Large Millimeter Telescope

Large Millimeter Telescope

Alternative names	LMT
Part of	Event Horizon Telescope
Location(s)	Sierra Negra
Coordinates	18°59′09″N 97°18′53″W / 18.985833333333°N 97.314722222222°W / 18.985833333333; -97.314722222222
Organization	National Institute of Astrophysics, Optics and Electronics University of Massachusetts Amherst
Altitude	4,640 m (15,220 ft)
Built	2001–2010 (2001–2010)
First light	17 June 2011
Telescope style	Cassegrain reflecting telescope radio telescope
Diameter	50 m (164 ft 1 in)
Secondary diameter	2.5 m (8 ft 2 in)
Collecting area	1,960 m2 (21,100 sq ft)
Focal length	525 m (1,722 ft 5 in)
Mounting	altazimuth mount
Website	www.lmtgtm.org
Location of Large Millimeter Telescope
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The Large Millimeter Telescope (LMT) (Spanish: Gran Telescopio Milimétrico, or GTM), officially the Large Millimeter Telescope Alfonso Serrano (Spanish: Gran Telescopio Milimétrico Alfonso Serrano), is the world's largest single-aperture telescope in its frequency range, built for observing radio waves in the wave lengths from approximately 0.85 to 4 mm. It has an active surface with a diameter of 50 metres (160 ft) and 1,960 square metres (21,100 sq ft) of collecting area.^[1]

The telescope is located at an altitude of 4,850 metres (15,910 ft) on top of Sierra Negra, the fifth-highest peak in Mexico and an extinct volcanic companion to Mexico's highest mountain Pico de Orizaba, inside the National Park Pico de Orizaba in the state of Puebla. It is a binational Mexican (70%) – American (30%) joint project of the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) and the University of Massachusetts Amherst.

Millimetre-wavelength observations using the LMT give astronomers a view of regions which are obscured by dust in the interstellar medium, thus increasing our knowledge of star formation. The telescope is also particularly fitted for observing solar system planetesimals and planets as well as extra-solar protoplanetary disks which are relatively cold and emit most of their radiation at millimetre wavelengths.^[2]

The mission of the LMT is to: 1) pursue pioneering research, 2) train future generations of scientists and engineers, and 3) develop new technology for the benefit of society.^[3] The LMT mainly studies thermally cold objects, most of which are associated with large amounts of cosmic dust and/or molecular gas. Among the objects of interest are comets, planets, protoplanetary discs, evolved stars, star-forming regions and galaxies, molecular clouds, active galactic nuclei (AGNs), high-redshift galaxies, clusters of galaxies, and the cosmic microwave background.^[4]

The LMT has a bent Cassegrain optical system with a 50m-diameter reflecting primary surface (M1) formed by 180 segments distributed in five concentric rings. The number of segments in the rings, from the center of the dish to the outside, are: 12, 24 and 48 in the three outermost rings. Each segment is connected to the structure of the telescope through four actuators, allowing for an active reflecting primary surface. In addition, each segment is formed by eight precision electro-formed nickel sub-panels. The reflecting secondary surface (M2) has a 2.6-m diameter, also built by nine electro-formed nickel sub-panels, and is attached to the telescope with an active hexapod that allows precise focus, lateral offsets, and tilts. The hexapod is attached to the telescope through a metal tetrapod. Finally, the reflecting tertiary surface (M3) is almost flat, elliptical with a 1.6-m major axis and delivers the light beam to the receivers.^[5]