TEXES, the Texas Echelon Cross Echelle Spectrograph, is a versatile mid-infrared (5-25 μm) spectrograph that can be used in several operating modes: high resolution cross-dispersed, with a resolving power of R = 50-100,000; medium resolution long-slit, with R~15,000; low resolution long-slit, with R~3000; source acquisition imaging; and pupil imaging.
The design of TEXES is unique in several respects. The primary disperser is a variation on an echelon, a steeply and coarsely blazed (R10 with 0.3 inch groove spacing), 36 inch long, diamond-machined aluminum grating. The cross disperser is an R4 echelle used in low order at R2, with the grooves acting as corner reflectors. Cold mechanisms allow the echelon to be bypassed to use the cross disperser in long-slit mode. A first-order grating can be inserted in front of the echelle for lower resolution. In addition, the low resolution grating can be turned face-on to act as a mirror allowing source-acquisition imaging and pupil viewing.
TEXES has been used for 8 nights on the McDonald Observatory 2.7m and 45 nights on the NASA IRTF 3m telescopes over the last 2 1/2 years. Sources observed include planets and planetary satellites, stellar atmospheres, circumstellar outflows and disks, and molecular clouds and HII regions in the Milky Way and external galaxies.