ALMA, the Atacama Large Millimeter/submillimeter Array, is the largest astronomical project in existence. The ALMA site, some 50 km east of San Pedro de Atacama in northern Chile, is in one of the driest places on Earth. Astronomers find unsurpassed conditions for observing, but they must operate a frontier observatory under very difficult conditions. Chajnantor is more than 750 m higher than the observatories on Mauna Kea, and 2400 m higher than the VLT on Cerro Paranal.
 

Photo: Artist's impression of the ALMA site.

ALMA is a leg of Around the World in 80 Telescopes tour: Click to play; click  (lower right) to view video full screen Next stop: EVN (previous stop: APEX)

ALMA will be a single telescope of revolutionary design, composed initially of 66 high-precision antennas, and operating at wavelengths of 0.3 to 9.6 mm. Its main 12-metre array will have fifty antennas, 12 metres in diameter, acting together as a single telescope — an interferometer. An additional compact array of four 12-metre and twelve 7-metre antennas will complement this. The antennas can be moved across the desert plateau over distances from 150 metres to 16 kilometres, which will give ALMA a powerful variable "zoom". It will be able to probe the Universe at millimetre and submillimetre wavelengths with unprecedented sensitivity and resolution, with a vision up to ten times sharper than the Hubble Space Telescope, and complementing images made with the VLT Interferometer.

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