21 July 2010 Calibration dome screen for the Large Synoptic Survey Telescope
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Abstract
The Large Synoptic Survey Telescope (LSST) flat-fields must repeatedly trace not only the spatial response variations, but also the chromatic response through the entire optical system, with an accuracy driven by the photometric requirements for the LSST survey data. This places challenging requirements on the LSST Calibration Dome Screen, which must uniformly illuminate the 8.4-meter diameter telescope pupil over its 3.5-degree field of view at desired monochromatic wavelengths in a way that allows the measurement of the total system throughput from entrance pupil to the digitization of charge in the camera electronics. This includes the reflectivity of the mirrors, transmission of the refractive optics and filters, the quantum efficiency of the sensors in the camera, and the gain and linearity of the sensor read-out electronics. The baseline design uses a single tunable laser and includes an array of discrete projectors. The projected flux of light produced by the screen must fill the entire telescope pupil and provide uniform illumination to 1% at the focal plane and to within 0.25% over any optical trajectory within 0.5 degrees of each other. The wavelength of light is tunable across the LSST bandpass from 320 nm to 1080 nm. The screen also includes a broad-band ("white") light source with known Spectral Energy Density (SED) that spans the same range of wavelengths.
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William J. Gressler, Peter Doherty, Victor L. Krabbendam, Ming Liang, Abhijit Saha, Christopher W. Stubbs, Amali Vaz, "Calibration dome screen for the Large Synoptic Survey Telescope", Proc. SPIE 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation, 77391P (21 July 2010); doi: 10.1117/12.857425; https://doi.org/10.1117/12.857425
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