ABSTRACT

We present the design, construction, and performance of SpeX, a medium‐resolution 0.8–5.5 μm cryogenic spectrograph and imager, now in operation at the 3.0 m NASA Infrared Telescope Facility (IRTF) on Mauna Kea. The design uses prism cross‐dispersers and gratings to provide resolving powers up to simultaneously across 0.8–2.4, 1.9–4.2, or 2.4–5.5 μm, with a 15 long slit. A high‐throughput low‐resolution prism mode is also provided for faint‐object and occultation spectroscopy. Single‐order 60 long‐slit modes with resolving powers up to are available for extended objects. The spectrograph employs an Aladdin 3 InSb array and uses narrow slits and a spatial scale of 0 15 pixel for optimum sensitivity on point sources. An autonomous infrared slit viewer is used for object acquisition, infrared guiding, and scientific imaging in the wavelength range 0.8–5.5 μm. The imager employs an Aladdin 2 InSb array that covers a field of view at 0 12 pixel . SpeX was successfully commissioned on IRTF during 2000 May, June, and July. Astronomical observations are presented to illustrate performance.