The operator stays close to the control panel, waiting for the order to turn a valve. One of the first steps (which is just being completed) is to flush the lines. Once this action is completed the actual fuelling can start.
The fuel lines are narrow, so it takes a certain time and during this interval the operators, in their protective suits (weighing between 10 and 15 kg) stay close to the valves, ready to intervene.
Everything is supervised (remotely) by the test conductor and by CSG safety personnel.
I can take this picture because the images from the clean room are relayed to our office. This means we can follow the ongoing work. Regular safety announcements resonate throughout the area, alerting us on the start and end of safety critical operations. In case of any problem (radio, ventilation in the suit, air supply, propellant problems, etc.) specially trained staff (firemen from Pompiers de Paris) are close by, ready to react.