AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 9. Ground Based Instrumentation
Display, Monday, May 31, 1999, 9:20am-6:30pm, Southwest Exhibit Hall

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[9.15] The Large Millimeter Telescope (LMT)

J.W.M. Baars (LMT Project-UMass/INAOE), L. Carrasco (INAOE), F.P. Schloerb (FCRAO/UMass)

The University of Massachusetts at Amherst, through the FCRAO, and the Instituto Nacional de Astrofisica, Optica y Electronica (INAOE) in Puebla, Mexico, are collaborating in the design, construction and joint operation of the Large Millimeter Telescope (LMT). The LMT is a full aperture telescope of 50 m diameter for operation to a shortest wavelength of 1 mm. First generation facility instruments include a 32-channel spectroscopy receiver for the 85-115 GHz band and a 144-channel bolometer system at 250 GHz. A joint institute, the LMT Observatory, will operate the telescope for the astronomers from the participating institutes and outside observers. Commissioning of the LMT is scheduled to start in 2001. The LMT is expected to contribute in particular to the study of the Universe at high redshifts. Its size and southern location also make it a powerful member of the growing mm-wavelength VLBI activity. The LMT is located on Cerro la Negra in Central Mexico at 4600 m altitude and a latitude of 19 degrees. The site is 100 km east of Puebla. The opacity shows median tau-values of less than 0.15 at 230 GHz from Sep through May, good for operation to 300 GHz. Site preparation and installation of utilities is under way. Work on the telescope foundation will begin in Spring 1999 with steel assembly expected to commence in early 2000. The LMT is being designed by MAN Technologie. It is an exposed, alt-azimuth antenna with a wheel-on-track azimuth drive and double bull-gear elevation drive. An advanced servo-system will aid in achieving the pointing accuracy of 1''. A spacious receiver cabin behind the reflector, allows the deployment of and easy access to several receiver systems. The reflector is a space-frame structure, supporting 130 reflector subframes of about 5x3 m2 which carry the reflector surface panels. The subframes are supported on actuators to enable real-time correction of the reflector surface for deformations, caused by gravity, temperature gradients and the quasi-static wind component. The surface accuracy specification is 75 micrometers. The pointing goal of 0.6'' will be reached with an optical system under development at UMass, in collaboration with MIT-Lincoln Laboratory.

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