Original CRIRES Overview

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.

Table 1. Main characteristics of the original CRIRES
Wavelength range
Resolving power (2 pixels)
50,000 or 100,000
Slit width
fixed slits with width 0.0, 0.2 and 0.4 arcsec since intervention in October 2011, before that 0.05" to 3.0"
Slit length
40 arcsec
Pixel size (spatial direction)
0.086 arcsec
Adaptive optics feed
60 actuators curvature sensing system
Calibration system
Integrating sphere + cont.+ line lamps + gas-cells (N20, CO, soon OCS)
Slit viewer
Aladdin array, J,H,K and 2 neutraldensity H filters, 0.047 arcsec/pix
                                                                      ZnSe Prism
Echelle grating
40x20cm, 31.6 lines/mm, 63.5 deg. blaze
Detector array
4096x512 pixels using 4 Aladdin arrays, with inter-detector gaps of nominally 283 pixels