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  NASA's STEREO solar observatories

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Author Topic:   NASA's STEREO solar observatories
Robert Pearlman
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Posts: 27328
From: Houston, TX
Registered: Nov 1999

posted 10-25-2006 09:23 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA's twin Solar Terrestrial Relations Observatories mission, known as STEREO, successfully launched Wednesday at 8:52 p.m. EDT from Cape Canaveral Air Force Station, Fla.

STEREO's nearly identical twin, golf cart-sized spacecraft will make observations to help researchers construct the first-ever three-dimensional views of the sun. The images will show the star's stormy environment and its effects on the inner solar system, vital data for understanding how the sun creates space weather.

"The stunning solar views the two observatories will send back to Earth will help scientists get a better understanding of the sun and its activity than we've ever been able to obtain from the ground or any of our other missions," said Nick Chrissotimos, STEREO project manager at NASA's Goddard Space Flight Center, Greenbelt, Md.

The two observatories were launched on a Delta II rocket in a stacked configuration and separated from the launch vehicle approximately 25 minutes after lift-off. After receiving the first signal from the spacecraft approximately 63 minutes after launch, mission control personnel at the Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Md., confirmed each observatory's solar arrays successfully deployed and were providing power. NASA's Deep Space Network antennas in Canberra, Australia received the initial radio signals.

During the next two weeks, mission managers at APL will ensure all systems are properly working. For the next three months, the observatories will fly from a point close to Earth to one that extends just beyond the moon's orbit.

After about two months, STEREO's orbits will be synchronized to encounter the moon. The "A" observatory will use the moon's gravity to redirect it to an orbit "ahead" of Earth. The "B" observatory will encounter the moon again for a second swing-by about one month later to redirect its position "behind" Earth. STEREO is the first NASA mission to use separate lunar swing-bys to place two observatories into vastly different orbits around the sun.

Just as the slight offset between human eyes provides depth perception, this placement will allow the STEREO observatories to obtain 3-D images of the sun. The arrangement also allows the two spacecraft to take local particle and magnetic field measurements of the solar wind as it flows by.

During the observatories' two-year mission, they will explore the origin, evolution and interplanetary consequences of coronal mass ejections, some of the most violent explosions in our solar system. These billion-ton eruptions can produce spectacular aurora, disrupt satellites, radio communications and Earth's power systems. Energetic particles associated with these solar eruptions permeate the entire solar system and can be hazardous to spacecraft and astronauts.

Better prediction of solar eruptions provides more warning time for satellite and power grid operators to put their assets into a safe mode to weather the storm. A better understanding of the nature of these events will help engineers build better and more resilient systems.

"We're becoming more and more reliant on space technologies in our everyday lives and are hatching ambitious plans to explore our outer space surroundings," said Michael Kaiser, STEREO Project Scientist at Goddard. "But nature has a mind of its own and STEREO is going to help us figure out how to avoid those surprises the sun tends to throw at us and our best-laid plans."

Goddard manages the STEREO mission. The APL designed and built the spacecraft. The laboratory will maintain command and control of the observatories throughout the mission, while NASA tracks and receives the data, determines the orbit of the satellites, and coordinates the science results. Each observatory has 16 instruments, including imaging telescopes and equipment to measure solar wind particles and to perform radio astronomy.

The STEREO mission includes significant international cooperation with European partners in instrument development, data sharing and analysis.

Robert Pearlman
Editor

Posts: 27328
From: Houston, TX
Registered: Nov 1999

posted 02-06-2011 11:52 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA release
First Ever STEREO Images of the Entire Sun

It's official: The sun is a sphere.

On Feb. 6th, NASA's twin STEREO probes moved into position on opposite sides of the sun, and they are now beaming back uninterrupted images of the entire star -- front and back.

"For the first time ever, we can watch solar activity in its full 3-dimensional glory," says Angelos Vourlidas, a member of the STEREO science team at the Naval Research Lab in Washington, DC.

NASA released a 'first light' 3D movie on, naturally, Super Bowl Sunday:


"This is a big moment in solar physics," says Vourlidas. "STEREO has revealed the sun as it really is -- a sphere of hot plasma and intricately woven magnetic fields."

Each STEREO probe photographs half of the star and beams the images to Earth. Researchers combine the two views to create a sphere. These aren't just regular pictures, however. STEREO's telescopes are tuned to four wavelengths of extreme ultraviolet radiation selected to trace key aspects of solar activity such as flares, tsunamis and magnetic filaments. Nothing escapes their attention.

"With data like these, we can fly around the sun to see what's happening over the horizon -- without ever leaving our desks," says STEREO program scientist Lika Guhathakurta at NASA headquarters. "I expect great advances in theoretical solar physics and space weather forecasting."

Consider the following: In the past, an active sunspot could emerge on the far side of the sun completely hidden from Earth. Then, the sun's rotation could turn that region toward our planet, spitting flares and clouds of plasma, with little warning.

"Not anymore," says Bill Murtagh, a senior forecaster at NOAA's Space Weather Prediction Center in Boulder, Colorado. "Farside active regions can no longer take us by surprise. Thanks to STEREO, we know they're coming."

NOAA is already using 3D STEREO models of CMEs (billion-ton clouds of plasma ejected by the sun) to improve space weather forecasts for airlines, power companies, satellite operators, and other customers. The full sun view should improve those forecasts even more.

The forecasting benefits aren't limited to Earth.

"With this nice global model, we can now track solar storms heading toward other planets, too," points out Guhathakurta. "This is important for NASA missions to Mercury, Mars, asteroids... you name it."

NASA has been building toward this moment since Oct. 2006 when the STEREO probes left Earth, split up, and headed for positions on opposite sides of the sun (movie). Feb. 6, 2011, was the date of "opposition" -- i.e., when STEREO-A and -B were 180 degrees apart, each looking down on a different hemisphere. NASA's Earth-orbiting Solar Dynamics Observatory is also monitoring the sun 24/7. Working together, the STEREO-SDO fleet should be able to image the entire globe for the next 8 years.

The new view could reveal connections previously overlooked. For instance, researchers have long suspected that solar activity can "go global," with eruptions on opposite sides of the sun triggering and feeding off of one another. Now they can actually study the phenomenon. The Great Eruption of August 2010 engulfed about 2/3rd of the stellar surface with dozens of mutually interacting flares, shock waves, and reverberating filaments. Much of the action was hidden from Earth, but plainly visible to the STEREO-SDO fleet.

"There are many fundamental puzzles underlying solar activity," says Vourlidas. "By monitoring the whole sun, we can find missing pieces."

Researchers say these first-look whole sun images are just a hint of what's to come. Movies with even higher resolution and more action will be released in the days and weeks ahead as more data are processed. Stay tuned!

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