PROBA-3 is the third satellite mission in the European Space Agency's series of PROBA low-cost satellites that are being used to validate new spacecraft technologies while also carrying scientific instruments. Currently PROBA-3 is in its preparatory study phase. PROBA-3 will show the technology that is required for formation flying of two or more spacecraft.
PROBA-3 will be composed of two independent, three-axis stabilized spacecraft flying close to one another with the ability to accurately control the attitude and separation of the two craft. The spacecraft pair will fly a highly elliptical orbit divided between periods of accurate formation flying, when payload operations will be possible, and periods of free flight. The length of the formation control period will be the result of a trade-off involving the amount of fuel needed to maintain the orbits when in formation.
The primary mission of PROBA-3 is solar coronagraphy by using the telescope on the larger of the two satellites to view the sun's corona while the other spacecraft is maneuvered to accurately occult the disc of the sun.
Currently, PROBA-3 is scheduled to be launched in 2017.The mission is planned to have a lifetime of around two years.