Giotto second homecoming set for 1 July
30 June 1999
ESA's deactivated Giotto spacecraft will perform its second Earth flyby in the early hours of 1 July 1999, 14 years since its launch on 2 July 1985 and five years after its previous return to Earth's vicinity on 2 July 1990. Scientists estimate that it will sweep past approximately 220,000 km (just over half the Earth-Moon distance). The flyby coincides with a press briefing in London, on ESA's next cometary mission, Rosetta, which will be held later the same day.Giotto operations were officially terminated on 23 July 1992, after completion of final orbit adjustments and configuration of the spacecraft for its third hibernation. The spacecraft had about 15 kg of propellant left, barely enough to adjust the orbit for one last Earth flyby.
Travelling at a velocity of about 3.5 km/sec, Giotto will be closest to Earth at around 02.40 UTC(GMT) on 1 July. No attempt will be made to reawaken the sleeping spacecraft, but observers in the Southern Hemisphere may be able to detect it with large telescopes.
The trajectory relative to the Earth will be almost perpendicular to the equator. 15 hours before closest approach (perigee), Giotto will be within one degree of the South Pole direction. Although the spacecraft will be flying northwards, the Earth's rotation will cause Giotto's apparent motion to be mainly westwards. At perigee, it is expected to be vertically above the South Atlantic, between Tristan da Cunha and South Georgia. It will then fly over southern South America as it recedes from the Earth. It will cross over the equator 16 hours after perigee.
