The team at ATV-CC emailed earlier to confirm that today’s Refuelling System (RFS) check went well. ESA’s Mission Director Mike Steinkopf wrote:

This morning we had the RFS leak check in anticipation of the ISS refuelling planned for mid-May. The leak check is a prerequisite for the actual propellant transfer. The leak check included verification that there was no leakage in the fuel lines interconnecting ATV with the ISS. The connection was established during the night from 02:00 CET to 09:00 CET; the leak check itself ran about 5 hours. The results showed a ‘nominal’ status, with no leakage detected.

ATV Johannes Kepler is carrying about 850.6 l of fuel for the ISS. Mike added that controllers at MCC-M confirmed that ATV is ready for the actual propellant support (= refuelling the Station).