When controllers sent commands to the engine to turn itself on again last Tuesday, they planned to collect more data on the status of the system but believed it was unlikely the engine would keep running.

CNN: Deep Space probe's ion engine working smoothly, NASA says

It was three o'clock in the morning when Graham fired up the engine, and as the frost glistened on the young fruit, the giant rotor began to turn.

BBC: Graham Hewitt and his wind machine