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Scanning the entire sky, for the first time

In the daytime the view from Cerro Pachon, a rocky, desolate peak high above Chile, offers a breathtaking vista of the Andes. Mountains of rock topped with snow and glaciers seem to touch the heavens.

Come nightfall, the Andes disappear into gloom and then the real show begins. As if someone had flicked a switch, the gleam of millions of planets and stars studs the inky blackness overhead.

The sky seems too immense to absorb, even for giant telescopes. They focus on one tiny portion at a time, pinpricks in the cosmos, because traditionally astronomers like to dwell on detail.

Not any more. Cerro Pachon is to host the Large Synoptic Survey Telescope (LSST), a near $400 million project that will survey the entire sky several times a week — something never done before.

Every 15 seconds it will take an image seven times the diametre of the moon, adding up, every three days, to a full panorama of the heavens. Boasting 3,200 megapixels, it will be the world’s biggest digital camera.

“Most telescopes look at a tiny part of the sky, to look deep and in detail. We want to look broadly, to cover everything,” Victor Krabbendam, the deputy project manager, said.

This week the telescope took a step closer to reality after donations from two geeky philanthropic billionaires who are entranced by the technology and its possibilities.

Bill Gates gave $10 million from his private fortune and a former Microsoft colleague, Charles Simonyi, gave $20 million through his Fund for Arts and Sciences.

“LSST is truly an internet telescope which will put terabytes of data each night into the hands of anyone that wants to explore it. [It is] a shared resource for all humanity — the ultimate network peripheral device to explore the universe,” Mr. Gates said.

The donations will keep on track the construction of three large mirrors and three refractive lenses which are the most important and expensive part of the machine.

The first stages of production for the two largest mirrors are under way at the Mirror Laboratory at the University of Arizona.

Launched in 2000, the project is a partnership based in Tucson, Arizona, and split among 23 universities, laboratories and private entities. Once the mirrors are ready they will be hauled up the 2,690-metre peak and installed in a dome due for construction in 2011. “First light,” as astronomers call their scoping, should begin four years later.

The camera is expected to take more than 200,000 pictures. Processing that information is expected to be the most technically difficult part of the project.

The camera’s 15 second exposure should be long enough to record images of even very faint objects such as asteroids and so-called near-Earth objects. By monitoring them night after night, it should be possible to infer their orbit around the sun and hence how likely they are to slam into Earth.

The LSST will also be useful for basic science. Its time-lapse images can be used to create 3D maps of the mass distribution in the universe. That should not only help to trace billions of galaxies, but also tell cosmologists more about the mysterious and recently discovered “dark energy” that is driving the expansion of the universe. — © Guardian Newspapers Limited, 2008

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