Acting on a suggestion of the European Commission, ESA invited independent signal-receivers from all over the world to submit a proof of their fixes
The invitation was open to any kind of public : private researcher, satellite hobbyists, SME's, universities, etc ...
The proofs sent were evaluated by ESA/ESTEC's technical services, and a QSL certificate was awarded to the 50 first candidates.
The success of the initiative actuelly exceeded the expectations, with submissions sent from all over the globe.
A QSL card is a written confirmation of either a two-way radiocommunication between two amateur radio stations or a one-way reception of a signal from an AM radio, FM radio, television or shortwave broadcasting station. It can also confirm the reception of a two-way radiocommunication by a third party listener (Wikipedia).