Instead of building one giant dish, ALMA consists of many dishes
Astronomers in Chile have just fired up the ALMA radio telescope array for the very first time. ALMA is destined to be the largest, most expensive, and most powerful telescope array on the planet, and when the array of 66 telescopes is completed in 2013, ALMA will be able to resolve images of galaxies that are an incredible ten times sharper than the best that we can get from Hubble.
ALMA isn’t the kind of telescope that you can look through, and it’s not the kind of telescope that sends back pictures of what we’d see if only our eyeballs were powerful enough. ALMA stands for “Atacama Large Millimeter Array,” and it’s a bunch of different radar telescopes all working together to to resolve incredibly small astronomical features in wavelengths of light that are invisible to conventional telescopes.
Instead of building one giant dish, ALMA consists of many dishes — currently 12, eventually 66 — all working in concert. By precisely measuring the positions of the dishes and correlating their data signals within a millionth of a millionth of a second, a supercomputer can combine the data from all of the telescopes at once to one single incredibly detailed image of the sky, picking out clouds of hydrogen where stars are forming, and possibly even images of other solar systems.
Part of what makes ALMA so versatile is that each telescope can be picked up and carted around to dynamically reconfigure the array. Because of the way the cooperating telescopes work, having lots of them close together gives you a sort of wide-angle lens, and if you want to zoom in on something, you need the individual telescopes to be as far from each other as possible. Each of ALMA’s 115-ton, 40-foot-wide dishes can be picked up by a customized transporter vehicle (pictured below) and moved around depending on what kind of observations you’re going for, and the array can be repositioned into widths anywhere from 500 feet to 10 miles.
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