CRIRES is a cryogenic high-resolution cross-dispersed infrared echelle spectrograph, developed by ESO. It provides a resolving power of up to 100,000 between 0.95 and 5.38 μm. It was offered for the first time in P79.

The overview for the original (pre-upgrade, pre-August 2014) CRIRES may be found clicking this link

Note that CRIRES was removed in July 2014 for an upgrade. It was not available from P94 onwards. The upgraded CRIRES was reinstalled on the Nasmyth B platform of UT3 in January 2020 but comissioning is still pending. The aim is to offer the instrument for P107 (see the CRIRES plus website here for the latest date). There will also be a science verification, currently planned for  2020.

Publications using data taken by the original (pre August 2014) CRIRES should cite Käufl, H.U. et al. 2004, SPIE, 5492, 1218 with publications using data taken with the upgraded instrument should additionally cite   Dorn, R.J. et al., ESO Messenger, 2014, 156, p7

The upgraded CRIRES is located at the Nasmyth B focus of UT3. Functionally, it can be divided into four units:

  • The fore-optics part provides the field rotation, cold pupil and field stops, adaptive optics and slit viewing.
  • The order sorting filter and cross disperser allow light of only a certain wavelength range to pass through to the echelle.
  • The echelle which is tilt-tuned for wavelength selection, the camera providing a pixel scale of (TBD), and the detectors.
  • The calibration unit outside the cryogenic environment contains light sources for flux/wavelength calibration and detector flat-fielding.

The spectrograph is housed in a vacuum vessel, with the echelle and cross disperser cooled to ~60 Kelvin and the detectors to ~35 Kelvin (TBC). The main characteristics of CRIRES are summarized in Table 1.

Table 1. Main characteristics of CRIRES
Wavelength range
Spectral resolution
50,000 or 100,000
Slit widths
Fixed slits with width 0.0 (closed position), 0.2 and 0.4 arcsec
Slit length
10 arcsec
Adaptive optics feed
60 actuators curvature sensing system
Calibration system
Integrating sphere + cont.+ line lamps + gas-cells + fabry perot + HCL
Slit viewer
H2RG array, J,H,K, 2 neutral density H filters, one ND K filter.
               Slit viewer pixel scale  0.038 arcsec per pixel   (TBC at comissioning)  
Cross-disperser wheel
                                            Six gratings, being Y, J, K, H, L M
Settings needed to cover each band             Y (2), J (2), H (4), K (4), L (7), M (9). Settings are non continuous!  
Echelle grating
40x20cm, 31.6 lines/mm, 63.5 deg. blaze
                        Polarimetry             Line polarisation in YH and JK bands (circular and linear)
Detector array
A 6144x2048 array comprising three Hawaii 2RG detectors
           Science detector pixel scale 0.058 arcsec per pixel (TBC at comissioning)


An example spectrum with the upgraded CRIRES is shown below. Note that the orders are not continuous and to obtain full wavelength coverage more than one setting per band is required (from 2 settings in Y-band to 9 settings in M-band). See the Exposure Time Calculator (ETC) in order to check the wavelength coverage of a particular setting.

Thanks to CRIRES, new phenomena and objects are now available forspectroscopic studies. Table 2 presents a list of science objectives.


Table 2: Science Objectives


Extra-Solar Planets

Radial velocity studies

Direct spectroscopic detection and characterization of CO, CH4.

Solar System

Chemistry, physical conditions, velocity fields, structure

Giant planets, Titan

H3+, CH4, NH3, CH3D, AsH3, H2O,C2H2,C2H6, PH3, CH3, NH3, HCN,C2H2, C2H6, PH3, CH3, NH3, HCN

Terrestrial planets

Mapping of CO depletion in the atmosphere of Mars.


spatial, time mapping of volcanic activity (SO2)


search for tenous CO, CH4 atmosphere


H2O abundance, temperature, velocities,minor species.


Stellar evolution, nucleosynthesis (OB, AGB stars, cluster redgiants, cool MS, C & S stars in galaxy, S/LMC, nearbyglaxies), CNO isotopic abundances unique in IR.

Stellar mass: atomic, molecular lines from secondaries

Stellar winds, mass loss of OB, WR, AGB stars in galaxy andSMC, LMC based on CO,SiO,C2H2, HCN

Atmospheric structure & oscillations in cool stars

Magnetic fields

Star Formation Regions/ISM

Accretion, outflow from embedded YSOs

ISM chemistry, cloud structure using H3+, H2O, CH4, C2H2, NH3



Velocity structure of BLR, NLR, CLR & molecular clouds, Hrecombination, [FeII], [SiIV], H2 lines suffering low dustextinction