July 14, 2010

Solar Eruption Was Potential Cause Of Zombie Satellite

Scientists now say that a massive eruption from the sun in April might have caused the Galaxy 15 satellite to become a "zombie."

According to the U.S. Naval Research Laboratory (NRL), the explosion of plasma and magnetic energy occurred on April 3 and was observed by NASA's sun-watching STEREO spacecraft.  The NRL released new images of the solar storm last week.

NRL officials said that the storm appears to have disabled Intelsat's Galaxy 15 communications satellite.  The zombie satellite lost contact with its ground controllers on April 5 and has been drifting around Earth ever since.

Solar storms are a known risk to satellites.  The charged particles in a storm can short out electrical equipment.

The observations suggest that the explosion, which is called a coronal mass ejection (CME), flung material away from the sun at 627 miles per second.  The CME was moving at 2.2 million mph while it was still close to the sun on April 3.  It slowed down to about 1.5 million mph when it reached Earth on April 5.

While the satellite stopped communicating with the ground control center, its C-band telecommunications payload is stuck on, earning it the nickname "zombie satellite" because of its ability to interfere with other working satellites.

"Coronal mass ejections, or CMEs, are powerful eruptions of plasma and magnetic energy from the sun's outer atmosphere, or corona," NRL officials wrote in the July 7 statement. "When these sudden outbursts are directed toward Earth, they can have both breathtakingly beautiful and potentially damaging effects."

The study of the explosion was performed using NASA's Solar Terrestrial Relations Observatory (STEREO), a set of twin spacecraft on opposite sides of Earth that continuously watch the sun in what produces a stereo view, due to the wide separate of the probes in space.

Russel Howard, the STEREO mission's principal investigator at the NRL, said that the unique lateral views provided by STEREO were ideal for studying the kinematics and morphology of the developing event.

Three-dimensional reconstruction of the evolving cloud of electrified gas showed its form to be a crescent-shaped "flux rope" with a shock wave driven in front.

Prior awareness that the CME was headed straight for Earth came from the NRL-developed coronagraph aboard the SOHO solar observatory.  NRL officials said that Large Angle Coronograph-Spectrograph (LASCO) instrument on SOHO observed a "halo" around the sun that was formed by the expanding and approaching solar eruption.

Meanwhile, the zombie satellite has forced other communication satellites to conduct evasive maneuvers from time to time to avoid signal interference.  However, Intelsat officials said the chances of Galaxy 15 hitting another satellite are so remote that they are almost non-existent.


Image Caption: The STEREO (Ahead) spacecraft caught this spectacular eruptive prominence in extreme UV light as it blasted away from the Sun (Apr. 12-13, 2010). This was certainly among the largest prominence eruptions seen by either the STEREO or SOHO missions. The length of the prominence appears to stretch almost halfway across the sun, about 500,000 miles. Prominences are cooler clouds of plasma that hover above the Sun's surface, tethered by magnetic forces. They are notoriously unstable and commonly erupt as this one did in a dramatic fashion.


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