High in the Atacama region in northern Chile, one of the world’s most advanced telescopes passed a milestone recently. The first of many state-of-the-art antennae has 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 3 miles (5 kilometers). The telescope is being built by a global partnership and the European Southern Observatory (ESO) represents the European partner.
ALMA will initially comprise 66 high-precision antennae, with the option to expand in the future. There will be an array of fifty 40-foot (12m) antennae, acting together as a single giant telescope, and a compact array composed of 23-foot (7m) and 40-foot (12m) diameter antennae.
ALMA will help astronomers study the cool universe – the molecular gas and tiny dust grains from which stars, planetary systems, galaxies and even life are formed. ALMA will provide new insights into the formation of stars and planets, and will reveal distant galaxies in the early universe, which we see as they were more than 10 billion years ago.
The Mitsubishi Electric Corporation built the first 40-foot (12m) diameter antenna for the National Astronomical Observatory of Japan, one of the ALMA partners. North American and European antennae will join the first antenna shortly.
“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.
Antennae arriving at the ALMA site undergo a series of tests to ensure that they meet the strict requirements of the telescope. The antennae 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 9 miles (15 km).
“ALMA is very important to European astronomers and to ESO, 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.
The observatory team now can proceed with integrating the rest of the components, including the sensitive receivers that will collect the faint cosmic signals from space.
The antennae are tested at the Operations Support Facility, at an altitude of 1.8 miles (2.9 km), before being moved to the plateau of Chajnantor at 3 miles (5 kilometers). The Operations Support Facility will also be the observatory’s control center.
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, Chajnantor’s wide plateau offers ample space for the construction of the antenna array, which is spread out and linked together over distances of more than 10 miles (16 km).
“The ALMA antennae 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.
Each antenna weighs about 100 tons and can be moved to different positions to reconfigure the ALMA telescope.