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Solar satellite launched to study space weather

A new NASA satellite will study the physics of the sun and the titanic magnetic storms, flares, and explosions that drive space weather across the solar system.

An Atlas 5 rocket boosted NASA's Solar Dynamics Observatory into orbit Thursday, kicking off an $850 million mission to study the physics of the sun and the titanic magnetic storms, flares, and explosions that drive space weather across the solar system.

Using three sophisticated instruments that will collect enormous amounts of data over short time scales, scientists hope to improve their ability to predict the onset of major flares and other phenomena that can disrupt communications, satellite navigation, and power grids.

An Atlas 5 rocket carrying NASA's Solar Dynamics Observatory satellite blasts off from the Cape Canaveral Air Force Station. Pat Corkery/United Launch Alliance

"SDO will observe the sun almost continuously for more than five years, sending back data at an astounding rate of 1.5 terabytes per day," said Project Manager Elizabeth Citrin at NASA's Goddard Space Flight Center. "That's almost 500,000 music downloads per day.

"With this wealth of data, we will learn how solar activity is created and how it will affect space weather. And space weather is what affects us humans here on Earth, our satellites, communications, power grids."

Madhulika Guhathakurta, lead scientist with NASA's Living with a Star program, said modern society's increasing dependence on satellite communications means "that any variability caused by the sun has an impact."

"Solar variability can affect human spaceflight, satellite operations, smart power grids, GPS navigation, emergency radio communications, air travel, financial services," she said.

SDO "will observe the sun faster, deeper and in greater detail than any previous observatories," she said, "breaking barriers of space, time and clarity that have long blocked progress in solar physics."

Running one day late because of high winds at the Cape Canaveral Air Force Station in Florida, the United Launch Alliance Atlas 5 rocket blasted off at 10:23 a.m. EST.

After a smooth climb out of the atmosphere, the rocket's Centaur second stage propelled the 8,800-pound solar-powered satellite toward geosynchronous orbit 22,300 miles up.

It will take the spacecraft about three weeks to reach its final parking slot above a ground station in New Mexico, where two 60-foot dish antennas were built to take in the torrent of data from SDO's instruments--the equivalent of 300 movie downloads per day.

SDO builds on the successes of the Solar and Heliospheric Observatory, a joint project between the European Space Agency and NASA, and a fleet of more modest satellites that have revolutionized solar physics in recent years.

An artist's concept of the Solar Dynamics Observatory in orbit. NASA

But the difference between SDO's output and previous sun-study satellites is a bit like the difference between a movie and a cartoon flip book.

"SDO is the crown jewel of a fleet of NASA satellites that are designed to study the sun," said Michael Luther, deputy associate administrator for programs. "SDO is the most advanced spacecraft of its type ever designed and flown. It will give higher quality, more comprehensive, and faster data rate than any spacecraft of its kind before."

One of its instruments, the Atmospheric Imaging Assembly, will snap multi-wavelength full-disk images of the sun every three quarters of a second. It will study on the sun's corona--the origin of the solar wind, flares, and coronal mass ejections--taking 4096-by-4096 pixel pictures spanning 1.3 solar diameters.

"On the Earth, we have these things called earthquakes," said Principal Investigator Alan Title. "Earthquakes occur on tectonic plates. That's where big masses of the Earth move across each other and create shears, and these plates break and release a lot of energy. On the sun, the magnetic fields are the logical equivalent of tectonic plates. And as they move and create shear, they have the potential of releasing huge amounts of energy."

The Atmospheric Imaging Assembly was built to "develop real physical understanding of what goes on so we can make more sophisticated predictions of what's happening."

The Extreme Ultraviolet Variability Experiment will monitor changes in the sun's ultraviolet output, a critical factor in how the sun heats and energizes Earth's upper atmosphere. Changes in ultraviolet radiation can cause Earth's atmosphere to swell slightly, increasing drag on satellites in low-Earth orbit and triggering changes that reduce the accuracy of satellite navigation signals.

SDO's third instrument, the Helioseismic and Magnetic Imager, will measure magnetic fields at the sun's surface. It also will look into the star's interior by monitoring low-frequency sound waves, generated by convection, that cause the surface to pulsate, moving up and down several hundred yards every few hours.

By analyzing the vibrations at the surface, researchers can infer details about the sun's interior.

"The variability of the sun is predominantly caused by magnetic fields," said Principal Investigator Phil Scherrer. "So if we want to be able to predict that variability, we have to start with predicting the magnetic fields."

If all goes well, full-time science operations will begin in about two months, after the satellite is maneuvered into its final orbit and its instruments are checked out and calibrated.