Overview

CRIRES is a cryogenic high-resolution pre-dispersed infrared echelle spectrograph, developed by ESO. It provides a resolving power of up to 100,000 between 0.95 and 5.2μm. It was offered for the first time in P79.

CRIRES is located at the Nasmyth A focus of UT1. 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 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 is housed in a vacuum vessel, with its optics cooled to ~65K and the detectors to ~25K. The main characteristics of CRIRES are summarized in Table 1.

Table 1. Main characteristics of CRIRES

Wavelength range
0.95-5.2μm
Resolving power (2 pixels)
100,000
Slit width
0.05 - 3.0 arcsec (recommended values: 0.2 - 0.4)
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 neutral density H filters, 0.047 arcsec/pix
Pre-disperser
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

Thanks to CRIRES, new phenomena and objects are now available for spectroscopic studies. Table 2 presents a list of science objectives.
Table 2: Science Objectives

Extra-Solar Planets

Radial velocities 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

CO, HCL, HF, HDO, H2O, OCS
Mapping of CO depletion in the atmosphere of Mars.

Io

spatial, time mapping of volcanic activity (SO2)

Pluto/Charon/Triton

search for tenous CO, CH4 atmosphere

Comets

H2O abundance, temperature, velocities, minor species.

Stars

Stellar evolution, nucleosynthesis (OB, AGB stars, cluster red giants, cool MS, C & S stars in galaxy, S/LMC, nearby glaxies), 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 Formation Regions/ISM

Accretion, outflow from embedded YSOs

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

Extragalactic

AGN

Velocity structure of BLR, NLR, CLR & molecular clouds, H recombination, [FeII], [SiIV], H2 lines suffering low dust extinction