• Launch date : 26 October 2006
• Agency : NASA
STEREO (Solar TErrestrial RElations Observatory) is the third mission in NASA’s Solar Terrestrial Probes program (STP). This two-year mission will provide a unique and revolutionary view of the Sun-Earth System. The two nearly identical observatories – one ahead of Earth in its orbit, the other trailing behind – will trace the flow of energy and matter from the Sun to Earth as well as reveal the 3D structure of coronal mass ejections and help us understand why they happen. STEREO will also provide alerts for Earth-directed solar ejections, from its unique side-viewing perspective adding it to the fleet of Space Weather detection satellites.
STEREO, launched on Oct. 25, 2006, consists of observation systems orbiting the Sun in front of and behind the Earth. Just as our two eyes give us a three-dimensional view of the world, the views provided by each STEREO system can be combined to provide a three-dimensional view of the Sun. Though the first STEREO images were taken in early December, the two systems started to give three-dimensional images of our Sun in April 2007.