December 19, 2008
ALMA Equipped With First Antenna
High in the Atacama region in northern Chile, one of the world's most advanced telescopes has just passed a major milestone. The first of many state-of-the-art antennas has just been handed over to the Atacama Large Millimeter/submillimeter Array (ALMA) project. ALMA is under construction on the plateau of Chajnantor, at an altitude of 5000 m. The telescope is being built by a global partnership, including ESO as the European partner.
ALMA will initially comprise 66 high precision antennas, with the option to expand in the future. There will be an array of fifty 12-metre antennas, acting together as a single giant telescope, and a compact array composed of 7-metre and 12-metre diameter antennas.
The first 12-metre diameter antenna, built by Mitsubishi Electric Corporation for the National Astronomical Observatory of Japan, one of the ALMA partners, has just been handed over to the observatory. It will shortly be joined by North American and European antennas.
"Our Japanese colleagues have produced this state-of-the-art antenna to exacting specifications. We are very excited about the handover because now we can fully equip this antenna for scientific observations," said Thijs de Graauw, ALMA Director.
Antennas arriving at the ALMA site undergo a series of tests to ensure that they meet the strict requirements of the telescope. The antennas have surfaces accurate to less than the thickness of a human hair, and can be pointed precisely enough to pick out a golf ball at a distance of 15 km.
"ALMA is very important to European astronomers and to ESO, the European partner in this project, because it allows us to look at the Universe in a way that has never been possible before. It really marks the start of a new era in astronomy," said Wolfgang Wild, the European ALMA Project Manager.
This antenna handover is a major milestone, as the observatory team can now proceed with integrating the rest of the components, including the sensitive receivers that will collect the faint cosmic signals from space.
The antennas are tested at the Operations Support Facility, at an altitude of 2900 m, before being moved to the plateau of Chajnantor at 5000 m. The Operations Support Facility will also be the observatory's control centre.
ALMA is being built on the Chajnantor plateau, high in the Chilean Andes, because the site's extreme dryness and altitude offer excellent conditions for observing the submillimeter-wavelength signals for which the telescope is designed.
In addition, the wide plateau at Chajnantor offers ample space for the construction of the antenna array, which is spread out and linked together over distances of more than 16 kilometers.
"The ALMA antennas must withstand the harsh conditions at Chajnantor with strong winds, cold temperatures and a thin atmosphere with half as much oxygen as at sea level. This forbidding environment also poses challenges for the workers building ALMA," said de Graauw.
The antennas, which each weigh about 100 tons, can be moved to different positions in order to reconfigure the ALMA telescope. This will be carried out by two custom-designed transporters, each of which is 10 meters wide, 20 meters long, and has 28 wheels.
The ALMA Project is a partnership between the scientific communities of East Asia, Europe and North America with Chile.
ALMA will be the leading astronomical instrument for observing the cool Universe "“ the molecular gas and dust that constitute the building blocks of stars, planetary systems, galaxies and of life itself.
ALMA will operate at wavelengths of 0.3 to 9.6 mm. At these wavelengths, a high, dry site is needed for the telescope to be able to see through the Earth's atmosphere. This is why ALMA is being built on the 5000 m high plateau of Chajnantor in the Atacama region of Chile. ALMA will offer unprecedented sensitivity and resolution. The 12-metre antennas will have reconfigurable baselines ranging from 15 m to 16 km. Resolutions as fine as 0.005 arcseconds will be achieved at the shortest wavelengths "“ a factor of ten better than the Hubble Space Telescope.
The ALMA project is a partnership between Europe, Japan and North America in cooperation with the Republic of Chile. ALMA is funded in Europe by ESO, in Japan by the National Institutes of Natural Sciences in cooperation with the Academia Sinica in Taiwan and in North America by the U.S. National Science Foundation in cooperation with the National Research Council of Canada. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of Japan by the National Astronomical Observatory of Japan and on behalf of North America by the National Radio Astronomy Observatory, which is managed by Associated Universities, Inc.
Image Caption: The first ALMA antenna to be handed over to the observatory, pictured here at the ALMA Operations Support Facility. This state-of-the-art 12 m diameter antenna was manufactured by Mitsubishi Electric Corporation. Credit: ALMA (ESO/NAOJ/NRAO).
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