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.
Microwave kinetic inductance detectors (MKIDs) are increasingly used in ground-based (sub)millimeter-wave astronomy experiments. Two existing challenges to operating detector arrays remain in selecting excitation tones for each MKID where there are hundreds of resonators on the same feedline or network and that will yield the best combination of linearity and sensitivity. This is further complicated when operating arrays at ground-based telescopes, where variations in background loading from the atmosphere can induce significant shifts in MKID resonant frequencies and affect quality factors. We describe a quantitative method for optimal tuning of MKID arrays under dynamic loading conditions. We apply this new readout tuning technique to the 1.1 mm MKID array of the TolTEC camera at the Large Millimeter Telescope, where we incrementally change the readout power applied to investigate its effect. We perform in lab optical characterization of a CCAT Observatory MKID array to investigate optimal tuning under different loading conditions.
The TolTEC Camera, mounted on the Large Millimeter Telescope (LMT), is a 3-band continuum camera and polarimeter operating at millimeter wavelengths. This paper reviews our progress on the camera commissioning and its inaugural scientific programs, spanning the 2022/2023 commissioning phases and reviewing the winter 2024 science program. We report on mapping speed estimations, optical performance, and the first scientific imaging and polarimetry findings. Additionally, advancements in out-of-focus holography and the integration of two novel maximum likelihood mapmakers are discussed. We conclude with scientific forecasts for the first four TolTEC Legacy Surveys and an overview of the initiatives aimed at facilitating public access to the camera and the broader LMT infrastructure.
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.
The Large Millimeter Telescope (LMT) Alfonso Serrano is a bi-national (Mexico and USA) telescope facility constructed on the summit of Sierra Negra, at an altitude of 4600m, in the Mexican state of Puebla. The LMT is a 50-m diameter single-dish telescope, with an active surface control-system to correct gravitational and thermal deformations of the primary reflector, designed and optimized to conduct scientific observations using heterodyne and continuum receivers, as well as VLBI observations, at frequencies between ~70 and 350 GHz. We describe the current status and technical performance of the recently commissioned LMT 50-m, the instrumentation development program, and future engineering upgrades that will optimize the optical efficiency of the telescope and increase its scientific productivity.
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