The Mexico-UK Submillimeter Camera for AsTronomy (MUSCAT) is a continuum camera in the 1.1-mm band for the Large Millimeter Telescope (LMT), with 1458 lumped-element kinetic inductance detectors distributed across six arrays. Installed on the telescope at the end of 2021, we present the characterization of the detector beams of four of the six arrays based on the beam map observations of bright point sources developed during the first commissioning campaign between February and June 2022. With all the observations, we estimate the average positions of each detector with an average error in azimuth of less than 0.70 arcsec and less than 1.05 arcsec in elevation. From the positions, we created the coadded maps of all the detectors, from which we selected only eight observations to calculate the mean beam width of MUSCAT-LMT, of 6.32±0.36 arcsec×5.78±0.19 arcsec. By stacking the maps, we identify the sidelobes with three main structures whose amplitudes are ∼3% with respect to the main beam.
Sub-mm and mm wavelengths provide a unique view of the Universe, from the gas and dust that fills and surrounds galaxies to the chromosphere of our own Sun. Current single-dish facilities have presented a tantalising view of the brightest (sub-)mm sources, and interferometers have provided the exquisite resolution necessary to analyse the details in small fields, but there are still many open questions that cannot be answered with current facilities: Where are all the baryons? How do structures interact with their environments? What does the time-varying (sub-)mm sky look like? In order to make major advances on these questions and others, what is needed now is a facility capable of rapidly mapping the sky spatially, spectrally, and temporally, which can only be done by a high throughput, single-dish observatory. An extensive design study for this new facility is currently being undertaken. In this paper, we focus on the key science drivers and the requirements they place on the observatory. As a 50m single dish telescope with a 1–2° field of view, the strength of the Atacama Large Aperture Submillimeter Telescope (AtLAST) is in science where a large field of view, highly multiplexed instrumentation and sensitivity to faint large-scale structure is important. AtLAST aims to be a sustainable, upgradeable, multipurpose facility that will deliver orders of magnitude increases in sensitivity and mapping speeds over current and planned telescopes.
MUSCAT is a new 1.1 mm band receiver which was installed on the 50 m Large Millimeter Telescope atop Volc´an Sierra Negra in Puebla, Mexico during the final quarter of 2021 and commissioned on sky throughout 2022. MUSCAT uses a novel cooling chain consisting of a commercial pulse tube cooler, two thermal stages of passively-switched continuous sorption coolers, and a final miniature dilution refrigerator. Through this system MUSCAT achieves a continuous temperature of 120 mK at the focal plane and has shown continuous operation at this temperature for greater than 100 days during readiness testing. Through minimising the amount of helium-3 required, the design on MUSCAT’s cryogenic systems produced a reliable, cost-effective cooling platform. Here we present the cryogenic design and performance of MUSCAT on-sky and compare this to that achieved during deployment-readiness testing at Cardiff (UK). We consider both cooldown time and achieved base temperature. We look at the impact on operation of relocating a pulse-tube cooled instrument from a development lab running on a 50 Hz mains electricity supply to a site running at 60 Hz. Finally, we describe the process of preparing the MUSCAT instrument for shipping and assess the success of this process in terms of remedial work required upon arrival.
The MUSCAT camera is a second-generation continuum camera at the 50-m Large Millimetre Telescope (LMT) operating in the 1.1 mm band, installed in late 2021 and commissioned in early 2022. The instrument’s focal plane has 1458 horn-coupled lumped-element kinetic inductance detectors (LEKIDs) divided into six arrays deposited on three silicon wafers. This work presents the preliminary on-sky performance results of the focal plane obtained during the commissioning campaign. We characterise the detector’s beam size and shape, mapping the point-like source 3C 279 along the focal plane using raster scans, known as beam mapping. It also allows us to identify which resonance frequencies correspond to each detector located in the focal plane, which leads us to a more complete understanding of the behaviour of the detectors, providing us with a reasonable estimation of the array yield. Finally, we compare these results with those obtained during the characterization of the focal plane in the Cardiff laboratory, previously reported in Tapia et al. 2020.
The MUSCAT is a binational collaboration, led by the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) and Cardiff University, dedicated to transfer a variety of skills and experience in the development of technologies for the next generation of sub-mm instrumentation. This primary objective includes the capability to design and fabricate LEKID arrays, design and construct optical, mechanical and cryogenic refrigeration systems operating at temperatures below 150 mK, together with the integration and programming of the readout electronics for multiple detector sub-arrays. The successful development and testing of MUSCAT has provided the Large Millimeter Telescope (LMT) with a large-format millimeter-wavelength camera and a versatile cryogenic platform that can be easily modified to allow the installation of alternative continuum or on-chip spectrometer arrays using different optics, filtering, detector geometries, materials and technologies that can operate at different frequencies.
MUSCAT is a new platform for mm/sub-mm astronomy at the 50m LMT. It is currently configured for 1.1 mm continuum observations with a focal plane consisting of 1458 feedhorn-coupled LEKIDs read out over six frequency division multiplexed RF readout chains with ~250 detectors per readout. We present the performance of the detector readout and tuning system following the initial on-sky commissioning campaign in late 2021. We give details of the readout hardware, the instrument control software, the interfaces between the instrument and telescope control systems, and the automated tuning system for maintaining background-limited performance over the course of an observing night given the varying atmospheric load.
The Mexico-UK Submm Camara for Astronomy (MUSCAT) is a 1.1 mm receiver comprising 1458 Horn-Coupled Lumped Element Kinetic Inductance Detectors (LEKIDs) built through a collaborative effort led by Cardiff University in the UK and the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) in Mexico. MUSCAT was successfully installed on the 50 m diameter Large Millimeter Telescope (LMT) Alfonso Serrano, in December 2021
Here we provide an overview of the MUSCAT platform and present on-sky engineering tests results from scientific commissioning data.
The Mexico-UK Submillimetre Camera for AsTronomy (MUSCAT) is a 1.1 mm receiver consisting of 1,500 lumped-element kinetic inductance detectors (LEKIDs) for the Large Millimeter Telescope (LMT; Volcán Sierra Negra in Puebla, México). MUSCAT utilises the maximum field of view of the LMT's upgraded 50-metre primary mirror and is the first México-UK collaboration to deploy a millimetre/sub-mm receiver on the Large Millimeter Telescope. Using a simplistic simulator, we estimate a predicted mapping speed for MUSCAT by combining the measured performance of MUSCAT with the observed sky conditions at the LMT. We compare this to a previously calculated bolometric-model mapping speed and find that our mapping speed is in good agreement when this is scaled by a previously reported empirical factor. Through this simulation we show that signal contamination due to sky fluctuations can be effectively removed through the use of principle component analysis. We also give an overview
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