He had observed Halley's Comet in 1301 and was inspired to depict it as the star of Bethlehem in his painting Adoration of the Magi in the Scrovegni Chapel.

Members of the ESA’s Solar System Working Group started investigating a mission to Halley’s comet in 1977 before rejecting it in August 1978 in favour of a lunar orbiter.

[3] Shortly afterwards this was reversed by the Science Advisory Committee and the ESA started to study a joint mission with NASA.

[6] Named HAPPEN it involved using parts for a planned Geos-3 satellite to first examine the earth's Magnetotail before flying through the tail of Halley’s comet in march 1986.

[9] There were plans to have observation equipment on board a Space Shuttle in low-Earth orbit around the time of Giotto's fly-by, but they in turn fell through with the Challenger disaster.

Because Giotto would pass so very close to the nucleus ESA was mostly convinced it would not survive the encounter due to the spacecraft colliding at very high speed with the many dust particles from the comet.

[11][12] The mission was given the go-ahead by ESA in 1980, and launched on an Ariane 1 rocket (flight V14) on 2 July 1985 from Kourou, French Guiana.

Giotto passed Halley successfully on 14 March 1986 at 596 km distance, and surprisingly survived despite being hit by some small particles.

Giotto was commanded to wake up on 2 July 1990 when it flew by Earth in order to sling shot to its next cometary encounter.

Analysis showed the comet formed 4.5 billion years ago from volatiles (mainly ice) that had condensed onto interstellar dust particles.

[15] The quantity of material ejected was found to be three tonnes per second[16] for seven jets, and these caused the comet to wobble over long time periods.

[13] The ratio of abundances of the comet's light elements excluding nitrogen (i.e. hydrogen, carbon, oxygen) were the same as the Sun's.