The Wikipedia article on Giotto states that:
Giotto was the first spacecraft to be re-activated from hibernation mode.
- How was the reactivation accomplished?
- Does the statement mean the spacecraft restarted after a shutdown, or something else?
Giotto woke up from hibernation after a signal from ground control. This meant that at least the radio receiver and parts of the computer still had to be active. The science instruments and most of the spacecraft management systems (e.g. attitude control) were switched off.