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Last Updated: Monday, 18 December 2006, 11:39 GMT
Solar storm disrupts spacecraft
The Sun   Image: Esa/Nasa
Soho took an image of the solar flare
An energetic storm which erupted on the Sun has caused disruption to satellites and may have caused a glitch on the International Space Station (ISS).

The solar flare interrupted signals in space and forced mission controllers to shut systems down to avoid damage to spacecraft orbiting Earth.

The flare set off a fast-moving stream of atomic particles towards Earth.

It may also have caused a fault in the system controlling the space station's orientation in space.

The ISS usually relies on four large gyroscopes that spin to control its "attitude" without consuming copious amounts of propellant.

Space station flight director Joel Montalbano told reporters in Houston, US, that the unusual solar activity had caused the density of Earth's atmosphere to increase.

"We're seeing some problems with our software converging on a nice stable attitude for attitude control," Space.com quoted him as saying.

Taking refuge

Last week, astronauts were forced to sleep in protective areas of the station and shuttle as a precaution against the storm.

The Soho (Solar & Heliospheric Observatory) spacecraft took an image of a large solar flare on 13 December that led to the energetic solar radiation storm.

Several European Space Agency (Esa) missions, including Integral, Cluster and Envisat, felt the storm's effects.

Parts of one Cluster satellite lost power, and an instrument on another shut itself down after the burst of solar energy, the agency said.

The Cluster mission comprises four separate satellites which are designed to study the perpetual stream of subatomic particles given out by the Sun.

"When you have a burst, the flux of very fast charged particles increases dramatically. This can cause discharges in electronic components - the so-called 'single-event upsets' - on the spacecraft, as well as damage or loss of data in solid-state memories," said Juergen Volpp, operations manager on the Cluster mission.

Instruments on Envisat, a satellite that monitors the Earth's land, atmosphere, oceans and ice caps, shut down, and mission managers for another craft had to protect its instruments, Esa said.

On 14 December, China's People's Daily reported widespread disruption of shortwave radio communications in China.

Particles discharged by solar storms can disrupt telephone systems, broadcast signals, and navigation networks.

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