with Computational Fluid Dynamics (CFD) analyzes to define the thermal requirements on the LSST camera. Camera power output fluxes are applied to the CFD model as boundary conditions to calculate the steady-state temperature distribution on the camera and the air inside the enclosure. Using a previously presented post-processing analysis to calculate the optical seeing based on the mechanical turbulence and temperature variations along the optical path, the optical performance resulting from the seeing is determined. The CFD simulations are repeated for different wind speeds and orientations to identify the worst case scenario and generate an estimate of seeing contribution as a function of camera-air temperature difference. Finally, after comparing with the corresponding error budget term, a maximum allowable temperature for the camera is selected.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jacques Sebag and Konstantinos Vogiatzis "LSST camera heat requirements using CFD and thermal seeing modeling", Proc. SPIE 7738, Modeling, Systems Engineering, and Project Management for Astronomy IV, 77380D (4 August 2010);


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