Optical Imagers and CCDs for the Gemini Telescopes

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Session 11 -- Gemini, Keck, Seeing
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[11.03] Optical Imagers and CCDs for the Gemini Telescopes

T. Boroson (NOAO/KPNO)

As part of the process for specifying the initial complement of instruments for the Gemini 8-meter telescopes, the Optical Imager Working Group (G. Luppino - chair, T. Boroson, J. Geary, J. Beletic, P. Hickson, M. Irwin) has been given the charge of identifying the scientific and technical requirements for optical imagers and optical focal plane detectors. This group has submitted a report which suggests a number of specifications and goals for the capabilities of scientific imagers, acquisition imagers, spectrograph detectors, and sensors to be used for field acquisition, guiding, and active and adapative correction of optics. The report also includes proposed conceptual designs which will satisfy those requirements.

The proposed scientific imager consists of a CCD mosaic having an overall format of 8192 $\times$ 8192 with 15$\mu$ pixels. In practice, pixels would be binned 2 $\times$ 2 on chip, effectively resulting in a 4096 $\times$ 4096 array with 30$\mu$ pixels. This array has a field of view of 3.3 arcminutes at the f/16 focus and 9 arcminutes at the f/6 focus. This pixel size corresponds to 0.05 arcseconds at f/16 and 0.13 arcseconds at f/6, allowing good sampling of the point spread function in the best seeing conditions. Each of the two mosaics (one for each telescope) would be constructed from eight 2048 $\times$ 4096 format CCDs with a 3-side-buttable configuration. The proposed spectrograph focal plane detectors would be constructed of the same 2048 $\times$ 4096 15$\mu$ pixel CCDs in smaller mosaics. In the case of the multiple object spectrograph, a 4096 $\times$ 4096 array is proposed. For the high resolution optical spectrograph, a T-shaped array which efficiently covers a cross-dispersed echelle format can be made.

This poster presents details of the specifications for the various applications as well as a discussion of related issues including the baffling of the telescopes, atmospheric dispersion correction, and a novel approach to curvature sensors for adaptive optics correction.

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