The Atacama Large Millimeter Array (ALMA) is a joint project between North America and Europe to build and operate the world's largest, most powerful telescope operating at millimeter and sub-millimeter wavelengths. This news release, "Astronomers break ground for unique telescope," gives us some details about the project which should be completed by 2011.
ALMA -- the Atacama Large Millimeter Array -- will be a single instrument composed of 64 high-precision antennas located on the Chajnantor plain of the Chilean Andes in the District of San Pedro de Atacama, 16,500 feet (5,000 meters) above sea level. ALMA's primary function will be to observe and image with unprecedented clarity the enigmatic cold regions of the Universe, which are optically dark, yet shine brightly in the millimeter portion of the electromagnetic spectrum.
Here is a conceptual artist rendering of the ALMA telescope (Credit: European Southern Observatory (ESO)).
Why will be ALMA built that high?
The millimeter and sub-millimeter radiation that ALMA will study is able to penetrate the vast clouds of dust and gas that populate interstellar and intergalactic space, revealing previously hidden details about astronomical objects. This energy, however, is blocked by atmospheric moisture here on Earth. To conduct research in this critical portion of the spectrum, astronomers need a site that is very dry, and preferably at a very high altitude where the atmosphere is thinner. Extensive tests showed that the sky above the high-altitude Chajnantor plain in the Atacama Desert has the unsurpassed clarity and stability needed to perform efficient observations with ALMA.
Here are some more details about the physical reconfigurable installation.
ALMA will be composed of 64 high-precision antennas, each 12 meters in diameter. The ALMA antennas can be repositioned, allowing the telescope to function much like the zoom lens on a camera. At its largest, ALMA will be 14 kilometers (8.7 miles) across. This will allow the telescope to observe the fine-scale details of astronomical objects. At its smallest, approximately 150 meters (492 feet) across, ALMA will be able to study the large-scale structures of these same objects.
Such a telescope will generate lots of data. Let's look at some juicy numbers.
With 64 antennas, ALMA will generate 2016 individual antenna pairs (baselines) during its observations. To handle this much data, ALMA will rely on a very powerful, specialized computer called a correlator, which will perform 16,000 million-million operations per second.
[Note: I looked at the ALMA Correlator page, but I'm unable to figure how they arrive to this number of operations per second. Any clues?]
For more information, check the Atacama Large Millimeter Array website or the ALMA Project at ESO.
A last bit of information; I borrowed the title of this column from this page on the National Science Foundation website.
Source: National Radio Astronomy Observatory News Release, via Spaceflight Now, November 9, 2003
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