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Gemini Telescope

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On Gemini, science instruments are mounted at the cassegrain focus below the 8.2 meter primary mirror. The picture below shows a schematic of the telescope and specifically the bottom end where instruments are mounted. The f/16 telescope beam passes through the 1.18 meter diameter central primary hole, through the Acquisition & Guide Unit (the A&G, where the peripheral wavefront sensors and guide camera are located), and is directed to one of the science instrument ports via a science fold mirror.

[Gemini Telescope]

The photo below shows the Instrument Support Structure (ISS) with ballast weights located on the bottom end of the telescope. Up to four science instruments can mount simultaneously within this structure. It will be possible to mount NIRI on either a side-looking or upward looking port, the latter being preferred for 3-5um thermal IR observations to minimize the number of reflective surfaces encountered by the telescope beam and hence the thermal IR background.

[Gemini ISS]

Below is a photo of NIRI mounted on the up-looking port of the ISS on Gemini North.

[NIRI on Gemini]

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Last update August 15, 2000; Colin Aspin

Gemini Observatory Participants