ABSTRACT. This paper presents the basic design of the Gemini Near-Infrared Imager (NIRI) and discusses its capabilities. NIRI offers three different pixel scales to match different operating modes of the Gemini telescope and allows polarimetric and spectroscopic observations. It is equipped with an infrared on-instrument wave-front sensor (OIWFS) to allow tip-tilt and focus correction even in highly obscured regions. The science detector array is an Aladdin II InSb pixel device sensitive from 1.0 to 5.5 mm. 1024 # 1024

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The University of Hawaii Near-Infrared Camera is equipped with a NICMOS-3 HgCdTe detector array sensitive from -1 to 2.5 ¡im and produced by the Rockwell International Science Center for the Near-Infrared Camera and Multi-Object Spectrometer Project (NICMOS). In our camera, the NICMOS-3 array operates with 53 electrons readnoise in a double-correlated sampling mode. A dark current below 1 electron per second at an operating temperature of 60 K has been achieved. The device works linearly within 1% up to 250 000 electrons at 1.0 V bias. Techniques for further reduction of readnoise and dark current are discussed. The only significant remaining problem is a residual excess dark current, remaining from previous exposure of the device.

KSPEC (Af-band spectrograph) is an infrared spectrograph designed primarily for spectroscopy in the 2.0-2.5 fim region. It offers two different optical configurations. The first is a cross-dispersed echelle mode designed to cover the atmospheric windows from 1-2.5 fim in one spectral frame of a 256x256 format on a NICMOS-3 HgCdTe detector array. This configuration of the spectrograph provides medium spectral resolution (A/AA~500) for spectral classification work, emission-line detection, and redshift measurements. Alternatively, KSPEC can be equipped with a different spectrograph camera, giving a long-slit, single-order spectrum from 2.05-2.35 fim. The instrument uses a second NICMOS-3 infrared detector array for slit viewing, to facilitate the acquisition of optically invisible objects, to document the slit position, and to monitor it during long spectroscopic integrations. KSPEC does not contain any moving components, making it a very reliable, relatively low-cost instrument that is easy to use.

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