NASA Stereo satellites over Earth, computer artwork. One satellite will orbit the Sun just ahead of the Earth, with the other orbiting just behind the Earth. Images of the Sun taken by both satellites will be combined to form three dimensional images of the Sun. The mission will study coronal mass ejections (CMEs), solar storms that cause violent eruptions from the Sun's surface that travel outwards at hundreds of kilometres per second. CMEs can damage electrical equipment aboard satellites and spacecraft and cause powerful magnetic storms in the Earth's atmosphere that disrupt power supplies and communications. The satellites were launched on 27 October 2006.