The original CRIRES was a cryogenic high-resolution pre-dispersed infrared echelle spectrograph, developed by ESO. It provided a resolving power of up to 100,000 between 0.95 and 5.38 μm. It was offered from P79 through P93.

This page refers to the original (pre-August 2014) CRIRES. For the upgraded CRIRES (the CRIRES+ project) please use the following link

The original CRIRES was located at the Nasmyth B focus of UT1. Functionally, it was divided into four units:

• The fore-optics part provides the field rotation, cold pupil and field stops, adaptive optics and slit viewing.
• The prism pre-disperser isolates one echelle order and minimizes the total amount of light entering into the high-resolution section.
• The high-resolution section comprises the collimator, the echelle which is tilt-tuned for wavelength selection, the camera providing the 0."086/pixel scale, and the detectors.
• The calibration unit outside the cryogenic environment contains light sources for flux/wavelength calibration and detector flat-fielding.

The spectrograph was housed in a vacuum vessel, with its optics cooled to ~65K and the detectors to ~25K. The main characteristics of the original CRIRES are summarized in Table 1.