Moving towards daytime observing at the Large Millimeter Telescope

The Large Millimeter Telescope Alfonso Serrano (LMT) is a 50m-diameter radio telescope for millimeter-wave astronomy. In this paper we describe a number of initiatives underway to upgrade the antenna systems and permit scientific observations during daylight hours. We summarize recent efforts to characterize the thermal gradients that occur within the LMT structure and to identify important modes of surface deformation. The mitigation program involves use of the LMT's active surface to counteract the effects of measured thermal gradients within the antenna structure. It also includes active measures such as the installation of a ventilation system in the antenna backup structure. Prospects for additional active metrology measurements of the antenna surface for real-time surface corrections are also discussed.

[1]  A. Reichold,et al.  Multi-channel absolute distance measurement system with sub ppm-accuracy and 20 m range using frequency scanning interferometry and gas absorption cells. , 2014, Optics express.

[2]  R. Hills,et al.  Measurement of antenna surfaces from in- and out-of-focus beam maps using astronomical sources , 2006, astro-ph/0612241.

[3]  F. P. Schloerb,et al.  Calibration and operation of the active surface of the Large Millimeter Telescope , 2016, Astronomical Telescopes + Instrumentation.

[4]  A. Greve,et al.  Thermal control of the IRAM 30-m millimeter radio telescope , 1988 .

[5]  Joseph Antebi,et al.  Active segmented primary reflector and pointing accuracy of the Large Millimeter Telescope (LMT) , 1998, Astronomical Telescopes and Instrumentation.

[6]  Axel Nothnagel,et al.  Terrestrial Laser Scanner Two-Face Measurements for Analyzing the Elevation-Dependent Deformation of the Onsala Space Observatory 20-m Radio Telescope’s Main Reflector in a Bundle Adjustment , 2017, Sensors.

[7]  H. Kuhlmann,et al.  Aiming at self-calibration of terrestrial laser scanners using only one single object and one single scan , 2014 .

[8]  A. Greve,et al.  Improvement of the IRAM 30-m telescope from temperature measurements and finite-element calculations , 2005, IEEE Transactions on Antennas and Propagation.

[9]  D. H. Hughes,et al.  Reporting the first 3 years of 225-GHz opacity measurements at the site of the Large Millimeter Telescope Alfonso Serrano , 2016, Astronomical Telescopes + Instrumentation.

[10]  A. Greve,et al.  Thermal behavior of millimeter wavelength radio telescopes , 1992 .

[11]  F. Peter Schloerb,et al.  Photogrammetry mapping and alignment of the LMT 50-meter primary reflector , 2018, Astronomical Telescopes + Instrumentation.

[12]  Andrew Rakich,et al.  A 3D metrology system for the GMT , 2016, Astronomical Telescopes + Instrumentation.

[13]  Marty Bloss,et al.  LASSI: keeping the Green Bank Telescope in shape , 2020 .

[14]  R. Hills,et al.  Out-of-focus holography at the Green Bank Telescope , 2006, astro-ph/0612249.