Final Design of the CARMENES M-Dwarf Radial-Velocity Survey Instrument
Abstract
CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) is a next-generation instrument being built for the 3.5m telescope at the Calar Alto Observatory by a consortium of eleven Spanish and German institutions. CARMENES will conduct a five-year exoplanet survey targeting ~300 M dwarfs. The CARMENES instrument consists of two separate échelle spectrographs covering the wavelength range from 0.55 to 1.7 μm at a spectral resolution of R = 82,000, fed by fibers from the Cassegrain focus of the telescope. For late-M spectral types, the wavelength range around 1.0 μm (Y band) is the most important wavelength region for radial velocity work. Therefore, the efficiency of CARMENES will be optimized in this range. Since CCDs do not provide high enough efficiency around 1.0 μm and no signal at all beyond the Si cutoff at 1.1 μm, a near-IR detector is required. It is thus natural to adopt an instrument concept with two spectrographs, one equipped with a CCD for the range 0.55-1.05 μm, and one with HgCdTe detectors for the range from 0.9-1.7 μm. Each spectrograph will be coupled to the 3.5m telescope with its own optical fiber. The front end will contain a dichroic beam splitter and an atmospheric dispersion corrector, to feed the light into the fibers leading to the spectrographs. Guiding is performed with a separate camera. Additional fibers are available for simultaneous injection of light from emission line lamps for RV calibration. The spectrographs are mounted on benches inside vacuum tanks located in the coudé laboratory of the 3.5m dome. Each vacuum tank is equipped with a temperature stabilization system capable of keeping the temperature constant to within ±0.01K over 24h. The visible-light spectrograph will be operated near room temperature, the NIR spectrograph will be cooled to 140K. The CARMENES instrument passed its preliminary design review in July 2011; the final design is just being completed. Commissioning of the instrument is planned for the first half of 2014. At least 600 useable nights have been allocated at the Calar Alto 3.5m Telescope for the CARMENES survey in the time frame from 2014 to 2018.
- Publication:
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American Astronomical Society Meeting Abstracts #221
- Pub Date:
- January 2013
- Bibcode:
- 2013AAS...22114905Q