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Solar telescope rides balloon to fly over Earth

Posted: 05 Nov 2007 ?? ?Print Version ?Bookmark and Share

Keywords:solar telescope? balloon lift? Earth atmosphere?

With debris littering the space, a more sustainable way of launching payloads was inevitable. The latest approach uses a balloon to help lift a solar telescope above the Earth.

The U.S. National Center for Atmospheric Research (NCAR) recently launched its Sunrise vehicle on its maiden test flight to demonstrate its stability as a platform for the world's biggest solar telescope22 miles above the Earth with a 6,000lb, 1m-diameter mirror.

"Sunrise will give us the extremely fine observations we need to better understand the mechanisms behind magnetic fields on the Sun," said David Elmore, a NCAR research engineer. "We need to be able to predict the Sun's magnetic fields better, because they are blasted off into space from the Sun's corona and sometimes make it all the way to Earth where they affect our lives."

A balloon lifted NCAR's Sunrise solar telescope 22 miles above the Earth.

Solar flares house magnetic vortices as big as planets, shooting out magnetic disruptions that routinely reach Earth. Solar flares have been blamed for everything from disrupting communication to contributing to global warming. NASA has launched three solar observatories in recent years. The Stereo probe consists of twin satellites launched in different directions for snapping stereoscopic images; the third called Hinode carries a half-meter dish telescope.

NCAR's balloon, on the other hand, can launch a bigger payload: Sunrise will lift a 1m mirror plus a two-dimensional imaging magnetographic to map magnetic fields for a combined weight of over 6,000lbs.

Sunrise will fly above 98 percent of the Earth's atmosphere. At 120,000 feet (over 22 miles), air has just 2 percent of the density of sea-level pressure. The view from 22 miles reveals the curvature of the Earth and the deep black of space even during the day. Placing a telescope at that attitude places it above turbulence, dust, cloudsall the things that satellites are launched above, but at a cost of thousands of dollars compared to millions for a satellite launch.

Cheaper than satellite
"We realize many of the advantages of a satellite, but its a whole lot cheaper," said Elmore. "We get above the turbulence of the lower atmosphere, and we are above the ultraviolet-absorbing water vapor and ozone layer, which enables us to make very stable images of the sun using the very short UV wavelengths that never reach the ground."

The highest-resolution solar telescope in space, the half-meter mirror Hinode, is currently sending back stunning images of the Sun. Sunrises mirror will be twice as big, and will collect images at wavelengths twice as short (UV instead of visible light) yielding a total of four times the image resolution, according to NCAR. Sunrise will be able to resolve objects as small as 30km across (about 19 miles).

Hinode was launched by the Japanese Aerospace Exploration Agency in collaboration with NASA, the Particle Physics and Astronomy Research Council and the European Space Agency.

Researchers agree that they will get a closer look at the Sun with NCAR's telescope. "The scientists who are analyzing the Hinode observations can see indications of structures on the Sun that are too small to resolve," said Elmore.

Sunrise was launched on a 10hr test flight earlier this month from the Columbia Scientific Balloon Facility. Clear mages of the solar surface captured during the test flight convinced the team that their design could provide a stable platform for modern adaptive optics. After the test flight, the gondola carrying the telescope separated from the balloon and landed safely by parachute outside Dalhart, Texas.

The next test launch will be a multiday flight over the Arctic. Sunrise will fly from Sweden across the Atlantic Ocean, over Greenland, then land in Canada. When deployed, it will two-week missions before returning for maintenance.

NCAR collaborated on Sunrise with NASA, Germany's Max Planck Institute for Solar System Research, the Kiepenheuer Institute for Solar Physics, Spain's Astrophysics Institute of the Canary Islands and the Swedish Space Corp.

- R. Colin Johnson
EE Times

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