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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?
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I suppose Apollo 13 did not officially enter hibernation mode, then? – Michael Kjörling Feb 7 '14 at 12:24
up vote 6 down vote accepted

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.
The wakeup took several days. After the wakeup, Giotto aimed its main antenna at Earth for new instructions.
A recent question about Rosetta shows that a different approach was used there.

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