TEXES: A Sensitive High‐Resolution Grating Spectrograph for the Mid‐Infrared

We discuss the design and performance of TEXES, the Texas Echelon Cross Echelle Spectrograph. TEXES is a mid-infrared (5-25 µm) spectrograph with several operating modes: high-resolution, cross-dispersed with a resolving power of R = λ/δλ ≈ 100,000, 0.5 % spectral coverage, and a ∼ 1.5 × 8 ′ ′ slit; medium-resolution long-slit, with R ≈ 15,000, 0.5 % coverage, and a ∼ 1.5×45 ′ ′ slit; low-resolution long-slit, with δλ ≈.004 µm, 0.25 µm coverage, and a ∼ 1.5 × 45 ′ ′ slit; and source acquisition imaging with 0.33 ′′ pixels and a 25 × 25 ′ ′ field of view on a 3 m telescope. TEXES has been used at the McDonald Observatory 2.7m and the IRTF 3m telescopes, and has proven to be both sensitive and versatile. Subject headings: infrared: general — instrumentation: spectrographs — techniques: spectroscopic 1.