New Space Telescope to Target Sun Storms

While astronomers gaze at stars farther and farther out in the heavens, some scientists want to take a closer look at the star closest to us: the sun.

NASA plans to launch a new spacecraft, the Solar Dynamics Observatory (SDO), to take the most detailed observations ever of the sun to understand its complex weather and storms.

"The sun changes every time we look at it, [it] is never the same," said Dean Pesnell, SDO project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., in a Thursday briefing.

Scientists hope data from the new probe will help them understand changes in the sun's magnetic field, which gets more and less active on an 11-year cycle, sending out periodic flares of charged particles that can disrupt technology on Earth.

The $808 million spacecraft is slated to launch Feb. 9 at 10:36 a.m. EST (1536 GMT) atop an Atlas V rocket from Cape Canaveral, Fla.

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Published By SPACE.com
Article By Clara Moskowitz
SPACE.com Staff Writer
posted: 21 January 2010
05:19 pm ET

Register for the NASA SDO Goddard Tweetup

SDO is GO for Launch! Come to Goddard Space Flight Center in Greenbelt, Md., to watch the Solar Dynamics Observatory launch into space. Meet scientists and engineers, tour the cleanroom where SDO was built, and connect with common minds. Fifteen lucky Tweeps will be selected to join SDO scientists, engineers and invited guests at NASA's Kennedy Space Center in Florida to watch SDO ride a rocket into orbit and begin a new era in Heliophysics, the study of our sun and its effects on Earth and the solar system.

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Can a lull in solar activity head off climate change?

It might help but don't expect it to last, scientists say - the sun isn't the real issue



CAMBRIDGE - Old Sol these days is showing a strikingly bland face, one nearly unmarred by the usual wild magnetic storms, whipsawing coronal loops, and fiery plasma ejections

"The sun is in the pits of the deepest solar minimum in almost 100 years," said Madhulika Guhathakurta, lead program scientist for NASA's Living With A Star program, whose focus is solar variability and its effects on the earth.

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New Space Telescope to Watch the Sun

A new solar telescope, scheduled to launch this winter, will probe the sun's atmosphere and inner workings, helping scientists better understand how solar storms.

During its five-year mission, the Earth-orbiting Solar Dynamics Observatory (SDO) will seek to reveal how the sun's magnetic field works, what governs the ups and downs of the solar cycle and how solar activity affects Earth.

"The sun is a magnetic variable star that fluctuates on times scales ranging from a fraction of a second to billions of years," said Madhulika Guhathakurta, lead program scientist for the Living With a Star program (of which SDO is a part) at NASA Headquarters in Washington, D.C. "SDO will show us how variable the sun really is and reveal the underlying physics of solar variability."

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Solar Dynamics Observatory investigates the Sun's cycle of highs and lows

This is the first mission of NASA's Living With a Star program, which seeks to reveal how solar activity is generated and to understand the causes of solar variability and its impact on Earth.



How intense will the next solar cycle be? Can we predict when a violent solar storm will blast Earth with energetic particles? Could a prolonged period of inactivity on the Sun plunge Earth into a prolonged winter? These are a few of the questions that scientists anticipate the new Solar Dynamics Observatory (SDO) will help to answer.

Scheduled to launch this winter on an Atlas V rocket, SDO will peer into the Sun's atmosphere and probe the Sun's inner workings. SDO is the first mission of NASA's Living With a Star program, which seeks to reveal how solar activity is generated and to understand the causes of solar variability and its impact on Earth.

"Contrary to popular belief, the Sun is a magnetic variable star," Says Madhulika Guhathakurta, lead program scientist for Living With a Star at NASA Headquarters, Washington. "SDO will show us just how variable the Sun really is and will reveal the underlying physics of solar variability."

To accomplish the ambitious goals of the science team, "SDO will take full-disk, high-definition images of the Sun all of the time," says project manager Liz Citrin at NASA's Goddard Space Flight Center, Greenbelt, Maryland. Previous missions could not capture images at as rapid a cadence as SDO will, nor did they have the bandwidth to transmit all of the data back to Earth for processing. "These advances will provide the data to better understand how the Sun works and will allow us to develop the tools to predict its behavior."

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EVE: Measuring the Sun's Hidden Variability

Every 11 years, the sun undergoes a furious upheaval. Dark sunspots burst forth from beneath the sun's surface. Explosions as powerful as a billion atomic bombs spark intense flares of high-energy radiation. Clouds of gas big enough to swallow planets break away and billow into space. It's a flamboyant display of stellar power.

So why can't we see any of it?

Almost none of the drama of Solar Maximum is visible to the human eye. Look at the sun in the noontime sky and—ho-hum—it's the same old bland ball of light.

"The problem is, human eyes are tuned to the wrong wavelength," explains Tom Woods, a solar physicist at the University of Colorado in Boulder. "If you want to get a good look at solar activity, you need to look in the EUV."

EUV is short for "extreme ultraviolet," a high-energy form of ultraviolet radiation with wavelengths between 1 and 120 nanometers. EUV photons are much more energetic and dangerous than the ordinary UV rays that cause sunburns. Fortunately for humans, Earth's atmosphere blocks solar EUV; otherwise a day at the beach could be fatal.

When the sun is active, solar EUV emissions can rise and fall by factors of hundreds to thousands in just a matter of minutes. These surges heat Earth's upper atmosphere, puffing it up and increasing the air friction, or "drag," on satellites. EUV photons also break apart atoms and molecules, creating a layer of ions in the upper atmosphere that can severely disturb radio signals.

To monitor these energetic photons, NASA is going to launch a sensor named "EVE," short for EUV Variability Experiment, onboard the Solar Dynamics Observatory this winter.

"EVE gives us the highest time resolution and the highest spectral resolution that we've ever had for measuring the sun, and we'll have it 24/7," says Woods, the lead scientist for EVE. "This is a huge improvement over past missions."

Although EVE is designed to study solar activity, its first order of business is to study solar inactivity. SDO is going to launch during the deepest solar minimum in almost 100 years. Sunspots, flares and CMEs are at a low ebb. That's okay with Woods. He considers solar minimum just as interesting as solar maximum.

"Solar minimum is a quiet time when we can establish a baseline for evaluating long-term trends," he explains. "All stars are variable at some level, and the sun is no exception. We want to compare the sun's brightness now to its brightness during previous minima and ask: is the sun getting brighter or dimmer?"

The answer seems to be dimmer. Measurements by a variety of spacecraft indicate a 12-year lessening of the sun's "irradiance" by about 0.02% at visible wavelengths and 6% at EUV wavelengths. These results, which compare the solar minimum of 2008-09 to the previous minimum of 1996, are still very preliminary. EVE will improve confidence in the trend by pinning down the EUV spectrum with unprecedented accuracy.

The sun's variability and its potential for future changes are not fully understood—hence the need for EVE. "The EUV portion of the sun's spectrum is what changes most during a solar cycle," says Woods, "and that is the part of the spectrum we will be observing."

Woods gazes out his office window at the Colorado sun. It looks the same as usual. EVE, he knows, will have a different story to tell.

What Lies inside the Sun?

When a pond's surface is calm, you can see more clearly into its depths. As it turns out, the same is true for the sun.

Researchers are excited that the sun's surface is calmer now than it's been in almost a century. It's a rare opportunity — the first since the Space Age began — to peer more clearly into the sun's mysterious interior.

To take advantage of the opportunity, NASA is about to launch the Solar Dynamics Observatory (SDO). SDO is expected to launch this year, as early as November 2009.

"That's perfect timing," says Dean Pesnell, a solar physicist at the Goddard Space Flight Center in Greenbelt, Md. "The sun is experiencing a century-class solar minimum, offering the clearest possible views."

"SDO will actually see through the sun's surface," added Pesnell. "The process is a little like taking an ultrasound of a pregnant mother. You can see the baby right through the skin."

The sensor that performs this trick is called the Helioseismic and Magnetic Imager (HMI). It can sense acoustic waves moving through the sun, and turn those waves into a fairly clear image of the interior.

"There's a lot going on inside the sun that we don't understand," notes Todd Hoeksema, a solar physicist at Stanford University, Palo Alto, Calif. where the HMI was built. "The Solar Dynamics Observatory is bound to deliver some big discoveries."

The biggest discovery of all would be the inner workings of the solar dynamo. Deep beneath the sun's visible surface, massive currents of electrically-charged gas (plasma) circulate in patterns that give rise to the sun's powerful magnetic field. Almost all solar activity from sunspots to solar flares is regulated by this inner dynamo.

"Understanding how the dynamo works is a holy grail for stellar physics," says Pesnell. "It is the key to forecasting solar activity and space weather."

The problem is these deep flows are hidden from view. The sun's surface is bright and opaque, so it is impossible to look through it. Instead, solar physicists study the sun's interior the same way that geologists look deep into the Earth—via seismology. Just as earthquakes trigger seismic waves that travel through the Earth, shifting mass in the sun sends pressure waves rippling through its interior. These p modes (p for pressure) bounce around inside the sun, causing the star to ring like an enormous bell. HMI detects the surface vibrations, which in turn can be analyzed to reveal the depths.

Sunspots can get in the way of the waves, distorting their times and frequencies, making it tricky to figure out what's really happening inside the complicated solar interior. That's why the current lack of sunspots is good for helioseismology.

"You have more sensitivity to what's happening deep in the sun when there's not as much interference from the surface," Hoeksema explains. At the peak of the solar cycle, sunspots are numerous. So far in 2009, the sun's surface has been free of sunspots about 80 percent of the time — the most tranquil it's been since 1913.

From a geosynchronous orbit 22,000 miles above Earth's surface, SDO will observe helioseismic waves more precisely than ever before. The current gold standard for observing the sun is a satellite called the Solar and Heliospheric Observatory, or SOHO, which maps helioseismic activity with mega-pixel resolution once every minute or so. HMI will up the ante to 16 megapixels every 45 seconds, resulting in a far more detailed view of the solar interior.

SDO will also improve on SOHO by beaming its torrent of raw data down to Earth unprocessed. Because of limited download bandwidth, SOHO performs some calculations while the data are still onboard the spacecraft. Only the results are beamed to scientists. Since SOHO was launched in 1995, scientists have since devised better ways to process the data and correct for errors. But there's no way they can apply these new techniques to SOHO imagery because the data have already been "crunched" by the time they leave the spacecraft.

To give scientists full access to its original data, SDO will have a continuous, 150 megabit per second download link. In comparison, most home high-speed internet connections are only 1 to 10 megabits per second.

Somewhere in all those p modes will be the telltale signs of solar jet streams, subsurface winds, proto-sunspots, and the solar dynamo itself — all "seen" with unprecedented clarity.

With the sun so calm, now is a great time to look.