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 ≈ 0.004 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 2.7 m and the NASA Infrared Telescope Facility 3 m telescopes and has proved to be both sensitive and versatile.