No-one expected the spacecraft to survive its battering from comet dust during this encounter. However, although Giotto was damaged during the flyby, most of its instruments remained operational. To the scientists' delight, the mission was extended to allow an unprecedented encounter with a second comet, Grigg-Skjellerup. In 1992, after a long hibernation, Giotto was reawakened for the closest ever cometary flyby.

The major objectives of the original mission were to:

• Obtain the first close-up images of a comet nucleus
• Determine the elemental and isotopic composition of ices in the cometary coma
• Study the physical and chemical processes that occur in the comet's atmosphere
• Determine the elemental and isotopic composition of cometary dust particles
• Measure the comet's total gas-production rate
• Measure the amount of dust around the comet and its size/mass distribution
• Determine the relative amounts of dust and gas in the near-comet environment
• Investigate the interaction between the comet and the electrically charged particles of the solar wind