Spacecraft to monitor sun

Nasa has launched twin spacecraft that will send back the first three-dimensional views of the sun and study violent solar storms over its two-year mission.

The US space agency said it had launched its Solar Terrestrial Relations Observatories mission, or Stereo, late on Wednesday from Cape Canaveral, Florida.

The two golf-cart-sized probes will swing by the moon and then head off on separate orbits around the sun.

Just as humans use their two eyes for depth perception, the differing images recorded by the two craft will allow astronomers to piece together three-dimensional views of the sun.

The probes will collect data on the violent solar storms, known as coronal mass ejections, that can disrupt satellites, radio communications and electric power grids on earth.

Such storms also can cause particularly strong aurora, the nighttime displays known as the northern lights and the southern lights.

The mission will help people who design satellites and other space-based technology minimize disruptions caused by these solar storms, said a Nasa scientist said in a prepared statement.

"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," said Michael Kaiser, a Stereo project scientist at the Goddard Space Flight Centre in Greenbelt, Maryland.