SpeX: A Medium‐Resolution 0.8–5.5 Micron Spectrograph and Imager for the NASA Infrared Telescope Facility

ABSTRACT. We present the design, construction, and performance of SpeX, a medium-resolution 0.8–5.5 mm 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 R ∼ 2000 simultaneously across 0.8–2.4, 1.9–4.2, or 2.4–5.5 mm, with a 15 � long slit. A high-throughput low-resolution R ∼ 200 prism mode is also provided for faint-object and occultation spectroscopy. Single-order 60 � long-slit modes with resolving powers up to R ∼ 2000 are available for extended objects. The spectrograph employs an �1 Aladdin 3 1024 # 1024 InSb array and uses narrow slits and a spatial…