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New US Spacecraft to Offer Better Warning of Solar Outbursts


The United States has launched two more satellites to peer at the sun and help scientists better predict when solar storms might disrupt Earth's electrical systems. The twin orbiters will provide the first three-dimensional view of these gigantic solar blasts.

Scientists once thought the space between Earth and Sun was a vacuum. But we now know that the sun fills the void with gusts of hot, electrically charged atomic particles called the solar wind. Sometimes this wind blows hard.

When the sun's outer layer, the corona, is very active, it hurls nearly one-third of its gaseous matter outward at supersonic speeds. Sometimes these so-called coronal mass ejections are aimed at Earth.

Solar scientist Michael Kaiser at the U.S. space agency NASA says a heavy blast can produce a shock wave that compresses Earth's magnetic field. This can cause some lovely atmospheric colors, but otherwise wreaks havoc. "These particles can cause the northern lights, but they can also cause electrical damage to spacecraft that are in orbit or even to ground power systems and conceivably even astronauts. If they were exposed to radiation from one of these storms, they could be harmed," he said.

Early detection of these solar charged-particle clouds is one of the goals of U.S., European, and Japanese solar observation satellites now in orbit.

This detection allows government alerts to go out for operators to take protective measures with electrical grids, satellites, and astronauts. But the warning time is only about 12 hours, even though coronal mass ejections take three or four days to travel to Earth.

This is because the present satellites operate in the line of site between the sun and Earth and cannot easily detect whether a charged particle cloud is heading directly toward us or will move past Earth with no impact.

Two new U.S. spacecraft launched by NASA on one rocket Wednesday should end this uncertainty and lengthen warning time by providing a stereoscopic view of coronal mass ejections. The craft, named STEREO, are heading in opposite directions and after 90 days of orbit adjustment, they will observe solar-particle travel from both sides of their path instead of head on.

Michael Kaiser say the STEREO satellites' 500-thousand kilometer separation will provide depth perception, just as our eyes do by being separated in our heads. "We are going to put two spacecraft off to the sides and triangulate in three dimensions to look at these coronal mass ejections. We are hoping that way we will be able to get a much better prediction of when they are going to arrive at Earth and the exact direction they are moving," he said.

The spacecraft will do this from a unique pair of orbits. One will circle the sun ahead of Earth while the other one will do so trailing Earth.

"We are at the dawning of a new age of solar observations. We are going to be viewing things in a new dimension for us," said Russell Howard, a U.S. Naval Research Laboratory scientist who will help analyze the STEREO data. "We are going to be able to observe mass ejections, coronal mass ejections, from their origin at the sun all the way to Earth. This will be the first time we have ever seen that. It will be truly remarkable," he said.

At NASA headquarters, solar scientist Madhulika Guhathakurta says the STEREO mission is part of the space agency's effort to improve understanding of the physics of the sun and its interaction with the planets through its coronal explosions. "This is going to be significant in terms of providing a breakthrough of our understanding of not only coronal mass ejections, but [also] the ambient sun, the solar corona, and the interplanetary medium as a whole. I think this is going to forever change our view of the sun," he said.

The STEREO mission is designed to last two years.