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Last Updated: Monday, 30 July 2007, 22:09 GMT 23:09 UK
Giant truck set for sky-high task
Transporter  Image: Eso
The transporter is 20m long and has 28 wheels

A colossal 28-wheel truck that will help build a major telescope array in the Chilean Andes has successfully passed a series of tests.

The giant vehicle will heave antennas - each weighing 115 tonnes - up a mountainside to the site of the array, a plateau 5,000m above sea level.

The Alma telescope will study the night sky at sub-millimetre wavelengths.

Astronomers say Alma will illuminate one half of the Universe that has hitherto been shrouded in darkness.

That entire mechanism has to be tested very carefully with dummy weights, as well as the independent steering of the wheels
Adrian Russell, Alma project manager, North America
Alma stands for the Atacama Large Millimeter Array.

When it is completed in 2012, the 470m ($900m) array will be able to observe some of the first galaxies to form after the Big Bang, and catch planets in the act of forming around young stars.

The telescope project will initially comprise 66 high-precision antennas, installed at the high-altitude Llano de Chajnantor site in Chile's Atacama desert.

Each antenna has a dish measuring about 12m across and a surface engineered to be accurate to within 20 microns (millionths of a metre).

Power and precision

The dishes will be electronically combined to provide astronomical observations which are equivalent to a single large telescope of tremendous size and resolution.

Alma will be able to probe the Universe at millimetre and sub-millimetre wavelengths with unprecedented sensitivity and resolution, with an accuracy up to ten times better than the Hubble Space Telescope.

The antenna transporter is 10m wide, 20m long and 6m high. It weighs 130 tonnes and has as much power as two Formula 1 engines.

The transporter is powerful enough to carry a 115-tonne antenna

The first of two vehicles has been put through its paces at the firm Scheuerle Fahrzeugfabrik near Stuttgart in Germany.

The custom-built colossus will be able to transport a 115-tonne antenna and set it down on a concrete pad within millimetres of a prescribed position.

Engineers have tested whether the transporter can safely pick up the 115-tonne antenna and very carefully settle it back down again.

"As it picks up the antenna, the transporter puts its arms under the armpits of the antenna, lifts it up and pulls it slowly up a ramp. It gradually lifts the antenna higher and higher and eventually pulls it right into the vehicle," said Adrian Russell, Alma project manager for North America.

"When it gets to where the antenna is being relocated, the antenna very slowly and carefully slides back down the ramp so it is overhanging the edge of the vehicle.

On top of the world

He told the BBC News website: "It can then be manipulated left and right, and slowly lowered on to the antenna foundation. That entire mechanism has to be tested very carefully with dummy weights, as well as the independent steering of the wheels."

Each antenna has a dish measuring 12m across and weighs 115 tonnes

The vehicles will have to haul their heavy cargo safely from the 2,900m-high Alma base camp, where the antennas are assembled, to the array site, which lies at 5,000m - about half the cruising altitude of a 747.

The vehicles must therefore be extremely powerful, as the journey will make extraordinary demands on the two 500kW diesel engines.

Because of the low oxygen content of the air at 5,000m, vehicle operators will need to wear portable oxygen canisters. The backrests of the driver seats are shaped to allow the driver to wear his oxygen tank while driving.

Llano de Chajnantor was chosen as the site for Alma because it is so dry. Water vapour absorbs sub-millimetre waves, interfering with observations using the telescope.

If all the water vapour above Chajnantor were collected, it would form a pool just 1mm deep.

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30 May 07 |  Science/Nature
'Alma' sets new heights for astronomy
07 Aug 06 |  Science/Nature
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07 Aug 06 |  Science/Nature
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17 Jul 06 |  Magazine
Powerful telescope set for Chile
22 May 06 |  Science/Nature

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