CARMENES. V: Non-cryogenic solutions for YJH-band NIR instruments

Currently, every single instrument using NIR detectors is cooled down to cryogenic temperatures to minimize the thermal flux emitted by a warm instrument. Cryogenization, meaning reaching very low operating temperatures, is a must when the K band is needed for the science case. This results in more complex and more expensive instruments. However, science cases that do not benefit from observing in the K band, like the detection of exoplanets around M dwarfs through the radial velocity technique, can make use of non-cryogenic instruments. The CARMENES instrument is implementing a cooling system which could allow such a solution. It is being built by a consortium of eleven Spanish and German institutions and will conduct an exoplanet survey around M dwarfs. Its concept includes two spectrographs, one equipped with a CCD for the range 550-950 nm, and one with HgCdTe detectors for the range from 950-1700 nm, covering therefore the YJH bands In this contribution, different possibilities are studied to reach the final cooling solution to be used in CARMENES, all of them demonstrated to be feasible, within the requirements of the SNR requested by the science case.