Giotto

By Marty McDowell/NASA

On July 2, 1985, the European Space Agency (ESA) launched Giotto to study Halley's Comet. This was the first ESA deep space mission. On March 13, 1986, the Giotto spacecraft obtained the first close-up pictures of a comet nucleus during its close flyby of Halley's Comet. An historic second comet encounter followed on July 10, 1992 when Giotto flew within 200 km of Comet Grigg-Skjellerup.

Giotto was the European Space Agency’s contribution to an international space armada which was despatched to explore Halley’s Comet. Other spacecraft sent towards the comet were the Japanese Sakigake and Suisei, and the twin Soviet Vega 1 and 2, which dropped probes onto the surface of Venus en route.

The Vegas acted as pathfinders for Giotto, sending back images and other information which enabled ESA ground controllers to home in on the comet’s tiny nucleus. Financial cutbacks prevented NASA from carrying out a dedicated Halley mission, but several American spacecraft (e.g. the Pioneer Venus orbiter) were able to conduct long range studies.

ESA Out of focus, overexposed, and a complete lack of composition, but it was the best close-up picture we ever saw of Comet Halley! Image courtesy of ESA.

The purpose of the Giotto mission was to study Comet Halley during its closest passage to the Sun (known as perihelion) in 1986. 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.

Source: NASA.

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Space References (Videos):
Cosmos. PBS, 2000.
Stephen Hawking's Universe. PBS, 1997.
Hyperspace. BBC, 2002.
Life Beyond Earth PBS, 1999.
The Planets. BBC, 1999.
Understanding The Universe. A&E, 1996.