The sun in another dimension

Twin spacecraft capture images for scientists to examine in 3-D

April 24, 2007|By Frank D. Roylance | Frank D. Roylance,Sun reporter

GREENBELT -- Scientists with NASA's "Stereo" mission have gotten their first look at the sun in three dimensions - a revelation that could mean more accurate forecasts of the solar storms that rattle power grids and blind the satellites vital to modern communications, navigation and weather forecasting.

The revolutionary new view of the sun comes from two Maryland-built spacecraft launched last October and controlled from the campus of the Johns Hopkins University's Applied Physics Lab near Laurel.

By late last month they were far enough apart to provide the first-ever stereoscopic view of the sun. That had some of the nation's top solar scientists donning goofy-looking 3-D spectacles yesterday to have a look at the new stills and movies - just back from orbit.

They reveal the sun not as a flat disk, but as a seething, shimmering orb. Through red-and-blue 3-D glasses, it looks like a ball you can reach out and grab - if you dare.

Web surfers can view some of the spectacular images on the Internet. Even better photos are being shown, in high-definition digital color, by museums and planetariums around the world.

The Maryland Science Center is showing the movies in standard definition, with red/blue cardboard glasses.

"We've got the stereo stuff going in the SpaceLink Gallery," said Jim O'Leary, director of the center's Davis Planetarium. "We've got the 3-D glasses. ... It's pretty spectacular, We've gotten a lot of `Wows' from our visitors."

That was an almost universal response when scientists saw the first payback from their $520 million international mission, which some have been working on for a decade.

"The first reaction was, `Great! The instruments work,'" said Stereo co-investigator Simon Plunkett, of the Naval Research laboratory. "Beyond that, the first reaction was, `Wow!'"

Solar physicists have long observed the sun and its flares, storms and coronal mass ejections - but only in two dimensions.

Deciphering their true shape and plotting their development - without the depth perception our eyes provide by viewing an object from slightly different angles - was like trying to catch a fly ball with one eye closed.

Now, Plunkett said, "To sit there and actually follow a sequence and follow it in 3-D, it's really amazing. ... We had some very loud cheers when we first saw these images."

Scientists say today's space-weather forecasting is about where hurricane forecasting was in the 1950s, before satellite imagery and computer modeling.

With Stereo, they will correct and fine-tune the computer models they use to predict the speed, direction and strength of unfolding solar storms as they sweep across the void toward Earth.

Data derived from a two-dimensional image can be interpreted several ways by existing computer models, they said. The extra dimension will make them more reliable.

"One of the things we want to be able to understand is what the strength of the sun's magnetic field is. We need to view it in 3-D to get that," said Plunkett. "Without it, it's difficult to predict when an eruption is going to happen."

With better models, space-weather forecasters hope they'll be able to provide better protection for the planet's power grids and communications satellites - as well as the health of future astronauts on their way to the moon and Mars.

A 1989 solar storm disrupted utilities in six states and burned out a $10 million transformer in New Jersey. A related power outage in Quebec threw 6 million people into the dark.

Communications satellites had to be repointed, weather satellites lost data and some went out of control for hours.

"If we could tell NOAA [the National Oceanic and Atmospheric Administration] there was a 60 percent probability of a dangerous event, that would be very helpful," Plunkett said.

The two Stereo (for Solar Terrestrial Relations Observatory) spacecraft were built by the Applied Physics Laboratory and launched in October aboard a single rocket from Cape Canaveral, Fla.

Scientists manage daily operations from a control center on the APL campus.

From an initial orbit around Earth and the moon, controllers used the moon's gravity to fling the spacecraft into different orbits around the sun. One now flies just ahead of Earth and a bit faster, while the other falls behind.

As the distance between the two spacecraft has increased since December, the stereoscopic view available for scientists has steadily improved. When the angle between the pair reached 4 degrees last month, mission managers began recording still images. They spliced the photos into short 3-D movies spanning 10 days, from March 17 to 27.

By next January, the separation will be even better, about 45 degrees. By the time current funding for the mission ends in two years, the craft will be separated by almost 90 degrees, and their value for stero imaging will diminish.

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