This page describes the upgraded CRIRES, currently installed at UT3. An overview for the original (pre-upgrade, pre-August 2014) CRIRES can be found clicking this link.

The VLT CRyogenic high-resolution InfraRed cross dispersed Echelle Spectrograph (CRIRES) provides a resolving power of at least 43,000 (0.4" slit) or 86,000 (0.2" slit) in the spectral range from 0.95 to 5.3μm. As part of the upgrade, linear and circular polarisation capabilities have been added in the YJ and HK bands. CRIRES offers relatively high spatial (extended sources), spectral and temporal resolution. Spectral coverage is maximized through the use of a cross disperser and a mosaic of three Hawaii H2RG arrays providing an effective 6144 x 2048 pixel focal plane detector. Adaptive Optics (MACAO - Multi-Applications Curvature Adaptive optics) is used to feed the light into the slit and thereby enhance the signal-to-noise ratio of the observations. The main characteristics of the instrument modes are summarized below (for more details on the instrument performance, see the Instrument Description).


Wavelength range
0.95 - 5.3 μm
Minimum spectral resolving power
43,000 (0.4" slit) or 86,000 (0.2" slit) in the wavelength settings L3144, L3262, M4187, M4211 and M4266;
46,000 (0.4" slit) or 92,000 (0.2" slit) for all other wavelength settings
Slit widths
Fixed slits with 0.2 and 0.4 arcsec width
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 with J, H, K, 2 neutral density H filters, one ND K filters.
Slit viewer pixel scale 0.0373 arcsec per pixel
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! Click here to see a plot summarizing the 29 wavelength settings.
Echelle grating
40 x 20 cm, 31.6 lines/mm, 63.5 deg. blaze
Polarimetry Line polarisation in YH and JK bands (circular and linear)
Detector array
6144x2048 px array comprising three Hawaii 2RG detectors
Science detector pixel scale 0.056 arcsec per pixel


Science Objectives


  • Radial velocity studies to detect and follow-up exoplanets (especially those who linger around M-dwarfs).
  • Direct spectroscopic detection and characterization of exoplanet atmospheres

Solar System

  • Chemistry, physical conditions, velocity fields, structure
  • Molecular species in giant planets and Titan
  • Terrestrial planet atmospheres; Mapping of CO depletion in the atmosphere of Mars
  • Mapping of volcanic activity (SO2) in Io
  • Search for tenous CO, CH4 atmosphere in Pluto / Charon / Triton
  • Abundances, temperatures, velocities of comets


  • 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 and SMC, LMC based on CO,SiO,C2H2, HCN
  • Atmospheric structure & oscillations in cool stars
  • Magnetic fields

Star forming regions / ISM

  • Accretion, outflow from embedded young stellar objects (YSOs)
  • ISM chemistry, cloud structure using H3+, H2O, CH4, C2H2, NH3


  • Active galactic nuclei (AGNs): Velocity structure of BLR, NLR, CLR & molecular clouds, Hrecombination, [FeII], [SiIV], H2 lines suffering low dustextinction