E. Sánchez-Blanco

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.

MEGARA: the future optical IFU and multi-object spectrograph for the 10.4m GTC telescope

In these proceedings we give a summary of the characteristics and current status of the MEGARA instrument, the future optical IFU and MOS for the 10.4-m Gran Telescopio Canarias (GTC). MEGARA is being built by a Consortium of public research institutions led by the Universidad Complutense de Madrid (UCM, Spain) that also includes INAOE (Mexico), IAA-CSIC (Spain) and UPM (Spain). The MEGARA IFU includes two different fiber bundles, one called LCB (Large Compact Bundle) with a field-of-view of 12.5×11.3 arcsec2 and a spaxel size of 0.62 arcsec yielding spectral resolutions between R=6,800-17,000 and another one called SCB (Small Compact Bundle) covering 8.5×6.7 arcsec2 with hexagonally-shaped and packed 0.42-arcsec spaxels and resolutions R=8,000-20,000. The MOS component allows observing up to 100 targets in 3.5×3.5 arcmin2. Both the IFU bundles and the set of 100 robotic positioners of the MOS will be placed at one of the GTC Folded-Cass foci while the spectrographs (one in the case of the MEGARA-Basic concept) will be placed at the Nasmyth platform. On March 2012 MEGARA passed the Preliminary Design Review and its first light is expected to take place at the end of 2015.

MEGARA: a new generation optical spectrograph for GTC

MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is an optical Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) designed for the GTC 10.4m telescope in La Palma. MEGARA offers two IFU fiber bundles, one covering 12.5x11.3 arcsec2 with a spaxel size of 0.62 arcsec (Large Compact Bundle; LCB) and another one covering 8.5x6.7 arcsec2 with a spaxel size of 0.42 arcsec (Small Compact Bundle; SCB). The MEGARA MOS mode will allow observing up to 100 objects in a region of 3.5x3.5 arcmin2 around the two IFU bundles. Both the LCB IFU and MOS capabilities of MEGARA will provide intermediate-to-high spectral resolutions (RFWHM~6,000, 12,000 and 18,700, respectively for the low-, mid- and high-resolution Volume Phase Holographic gratings) in the range 3650-9700ÅÅ. These values become RFWHM~7,000, 13,500, and 21,500 when the SCB is used. A mechanism placed at the pseudo-slit position allows exchanging the three observing modes and also acts as focusing mechanism. The spectrograph is a collimator-camera system that has a total of 11 VPHs simultaneously available (out of the 18 VPHs designed and being built) that are placed in the pupil by means of a wheel and an insertion mechanism. The custom-made cryostat hosts an E2V231-84 4kx4k CCD. The UCM (Spain) leads the MEGARA Consortium that also includes INAOE (Mexico), IAA-CSIC (Spain), and UPM (Spain). MEGARA is being developed under a contract between GRANTECAN and UCM. The detailed design, construction and AIV phases are now funded and the instrument should be delivered to GTC before the end of 2016.

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.

MEGARA, the new intermediate-resolution optical IFU and MOS for GTC: getting ready for the telescope

MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is an optical Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) designed for the GTC 10.4m telescope in La Palma that is being built by a Consortium led by UCM (Spain) that also includes INAOE (Mexico), IAA-CSIC (Spain), and UPM (Spain). The instrument is currently finishing AIV and will be sent to GTC on November 2016 for its on-sky commissioning on April 2017. The MEGARA IFU fiber bundle (LCB) covers 12.5x11.3 arcsec2 with a spaxel size of 0.62 arcsec while the MEGARA MOS mode allows observing up to 92 objects in a region of 3.5x3.5 arcmin2 around the IFU. The IFU and MOS modes of MEGARA will provide identical intermediate-to-high spectral resolutions (RFWHM~6,000, 12,000 and 18,700, respectively for the low-, mid- and high-resolution Volume Phase Holographic gratings) in the range 3700-9800ÅÅ. An x-y mechanism placed at the pseudo-slit position allows (1) exchanging between the two observing modes and (2) focusing the spectrograph for each VPH setup. The spectrograph is a collimator-camera system that has a total of 11 VPHs simultaneously available (out of the 18 VPHs designed and being built) that are placed in the pupil by means of a wheel and an insertion mechanism. The custom-made cryostat hosts a 4kx4k 15-μm CCD. The unique characteristics of MEGARA in terms of throughput and versatility and the unsurpassed collecting are of GTC make of this instrument the most efficient tool to date to analyze astrophysical objects at intermediate spectral resolutions. In these proceedings we present a summary of the instrument characteristics and the results from the AIV phase. All subsystems have been successfully integrated and the system-level AIV phase is progressing as expected.

MEGARA spectrograph optics

MEGARA is the next optical Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) for Gran Telescopio Canarias. The instrument offers two IFUs plus a Multi-Object Spectroscopy (MOS) mode: a large compact bundle covering 12.5 arcsec x 11.3 arcsec on sky with 100 μm fiber-core; a small compact bundle, of 8.5 arcsec x 6.7 arcsec with 70 μm fiber-core and a fiber MOS positioner that allows to place up to 100 mini-bundles, 7 fibers each, with 100 μm fiber-core, within a 3.5 arcmin x 3.5 arcmin field of view, around the two IFUs. The fibers, organized in bundles, end in the pseudo-slit plate, which will be placed at the entrance focal plane of the MEGARA spectrograph. The large IFU and MOS modes will provide intermediate to high spectral resolutions, R=6800-17000. The small IFU mode will provide R=8000-20000. All these resolutions are possible thanks to a spectrograph design based in the used of volume phase holographic gratings in combination with prisms to keep fixed the collimator and camera angle. The MEGARA optics is composed by a total of 53 large optical elements per spectrograph: the field lens, the collimator and the camera lenses plus the complete set of pupil elements including holograms, windows and prisms. INAOE, a partner of the GTC and a partner of MEGARA consortium, is responsible of the optics manufacturing and tests. INAOE will carry out this project working in an alliance with CIO. This paper summarizes the status of MEGARA spectrograph optics at the Preliminary Design Review, held on March 2012.

MEGARA focal plane subsystems

MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is the future optical Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) for GTC. The Fiber Units are placed at one Folded Cassegrain focus and feed the spectrograph located on a Nasmyth-type platform. This paper summarizes the status of the design of the MEGARA Folded Cassegrain Subsystems after the PDR (held on March 2012), as well as the prototyping that has been carried out during this phase. The MEGARA Fiber Unit has two IFUs: a Large Compact Bundle covering 12.5 arcsec x 11.3 arcsec on sky (100 microns fiber-core), and a Small Compact Bundle, of 8.5 arcsec x 6.7 arcsec (70 microns fiber-core), plus a Fiber MOS positioner, able to place up to 100 mini-bundles 7 fibers each (100 microns fiber-core) in MOS configuration within a 3.5arcmin x 3.5arcmin FOV. A field lens provides a telecentric focal plane where the fibers are located. Microlens arrays couple the telescope beam to the collimator focal ratio at the entrance of the fibers (providing the f/17 to f/3 focal ratio reduction to enter into the fibers). Finally, the fibers, organized in bundles, end in the pseudo-slit plate, which will be placed at the entrance focal plane of the MEGARA spectrographs.

Optical design for MEGARA: a multi-object spectrograph for the GTC

MEGARA is a multi-object spectrograph project for the 10.4m Gran Telescopio Canarias with medium to high resolution: R ~ 5600 - 17000. The instrument operates in three modes that cover different sky areas and that can run simultaneously: (1) the compact mode through a large central Integral Field Unit with minimum fiber pitch, covering a field of view on sky of 12 arcsec × 14 arcsec, (2) the sparse mode with fibers covering 1 arcmin × 1arcmin in three pointings and (3) the dispersed mode with a grid of nearly 100 robotics positioners able to place 7-fiber minibundles over a large field of view of 3.5 arcmin × 3.5 arcmin. The spectrograph is composed by a pseudo-slit, where the fibers are placed simulating a long slit; a slit shutter is placed just behind the pseudo-slit, a collimator, a 162mm pupil where the volume phase holographic gratings are placed, and the camera with the detector. Here we describe the spectrograph optical rationale, the conceptual optical design and the expected system performance.

MEGARA fiber bundles

MEGARA (Multi Espectrógrafo en GTC de Alta Resolución para Astronomía) is the future optical Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) for the 10.4-m Gran Telescopio CANARIAS (GTC). MEGARA has three different fiber bundles, the Large Central Bundle covering 12.5 arcsec x 11.3 arcsec on sky, the Small Compact Bundle, of 8.5 arcsec x 6.7 arcsec, and a Fiber MOS positioner system that is able to place up to 100 mini-bundles with 7 fibers each in MOS configuration within a 3.5 arcmin x 3.5 arcmin FOV. The MEGARA focal plane subsystems are located at one of the GTC Folded Cassegrain focal stations. A field lens provides a telecentric focal plane, where the fibers are located. Micro-lenses arrays couple the telescope beam to the collimator focal ratio at the entrance of the fibers. Finally, the fibers, organized in bundles conducted the light from the focal plane to the pseudo-slit plates at the entrance of the MEGARA spectrograph, which shall be located at one of the Nasmyth platforms. This article also summarizes the prototypes already done and describes the set-up that shall be used to integrate fibers and micro-lens and characterize the fiber bundles.

VIENTOS: a feasibility study of innovative pupil systems for the new generation of instruments in the large telescopes

The goal of VIENTOS project is to analyze pupil innovative systems that could be used in the new generation of instruments for the large telescopes. This study tries to identify the current scientific needs, to understand why some of them have not been fulfilled yet (due to pre-conceived technical ideas or to managerial reasons) and to propose optomechanical solutions for these pupil elements that could produce a qualitative leap in the performance of the instruments to operate in the large telescopes. VIENTOS is currently on-going as a collaborative project between FRACTAL and the University Complutense of Madrid (UCM) and is being partially funded by a CDTI grant under the program Industry for Science. CDTI is the Development and Industrial Transfer Center from the Minister of Science and Innovation (Spain). Among the different innovative systems that we have carried out, our team has explored potential solutions for narrow band Imaging with tunable filters in the near-IR and a novel pupil system called sliced-pupil grating, a device designed for increasing the spectral resolution in astronomical spectrographs, without changing the geometry of the main optics. Nanotechnology customized filters to be applicable to astronomical systems are under study.