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Last Updated: Monday, 17 July 2006, 10:55 GMT 11:55 UK
The next best place to space
Atacama dessert
The distinctly Mars-like location of the Very Large Telescope

By Sean Blair

The returning space shuttle crew have been enjoying rare views of our planet from orbit, but star-gazers seeking breath-taking views of the cosmos without leaving Earth head for a remote mountain top in South America that even looks a bit like Mars.

The journey is somewhat less hi-tech than a trip into space but almost as demanding.

Star-gazers on a quest for extraordinary images of the cosmos through the unassumingly named Very Large Telescope must first endure a bumpy two-hour drive from the Chilean town of Antofagasta.

And given the remoteness of their destination, like astronauts, they too are filled with a sense of leaving the outside world.

For astronomers starting shift at the VLT, as it's known in the star-gazing fraternity, undeniably work in one of the harshest and most remote environments short of an alien planet.

The VLT is located on the flattened peak of Cerro Paranal, a 2,635m-high mountain in the Atacama Desert, one of the driest places on Earth - 50 times drier than California's Death Valley. Its boulder-littered red sand is entirely without vegetation.

Spiral Galaxy Messier 100 (Image: Eso)

It is dry and sterile enough that the Atacama has been used as an analogue for Mars in Nasa studies, but even so, around 120 astronomers, engineers and support staff work here at a time.

Modern observatories go to where the stars are, and Paranal's high-altitude, low-humidity and extreme remoteness give it some of the clearest skies in the world.

"The stability of the climate here helps make the VLT the most productive visible-light observatory in the world," says VLT astronomer Olivier Hainaut. "We are operational 87% of the time, while comparable facilities are 'weathered-out' much more often."

Despite its name, the VLT is actually a collection of four 8.2m-diameter telescopes and three 1.8m telescopes, with an additional 1.8m telescope and two wide-angle survey telescopes due to begin operations by the year's end.

Built and operated by the European Southern Observatory (Eso) - an inter-governmental organisation that includes the UK - the VLT telescopes either operate independently or together as an array, their light combined together to provide maximum angular resolution equivalent to a single 200m telescope, theoretically sufficient to detect an astronaut on the Moon.

On average a new scientific paper based on VLT results is published daily. And in 2005 the observatory made history by acquiring the first direct image of an "exoplanet" outside our solar system.

Living quarters (Credit: Esther Solis)
Tropical garden and swimming pool under the Residencia dome
Unfortunately, optimal conditions for star-gazing are not ideal for human beings. So just like astronauts in orbit, the Eso has brought along its own environment for comfortable living and working.

Staff are based in a semi-subterranean building called the Residencia, which includes a swimming pool and tropical garden to maintain interior humidity, topped by a 35m glass dome.

Resembling a cross between a Bond villain's hide-out and a university hall of residence, the four-storey Residencia also contains more than 100 bedrooms, a cinema, library, gym and cafeteria. It is part of a "base camp" 4km away from the VLT, although the dry air makes everything look much closer.

"We generate our own electricity here, but other than that we are completely dependent on the outside world," says logistics supervisor Kiriako Markar. "Two truckloads of water are delivered every second day and fuel for our three generators is driven in once a week."

The camp has its own paramedic team and an ambulance, with a helipad on site for the most serious medical emergencies.

'Spectacular skies'

"It is Eso policy that no-one stays here for more than 10 days - two weeks maximum," explains Markar. "That's more for psychological than physical reasons - it isn't good for people to be cooped up for too long seeing just the same people and surroundings."

Paranal (Eso)
The clutch of telescopes that make up the VLT (Image: Eso)
The VLT is a 24-hour operation. During daylight hours, engineers perform maintenance work, then as night approaches it is the astronomers' turn. The telescope buildings themselves stay empty for the night, their delicate mechanisms being vulnerable to vibrations and temperature shifts a human presence might cause.

Operated remotely, their protective doors open and the telescopes glide smoothly to line up with the first of their assigned targets. Their mirrors are continually adjusted by computer-controlled actuators to adjust for atmospheric turbulence.

"We call this adaptive optics, and it effectively lifts the VLT into space," says Hainaut. "We can see our targets so clearly it is as though the atmosphere has been removed."

Another way the astronomers move closer to space is by imposing strict controls on light pollution. The site itself follows blackout regulations worthy of the London Blitz: all windows stay covered, a canopy extends over the Residencia dome and all cars are driven using parking lights only.

Even to the naked eye, the result is some of the most spectacular night skies anywhere, with the bright bar of the Milky Way interrupted by dark clouds shielding our galactic centre. The telescope views are recorded by light detectors cooled to near absolute zero for maximum sensitivity.

At the end of their 10-day shifts at the next best place to space, VLT staff return to the outside world to enjoy different kinds of novel views: "The colours," says Markar. "When you get back, it is the variation of colours that you appreciate the most."

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