Getting a satellite ready to be launched involves a long list of jobs, but with the Copernicus Sentinel-3B satellite now fuelled, this particular 'to do' list is significantly shorter. And, importantly, all is on track for lift-off on 25 April.

Since hydrazine is extremely toxic, only specialists dressed in bulky astronaut-like suits remained in the cleanroom for the duration of the activity. A doctor, fire personnel and security staff waited nearby with an ambulance and fire engine ready to respond to any problems.

ESA's Sentinel-3 project manager, Bruno Berruti, said, "This is a big job ticked off our list, and thanks to the expertise of the Thales Alenia Space propulsion team, it was executed perfectly."