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NIRI Introduction

NIRI, Gemini's Near InfraRed Imager and spectrograph, was built by the University of Hawaii's Institute for Astronomy. NIRI's observing modes are briefly described below.

NIRI has three cameras (f/32, f/14, and f/6) to provide a range of imaging and spectroscopic options. The 1024x1024-pixel ALADDIN InSb array is sensitive from 1 to 5 microns. In imaging mode the cameras provide 0.022, 0.050, and 0.117 arcsec pixels, respectively and fields of view of 22x22, 51x51, and 120x120 arcseconds squared, respectively.

A large number of broad- and narrow-band filters are available (not all filters have arrived or are installed, so please consult the filters web page for availability). Imaging with all cameras and all filters is possible, with the exceptions of the L' band at f/6 and the M band at f/6 and f/14, where the background saturates the array in the minimum exposure time.

At f/6 a set of KRS5 grisms is available to provide moderate-resolution long-slit spectroscopic coverage over almost the entire 1.0-5.5um region.

The Gemini facility adaptive optics system (ALTAIR), is available for use with NIRI at f/14 or f/32, for all imaging except in the M band. Three grisms covering 1.05-2.41um at f/32 at moderate resolution are also available for use with ALTAIR.

For automated guiding without AO, either of the peripheral wavefront sensors are available. They are usable in a number of optical bands and in a 5' to 7' annulus at f/6 (smaller inner diameters for larger f numbers and sometimes as close as 4.25' for f/6 spectroscopy) centered on the target. Note that they can be employed not only to provide guiding, but also to maintain focus and to correct the figure of the primary mirror while observing. The wavefront sensors have proven to be entirely satisfactory for imaging stability and for maintaining point sources in the narrow NIRI slits for up to one hour without pointing adjustments. Magnitude limits for guide stars can be found on the PWFS web pages, although in general observers should select the brightest guide star available.

Phase II observing programs are created using the Observing Tool (OT). To get started, please refer to the OT Tutorial. Examples of typical NIRI observations can be "fetched" from the database using the Observing Tool - the library file is in the "Other" OT programs. The NIRI library xml file also can be downloaded. For more information on preparing Phase II programs, see the Special Instructions page.

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Last update 2006 September 1; Andrew Stephens, Tom Geballe & Joe Jensen