PROBA-3
[1]PROBA-3 is the third satellite 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.[2]Curently proba-3 is in its preparatory study phase.[3] 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 stabelized 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 observations 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.[4]
the primary mission of proba-3 is solar coronagraph by ussing the telescope on the larger of the two satelites to view the suns corona and other craft is manoeuvred to accurately occult the main disc of the Sun. [5]