The Large Millimeter Telescope (LMT) Alfonso Serrano is a bi-national (Mexico and USA) telescope facility operated by the Instituto Nacional de Astrofisica, Optica y Electronica (INAOE) and the University of Massachusetts. The LMT is designed as a 50-m diameter single-dish millimeter-wavelength telescope that is optimized to conduct scientific observations at frequencies between ~70 and 350 GHz. The LMT is constructed on the summit of Sierra Negra at an altitude of 4600m in the Mexican state of Puebla. The site offers excellent mm-wavelength atmospheric transparency all-year round, and the opportunity to conduct submillimeter wavelength observations during the winter months. Following first-light observations in mid-2011, the LMT began regular scientific operations in 2014 with a shared-risk Early Science observing program using the inner 32-m diameter of the primary reflector with an active surface control system. The LMT has already performed successful VLBI observations at 3mm with the High Sensitivity Array and also at 1.3mm as part of the Event Horizon Telescope. Since early 2018 the LMT has begun full scientific operations as a 50-m diameter telescope, making the LMT 50-m the world´s largest single-dish telescope operating at 1.1mm. I will describe the current status of the telescope project, including the early scientific results from the LMT 50-m, as well the instrumentation development program, the plan to improve the overall performance of the telescope, and the on-going transition towards the formation of the LMT Observatory to support the scientific community in their use of the LMT to study the formation and evolution of structure at all cosmic epochs.
The mm-wavelength sky reveals the initial phase of structure formation, at all spatial scales, over the entire observable history of the Universe. Over the past 20 years, advances in mm-wavelength detectors and camera systems have allowed the field to take enormous strides forward – particularly in the study of the Cosmic Microwave Background – but limitations in mapping speeds, sensitivity and resolution have plagued studies of astrophysical phenomena. In fact, limitations due to inherent biases in the ground-based mm-wavelength surveys conducted over the last 2 decades continue to motivate the need for deeper and wider-area maps made with increased angular resolution. TolTEC is a new camera that will fill the focal plane of the 50m diameter Large Millimeter Telescope (LMT) and provide simultaneous, polarization-sensitive imaging at 2.0, 1.4, and 1.1mm wavelengths. The instrument, now under construction, is a cryogenically cooled receiver housing three separate kilo-pixel arrays of Kinetic Inductance Detectors (KIDs) that are coupled to the telescope through a series of silicon lenses and dichroic splitters. TolTEC will be installed and commissioned on the LMT in early 2019 where it will become both a facility instrument and also perform a series of 100 hour “Legacy Surveys” whose data will be publicly available. The initial four surveys in this series: the Clouds to Cores Legacy Survey, the Fields in Filaments Legacy Survey, the Ultra-Deep Legacy Survey and the Large Scale Structure Survey are currently being defined in public working groups of astronomers coordinated by TolTEC Science Team members. Data collection for these surveys will begin in late 2019 with data releases planned for late 2020 and 2021. Herein we describe the instrument concept, provide performance data for key subsystems, and provide an overview of the science, schedule and plans for the initial four Legacy Survey concepts.
MEGARA is the new generation IFU and MOS optical spectrograph built for the 10.4m Gran Telescopio CANARIAS (GTC). The project was developed by a consortium led by UCM (Spain) that also includes INAOE (Mexico), IAA-CSIC (Spain) and UPM (Spain). The instrument arrived to GTC on March 28th 2017 and was successfully integrated and commissioned at the telescope from May to August 2017. During the on-sky commissioning we demonstrated that MEGARA is a powerful and robust instrument that provides on-sky intermediate-to-high spectral resolutions RFWHM ~ 6,000, 12,000 and 20,000 at an unprecedented efficiency for these resolving powers in both its IFU and MOS modes. The IFU covers 12.5 x 11.3 arcsec2 while the MOS mode allows observing up to 92 objects in a region of 3.5 x 3.5 arcmin2. In this paper we describe the instrument main subsystems, including the Folded-Cassegrain unit, the fiber link, the spectrograph, the cryostat, the detector and the control subsystems, and its performance numbers obtained during commissioning where the fulfillment of the instrument requirements is demonstrated.
On June 25th 2017, the new intermediate-resolution optical IFU and MOS of the 10.4-m GTC had its first light. As part of the tests carried out to verify the performance of the instrument in its two modes (IFU and MOS) and 18 spectral setups (identical number of VPHs with resolutions R=6000-20000 from 0.36 to 1 micron) a number of astronomical objects were observed. These observations show that MEGARA@GTC is called to fill a niche of high-throughput, intermediateresolution IFU and MOS observations of extremely-faint narrow-lined objects. Lyman-α absorbers, star-forming dwarfs or even weak absorptions in stellar spectra in our Galaxy or in the Local Group can now be explored to a new level. Thus, the versatility of MEGARA in terms of observing modes and spectral resolution and coverage will allow GTC to go beyond current observational limits in either depth or precision for all these objects. The results to be presented in this talk clearly demonstrate the potential of MEGARA in this regard.
MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is an optical Integral-Field Unit and Multi-Object Spectrograph designed for the GTC (Gran Telescopio de Canarias) 10.4m telescope in La Palma, it is expected that the spectrograph will be delivered to GTC towards the end of 2016. MEGARA includes an open cycle cryostat which harbors the scientific CCD of the instrument at an operating temperature of 153 K, this cryogenic system has been designed and integrated by the “Astronomical Instrumentation Lab for Millimeter Wavelengths” at the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) in Mexico. Early this year the cryostat has finished its fabrication and now it is on AIV phases, in this paper we report the cryostat CCD-head and dewar back integration, vacuum and cryogenic test results are also reported. The final integration of the cryostat with the other components of the instrument is taking place at LICA lab at the Universidad Complutense de Madrid.
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 (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is an optical Integral-Field Unit and
Multi-Object Spectrograph designed for the GTC (Gran Telescopio de Canarias) 10.4m telescope in La Palma.
MEGARA project has already passed preliminary design review and the optics critical design review, first-light it is
expected to take place at the end of 2016. MEGARA is a development under a GRANTECAN contract.
In this paper we summarize the current status of the LN2 open-cycle cryostat which has been designed by the
“Astronomical Instrumentation Lab for Millimeter Wavelengths” at the Instituto Nacional de Astrofísica, Óptica y
Electrónica (INAOE) and emphasize the key parts of the system that have updated since the Preliminary Design, the
main activities related to acceptance, integration, fabrication and maintenance plans which fit into the overall structure of
the management plan of MEGARA are also described. The cryogenic work package of MEGARA has completed all the
design stages and is ready for its Critical Design Review and then proceed to fabrication.
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.
MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is the new integral field unit (IFU) and
multi-object spectrograph (MOS) instrument for the GTC. The spectrograph subsystems include the pseudo-slit, the
shutter, the collimator with a focusing mechanism, pupil elements on a volume phase holographic grating (VPH) wheel
and the camera joined to the cryostat through the last lens, with a CCD detector inside.
In this paper we describe the full preliminary design of the cryostat which will harbor the CCD detector for the
spectrograph. The selected cryogenic device is an LN2 open-cycle cryostat which has been designed by the
"Astronomical Instrumentation Lab for Millimeter Wavelengths" at INAOE. A complete description of the cryostat
main body and CCD head is presented as well as all the vacuum and temperature sub-systems to operate it. The CCD is
surrounded by a radiation shield to improve its performance and is placed in a custom made mechanical mounting which
will allow physical adjustments for alignment with the spectrograph camera. The 4k x 4k pixel CCD231 is our selection
for the cryogenically cooled detector of MEGARA. The characteristics of this CCD, the internal cryostat cabling and
CCD controller hardware are discussed. Finally, static structural finite element modeling and thermal analysis results are
shown to validate the cryostat model.
We report the design of a sub-millimeter Fourier Transform Spectrometer of the Martin Puplett type (FTS-MP
here after). The instrument will be installed on Sierra La Negra, and will operate from ~215 GHz to 1 THz
approximately with a moderate resolution of 500 MHz. The main motivations of the work are the development of
basic instrumentation for characterizing the LMT site (Large Millimeter Telescope) as well as optical components
and to provide a portable broadband system for site testing. The collected data will be used for transmission
model validation. The data also will influence the design of the new generation of sub-millimeter and millimeter
cameras for the LMT. In the present work we emphasize cryogenic detector system design (bolometer detector
and coupling optics) and the optical system layout for the FTS-MP. Test measurements in the laboratory are
reported in this work.