STEREO Ready to Take on the Sun
Artist's concept showing a coronal mass ejection (CME) sweeping past STEREO.
Credit: NASA

NASA could soon watch the Sun's violent behavior when the star's magnetic field becomes unstable shooting plasma and high-energy particles deep into space.

Almost identical twin probes, dubbed Solar TErrestrial RElations Observatory (STEREO) and scheduled to be launched aboard a Delta Rocket II on Aug. 31, will embark on a two-year mission to provide three dimensional views of the Sun.

The satellites will provide perspective on the origin, evolution and consequences of coronal mass ejections (CMEs).

CMEs are giant explosions on the Sun, caused by magnetic field lines annihilating one another, release a tremendous amount of energy. If directed the right way, ejected mass from CMEs can actually reach the Earth, explained Michael Kaiser, STEREO project scientist at NASA's Goddard Space Flight Center.

"Now we're very interested in this because these storms can cause all sorts of electrical disturbances on Earth particularly on spacecraft that are very sensitive to small changes in current and voltage levels," Kaiser said in a STEREO Pre-Launch Teleconference today. "They can also affect power on the ground."

A solar storm in the late 1980's was responsible for a famous outage of the entire Quebec power grid in Canada.

The energetic particles associated with such outbursts from the Sun can also harm astronauts when they leave the Earth's magnetic field to go into free space and on to long duration missions, such as a journey to Mars.

The data from the spacecraft will also help scientists determine how the Sun affects space weather.

"In terms of space-weather forecasting, we're where weather forecasters were in the 1950s," Kaiser said. "They didn't see hurricanes until the rain clouds were right above them. In our case, we can see storms leaving the Sun, but we have to make guesses and use models to figure out if and when they will impact Earth."

In order to create a multidimensional view of the Sun and provide depth perception, the two probes will be placed in different orbits of the Sun. Spacecraft "A" will be in orbit moving ahead of Earth and probe "B" will lag behind as the planet orbits the Sun. Each probe will sport imaging telescopes and equipment to measure solar wind particles and radio waves.