Wednesday, February 10, 2010

CAPE CANAVERAL — Like a local meteorologist, a NASA satellite set to launch this morning from Cape Canaveral Air Force Station hopes to deliver the solar system's weather report.

Its goal is a better understanding of the sun, whose shifting magnetism and roiling surface can threaten Earth's satellites, power grids and communications systems.

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"Understanding solar variability is crucial to our modern way of life, which depends on it," said Madhulika Guhathakurta, a program scientist for NASA's Solar Dynamics Observatory mission.

A snapshot every 10 seconds

A 19-story United Launch Alliance Atlas V rocket carrying the satellite is scheduled to blast off at 10:26 a.m., weather permitting.

The spacecraft — nearly 15 feet tall and weighing more than 3 tons — is the first mission of NASA's Living with a Star program established in 2001. Over at least five years, the $850 million mission promises to provide the most detailed look yet at the sun, inside and out.

Three sets of instruments will take high-resolution pictures every 10 seconds, record ultrasound-like views of the sun's interior and measure the intensity of extreme ultraviolet rays that would be fatal if not deflected by the Earth's upper atmosphere.

The sun was once commonly regarded as a pale, yellow ball that changed little over time, but scientists now call it a "variable" star, albeit an ordinary one.

"The sun is really not a constant," Guhathakurta said. "Modern telescopes and spacecraft have really penetrated the blinding glare of the sun and have found sort of a maelstrom of unpredictable turmoil."

That turmoil ebbs and flows in cycles averaging 11 years when the sun's magnetic field reverses direction.

Recently, the sun has been in an extended quiet period, generating few sunspots and related weather events that have surprised scientists. As solar activity increases, so do the solar flares and powerful explosions that can wreak havoc on high-tech systems.

'Holy Grail' of solar physics

The storms can disrupt Global Positioning System navigation and emergency radio communication. They can damage satellites by increasing the atmospheric drag on them, and the intense radiation could be harmful to astronauts traveling to the moon or Mars.

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Understanding the processes behind the sun's magnetic activity and the timing of its cycles is the "Holy Grail" of solar physics, Guhathakurta said.

Better forecasts of solar events would give technology operators time to take pre-emptive steps, such as adjusting power transmission lines to prevent cascading failures. "This is a case where you can take action on the basis of knowledge," said Richard Fisher, Heliophysics division director at NASA headquarters in Washington, D.C. "If you have knowledge that such a thing is likely, you can adjust the power systems to avoid difficulties."

Dean reports for Florida Today

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A swarm of "smart dust" spacecraft, positioned at a sweet spot between the Earth and the sun, could alert us to the approach of dangerous space storms well before a conventional craft can. The first prototypes are due for launch into low-Earth orbit this year, perhaps as early as May. Mason Peck, a mechanical engineer at Cornell University in Ithaca, New York, and his colleague Justin Atchison have designed a 1-centimetre-square spacecraft that is 25 micrometres thick and weighs under 7.5 milligrams. The craft is modelled on the dust particles that orbit the sun and are propelled by the photons streaming out from the sun. This solar radiation pressure would have a negligible effect on normal-sized spacecraft but is significant at the millimetre scale. The grooved edges of the "spacecraft-on-a chip" deflect incoming photons in such a way as to ensure it always faces the sun. The craft's miniature size would let it hitch a ride into space on the back of another satellite mission headed for the Lagrange point between the Earth and the sun. A Lagrange point is a kind of gravitational sweet spot, where a small object can be stationary relative to two larger objects.

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