The Solar and Heliospheric Observatory, or SOHO, reached a milestone on Dec. 2, 2013: It turned 18. SOHO was launched on Dec. 2, 1995, and in terms of normal spacecraft operational years that would be tantamount to several lifetimes.

SOHO, a joint mission of the European Space Agency and NASA, has been a dependable solar watchdog all the while. More than 4,600 scientific papers using data from SOHO have appeared in the refereed literature. SOHO has also discovered more than 2,500 comets, something no one anticipated before launch. Over the 2013 Thanksgiving holiday, SOHO played a crucial role in tracking Comet ISON. Though some of its instruments are no longer in operation, it still plays a unique role in monitoring solar and heliospheric activity.

Congratulations to all who have been involved in making this mission such a resounding success!

Image courtesy Steele Hill