S. Becerril

CARMENES: Calar Alto high-resolution search for M dwarfs with exo-earths with a near-infrared Echelle spectrograph

CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) is a next-generation instrument to be built for the 3.5m telescope at the Calar Alto Observatory by a consortium of Spanish and German institutions. Conducting a five-year exoplanet survey targeting ~ 300 M stars with the completed instrument is an integral part of the project. The CARMENES instrument consists of two separate spectrographs covering the wavelength range from 0.52 to 1.7 μm at a spectral resolution of R = 85, 000, fed by fibers from the Cassegrain focus of the telescope. The spectrographs are housed in a temperature-stabilized environment in vacuum tanks, to enable a 1m/s radial velocity precision employing a simultaneous ThAr calibration.

EMIR: the GTC NIR multi-object imager-spectrograph

In this contribution we review the overall features of EMIR, the NIR multiobject spectrograph of the GTC. EMIR is at present in the middle of the PD phase and will be one of the first common user instruments for the GTC, the 10 meter telescope under construction by GRANTECAN at the Roque de los Muchachos Observatory (Canary Islands, Spain). EMIR is being built by a Consortium of Spanish, French and British institutes led by the IAC. EMIR is designed to realize one of the central goals of 10m class telescopes, allowing observers to obtain spectra for large numbers of faint sources in an time-efficient manner. EMIR is primarily designed to be operated as a MOS in the K band, but offers a wide range of observing modes, including imaging and spectroscopy, both long slit and multiobject, in the wavelength range 0.9 to 2.5 μm. The present status of development, expected performances and schedule are described and discussed. This project is funded by GRANTECAN and the Plan Nacional de Astronomía y Astrofísica (National Plan for Astronomy and Astrophysics, Spain).

CARMENES. II: optical and opto-mechanical design

CARMENES is a fiber-fed high-resolution échelle spectrograph for the Calar Alto 3.5m telescope. The instrument is built by a German-Spanish consortium under the lead of the Landessternwarte Heidelberg. The search for planets around M dwarfs with a radial velocity accuracy of 1 m/s is the main focus of the planned science. Two channels, one for the visible, another for the near-infrared, will allow observations in the complete wavelength range from 550 to 1700 nm. To ensure the stability, the instrument is working in vacuum in a thermally controlled environment. The optical design of both channels of the instrument and the front-end, as well as the opto-mechanical design, are described.

CARMENES (III): an innovative and challenging cooling system for an ultra-stable NIR spectrograph

The CARMENES project, which is currently at FDR stage, is a last-generation exoplanet hunter instrument to be installed in the Calar Alto Observatory by 2014. It is split into two different spectrographs: one works within the visual range while the other does it in the NIR range. Both channels need to be extremely stable in terms of mechanical and thermal behavior. Nevertheless, due to the operation temperature of the NIR spectrograph, the thermal stability requirement (±0.07 K in 24 hours; ±0.01 K (goal)) becomes actually a major challenge. The solution here proposed consists of a system that actively cools a shield enveloping the optical bench. Thus, the instability produced on the shield temperature is further damped on the optical bench due to the high mass of the latter, as well as the high thermal decoupling between both components, the main heat exchange being produced by radiation. This system -which is being developed with the active collaboration and advice of ESO (Jean-Louis Lizon)- is composed by a previous unit which produces a stable flow of nitrogen gas. The flow so produced goes into the in-vacuum circuitry of the NIR spectrograph and removes the radiative heat load incoming to the radiation shield by means of a group of properly dimensioned heat exchangers. The present paper describes and summarizes the cooling system designed for CARMENES NIR as well as the analyses implemented.

Status of the EMIR mechanical system

EMIR is the NIR multi-object imager and spectrograph for the GTC (Gran Telescopio Canarias). The instrument ADR (Advanced Design Review) was held successfully in March 2006. During the AD phase, a number of mechanical concepts were tested on development prototypes to ensure the feasibility of the PDR proposed designs. This presentation contains an overview of the current mechanical status of the instrument, as well as the prototypes development. It contains the prototype tests results of the collimator first lens barrel, the support trusses, the grisms wheel and the demonstration programme for the cryogenic reconfigurable slit mechanism.

An 8-mm diameter fibre robot positioner for massive spectroscopy surveys

Massive spectroscopic survey are becoming trendy in astrophysics and cosmology, as they can address new fundamental knowledge such as understanding the formation of the Milky Way and probing the nature of the mysterious dark energy. To enable massive spectroscopic surveys, new technology has been developed to place thousands of optical fibres at a given position on a focal plane. This technology needs to be: (1) accurate, with micrometer positional accuracy; (2) fast to minimize overhead; (3) robust to minimize failure; and (4) low cost. In this paper, we present the development, properties, and performance of a new single 8-mm in diameter fibre positioner robot, using two 4-mm DC-brushless gearmotors, that allows us to achieve accuracies up to 0.07 arcsec (5 mu m). This device has been developed in the context of the Dark Energy Spectroscopic Instrument.(1)

CARMENES ultra-stable cooling system: very promising results

CARMENES is a high resolution spectrograph to detect planets through the variation of radial velocity, destined for the Calar Alto Observatory in Almeria, Spain. The optical bench has a working temperature of 140K with a 24 hours stability of ±0,1K; goal ±0,01K. It is enclosed with a radiation shield actively cooled with thermalized nitrogen gas that flows through strategically positioned heat exchangers to remove its radiative load. The cooling system has an external preparation unit (N2GPU), which provides the nitrogen gas through actively vaporizing liquid nitrogen with heating resistances and a three stage circuit flow, each one controlled by an independent PID. Since CARMENES is still in the construction phase, a dedicated test facility has been built in order to simulate the instrument and correctly establish the N2GPU parameters. Furthermore, the test facility allows a wide range of configurations set-ups, which enables a full characterization of the N2GPU and the cooling system. The N2GPU has been designed to offer a wide temperature range of thermally stabilized nitrogen gas flow, which apart from CARMENES could also be used to provide ultra-high thermal stability in other cryogenic instruments. The present paper shows the testing of the cooling performance, the hardware used and the very promising results obtained.

OSIRIS tunable imager and spectrograph for the GTC: from design to commissioning

OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) was the optical Day One instrument for the 10.4m Spanish telescope GTC. It is installed at the Observatorio del Roque de Los Muchachos (La Palma, Spain). This instrument has been operational since March-2009 and covers from 360 to 1000 nm. OSIRIS observing modes include direct imaging with tunable and conventional filters, long slit and low resolution spectroscopy. OSIRIS wide field of view and high efficiency provide a powerful tool for the scientific exploitation of GTC. OSIRIS was developed by a Consortium formed by the Instituto de Astrofísica de Canarias (IAC) and the Instituto de Astronomía de la Universidad Nacional Autónoma de México (IA-UNAM). The latter was in charge of the optical design, the manufacture of the camera and collaboration in the assembly, integration and verification process. The IAC was responsible for the remaining design of the instrument and it was the project leader. The present paper considers the development of the instrument from its design to its present situation in which is in used by the scientific community.

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.

eXtreme multiplex spectrograph: a high-demanding mechanical design

XMS is a multi-channel wide-field spectrograph designed for the prime focus of the 3.5m Calar-Alto telescope. The instrument is composed by four quadrants, each of which contains a spectrograph channel. An innovative mechanical design -at concept/preliminary stage- has been implemented to: 1) Minimize the separation between the channels to achieve maximal filling factor; 2) Cope with the very constraining space and mass overall requirements; 3) Achieve very tight alignment tolerances; 4) Provide lens self-centering under large temperature excursions; 5) Provide masks including 4000 slits (edges thinner than 100μ). An overview of this very challenging mechanical design is here presented.