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The successful flight was a first test for the Sunrise mission, which aims to take the best pictures yet captured of the Sun.

Those snaps will be used to help understand the chaotic solar magnetic field, which can trigger stormy ‘space weather’ that sometimes wreaks havoc on satellites.

The scientists involved say that they hope the mission’s success will herald a new enthusiasm for cheap but high-flying astronomical balloons, which have been overlooked by space agencies in past decades.

Sunrise’s first science flight is planned for June 2009, when a balloon, carrying a one-metre telescope, will launch from Sweden and float to a height of 37 kilometres. Stratospheric winds will usher it along a two-week, sun-drenched route around the Arctic Circle.

The telescope, mounted with steadying equipment to remove jitters from the camera work, should be able to take pictures of features on the Sun’s surface as small as 30 kilometres across.

That is four times better than the best solar telescope in space, and twice as good as the best on Earth, says Michael Knolker, director of the High Altitude Observatory at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado.

NCAR is running the project along with NASA and several European partners. Knolker is particularly interested in studying faculae: intensely magnetic bright spots on the Sun’s surface whose swirling motions highlight the Sun’s turbulent magnetic field.

In times of increased activity, streams of magnetised plasma can shoot from these faculae toward Earth, causing stormy space weather.

“It can induce rather strong (electric) currents in satellites, that have led, in various instances, to satellites being fried,” he says.

The test flight, which took place on October 3 at the Columbia Scientific Balloon Facility in Fort Sumner, New Mexico, was a success, says test-flight project manager David Elmore. Engineers only partly filled the plastic balloon with helium, since the gas expands in the rarified air of the stratosphere.

The 20-micrometre-thick balloon, thinner than human hair but as heavy as the gondola itself, rose at a speed of 18 kilometres an hour. After shedding some 100 kilograms of ballast, the balloon settled in calm 12 knot winds at an altitude of 37 kilometres. The cold affected the electronics more than expected, Elmore says.

At -70 degrees Celsius, several electronics units failed. Engineers could not get a high-speed telemetry connection to work, and had to direct the balloon with the equivalent speed of a dial-up connection.

After 10 hours, small explosive charges cut the gondola from the balloon, allowing the instruments to return to Earth by parachute.

Knolker says the overall cost of the mission will be less than $100 million, with the bulk of that paying for the telescope. An equivalent space mission would cost 10 times as much, he estimates. Jonathan Grindlay, an astronomer at Harvard University in Cambridge, Massachusetts, says that balloon missions can cost even less — perhaps 5 per cent of a satellite mission — and still do good science.

Boomerang, a balloon released over the Antarctica in 1998, mapped the cosmic microwave background radiation and hinted that the Universe was ‘flat’ long before NASA’s arguably more famous — and more expensive — 2001 Wilkinson Microwave Anisotropy Probe mission. Of course, there are disadvantages to balloons.

Satellites can stay aloft collecting data for years, whereas high-altitude balloons rarely last more than a month. Eventually they leak, and come down. But balloons such as the one involved in the Sunrise project sometimes do not get the respect they deserve, Grindlay says.

“There’s been the feeling that balloons are a second class way of doing space experiments,” he says.

But Grindlay, who sits on a committee that NASA reconstituted in August to plan the next 5 to 10 years of balloon science, says NASA officials have recently “taken a much more enlightened view of balloon payloads.”

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