July 31st, 2007
How to carry a telescope
Obviously, it depends on its size. But here I’m speaking about the ALMA (Atacama Large Millimeter/submillimeter Array) which will be fully operational in 2012 and will be composed initially of 66 high-precision telescopes. These 12-meter submillimeter quality antennas will weigh about 115 tons and be installed at an altitude of about 5,000 meters. Now, the first ALMA antenna transporter has been successfully tested. Even if it’s not the world’s biggest truck, this is still a ‘colossus on wheels.’ This 28-wheel truck is 10 meters wide, 20 meters long and 6 meters high, weighs 130 tons and has as much power as two Formula 1 engines. It should be operational by the end of 2007.
You can see above an “artist’s rendering of an ALMA antenna being transported from the base camp to the 5000m high observing site. The transporter can move with a maximum speed of 12 km/h when loaded with a 115-ton antenna.” (Credit: Unknown artist, for ESO) Here is a link to several other images of this big truck.
Before looking at the truck itself, here are some details about the ALMA project. “The ALMA Project is a giant, international observatory currently in construction on the high-altitude Chajnantor site in Chile, and composed initially of 66 high-precision telescopes, operating at wavelengths of 0.3 to 9.6 mm. The ALMA antennas will be electronically combined and 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 submillimetre wavelengths with unprecedented sensitivity and resolution, with an accuracy up to ten times better than the Hubble Space Telescope, and complementing images made with ESO’s Very Large Telescope Interferometer.”
For more details, you can visit the Atacama Large Millimeter Array website or read the ALMA brochure (PDF format, 8 pages).
Now, let’s look at some of the technical challenges that the engineers had to solve when they’ve designed these big trucks. The 115-ton antennas will have to be moved from a base camp located at an altitude of 2,900 meters to the high-altitude desert Chajnantor plateau located an an at an altitude of 5,000 meters. Then, the antennas will be sometimes redeployed to allow different observing modes. The telescopes will be separated by distances going from 150 meters to 15 kilometers. And they will need to be installed within millimeters of a desired position to be efficient. Finally, the engineers had to think about how to deliver oxygen to the truck drivers at such an altitude.
So how did they solve all these challenges? “Each transporter has a mass of 130 tons and is able to lift and transport antennas of up to a weight of 115 tons. The transporters have to position the antennas on the docking pads with precision in the millimetre range. On the other hand, the transporters must be powerful enough to reliably and safely climb from an altitude of 2900 m to 5000 m with their heavy and valuable load, putting extraordinary demands on the two 500 kW diesel engines.”
It’s also important to note that these engines are less powerful at high altitude. “At the high altitude site of 5000 m, the two engines will lose about half of their power (compared to sea level) because of the reduced oxygen content on the air. The ALMA transporters will be able to move at the speed of 20 km/h when empty and 12 km/h when loaded with an antenna. The transporters can be driven from the cabin like a truck, or from a portable panel like a toy car.”
And what about the drivers? “The human factor was also considered. For example, the backrests of the driver seats are shaped to allow the driver to wear his oxygen tank while driving.” I sure hope they will be well paid.
Sources: European Organisation for Astronomical Research in the Southern Hemisphere news release, July 30, 2007; and various websites
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