Instrument Description

This webpage refers to the upgraded CRIRES (the CRIRES+ project).

Original CRIRES

The instrument description for the original (pre August 2014) CRIRES may be found in the following link. The current pages are in development and will describe the capabilities of the upgraded CRIRES  (the CRIRES+ project). Numbers for many of the pameters are unknown and will be updated after comissioning.

The upgraded CRIRES (CRIRES+ project)

The upgraded CRIRES improves on the original CRIRES by means of a bigger detector array, a cross disperser, linear and circular polarimitry (spectral lines only) and new calibration sources.

Sensitivities

Sensitivities derived from commissioning data will be listed in Table 1. The values are valid for point sources. They were determined using a 0.4 arcsec slit, adaptive optics under an optical seeing of 0.8 arcsec. They correspond to a S/N of 10 for a 1h on-source integration in one spectral dispersion element. They were obtained by integrating the profile along the spatial direction.

Table 1. Sensitivities
Band
mJy
Magnitude
Y (948-1120 nm)
   
J (1116-1362 nm)
 
 
H (1423-1769 nm)
 
 
K (1972-2624 nm)
 
 
L (2869-4188 nm)
   
M (3583-5200* nm)
(* detector cutoff)
   

Science detector characteristics

Typical values for the main characteristics of the science detectors are listed in Table 3.

Table 3. Typical detector characteristics
Read-out noise in e- (rms)
Det1, Det2, Det3
11, 12, 12  
Dark current  (e- per second). All Detectors
                     < 0.003  
Gain (e- /  ADU)
Det1, Det2, Det3
              2.29, 2.18, 2.00
Saturation level (e-)
Det1, Det2, Det3
60,000
61,000
66,000
Non linearity (pc)  Approximately 5 percent in the range 5,000 to 20,000 ADU

Adaptive Optics

The MACAO used for CRIRES is equipped with a wavefront sensor sensitive in the R band. The flux on the Avalanche Photo Diodes islimited to 1 million counts in order not to damage the devices. Stars fainter than R ~ 11 mag can be dimmed by a up ~ 9 mag thanksto a set of neutral density filters. Hence, stars brighter than R ~ ? mag cannot be used as AO guide stars. Stars fainter thanR ~ ? mag will not result in any improvement. Good correction under average seeing is still obtained with stars as faint as R ~ 14 mag. Any star fainter than this will require good to excellent atmospheric conditions to provide any image quality improvement.

The field selector allows the selection of the AO star within a 30 arcsec field centered on the nominal position of the science target. However, if the AO star lies at more than 10 arcsecs from the science target, the image quality is significantly improved only under good atmospheric conditions. Under excellent conditions, R < 11 mag stars as far as 20 - 30 arcsec can still lead to a modest improvement of the image quality.