About the STEREO Mission

STEREO (Solar TErrestrial RElations Observatory) was launched in 2006, employing two nearly identical space-based observatories - one ahead of Earth in its orbit, the other trailing behind - to provide the first-ever stereoscopic measurements to study the Sun and the nature of its coronal mass ejections, or CMEs. The STEREO Behind spacecraft was lost in 2014, but the STEREO Ahead spacecraft continues to operate and make important science observations of the Sun.

STEREO's scientific objectives are to:

• Understand the causes and mechanisms of coronal mass ejection (CME) initiation.
• Characterize the propagation of CMEs through the heliosphere.
• Discover the mechanisms and sites of energetic particle acceleration in the low corona and the interplanetary medium.
• Improve the determination of the structure of the ambient solar wind.

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• Why STEREO?
• Mission Concept
• Mission Design
• STEREO 10 Year Anniversary
• Report of the Science Definition Team for the Stereo Mission (1.8MB PDF)