Artist view of the ROCKOT launcher with its fairing removed to show the main SMOS satellite, and below it, the smaller Proba-2 satellite inside the double adapter.

Proba stands for PRoject for OnBoard Autonomy. The Proba satellites are among the smallest spacecraft ever to be flown by ESA, but they are making a big impact in the field of space technology. Proba-2 is the second of the series, building on nearly eight years of successful Proba-1 experience.