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Giotto launches
first close-up imaging of a comet nucleus
July 2, 1985ESA
ESA / MPS (Halley Multicolour Camera, Giotto)
The world that day
4.5 billion
People on Earth
2
Nations to launch a human
12
Humans to walk on the Moon
0
Known worlds beyond the Sun
On 2 July 1985 an Ariane 1 rose from Kourou carrying the first European spacecraft ever sent into deep space, bound for an appointment fixed by celestial mechanics seventy-six years in advance. Halley's Comet was coming back, as it has once a human lifetime throughout recorded history, and for the first time something built by people was going out to meet it. ESA named the probe Giotto, after Giotto di Bondone, the Italian master who saw the comet blaze over Padua in 1301 and painted it into his Scrovegni Chapel fresco of the Nativity as the Star of Bethlehem.
The encounter, on the night of 13 to 14 March 1986, was a calculated act of daring. Giotto closed on the comet at about 68 kilometres per second, a speed at which a one-gram dust grain strikes with devastating energy, protected only by two shield sheets of aluminium and Kevlar set 23 centimetres apart. Its instruments logged some 12,000 dust impacts on the way in. Then, just 7.6 seconds before closest approach, a large grain struck and sent the spacecraft spinning. In ESA's control centre at Darmstadt, and on live television across Europe, the screens went blank.
Giotto refused to die. Bursts of signal flickered back within moments, and over the next 32 minutes its thrusters steadied the wobble until contact was fully restored. The spacecraft had passed just 596 kilometres from the nucleus, and its pictures, the first close-up images of a comet's heart ever taken, were astonishing: a dark, irregular body venting bright jets of gas and dust from a few active patches on an otherwise quiet crust. The textbook 'dirty snowball' turned out to be one of the darkest objects known in the solar system, blacker than coal.
Even then the story continued. Placed into hibernation, Giotto was reawakened and steered past Earth on 2 July 1990, five years to the day after launch, the first time a spacecraft returning from interplanetary space used Earth for a gravity assist. On 10 July 1992 it flew within roughly 100 to 200 kilometres of comet Grigg-Skjellerup, the closest cometary flyby ever performed. Battered and half-blind but still working, Europe's first deep-space probe ended its career as the first spacecraft to visit two comets.
By the numbers
- Launch
- 2 Jul 1985, Ariane 1 from Kourou
- Spacecraft mass
- 960 kg
- Halley closest approach
- 596 km, night of 13–14 Mar 1986
- Encounter speed
- ~68 km/s relative to the comet
- Dust impacts recorded
- ~12,000
- Second comet flyby
- Grigg-Skjellerup, 10 Jul 1992, within ~200 km
Why it mattered
Giotto gave humanity its first look at the actual body of a comet and overturned the prevailing picture in a single night: the nucleus was not a bright snowball but a coal-black, crusted object venting from isolated jets, a finding that reshaped theories of comet structure and the early solar system. As ESA's first deep-space mission, it proved Europe could plan, fly and survive a high-risk interplanetary encounter, building the confidence and expertise that led directly to Rosetta's comet landing three decades later. Its post-Halley afterlife pioneered spacecraft hibernation, Earth-return gravity assists and multi-comet exploration on a single platform.
- The probe is named for the painter Giotto di Bondone, who witnessed Halley's 1301 apparition and worked it into his Scrovegni Chapel fresco as the Star of Bethlehem.
- Just 7.6 seconds before closest approach, a roughly one-gram dust grain sent the spacecraft spinning and knocked it off the air while Europe watched live; thrusters took 32 minutes to fully restore contact.
- Its survival kit was a double dust shield of aluminium and Kevlar sheets spaced 23 centimetres apart, designed to stop one-gram particles arriving at 68 kilometres per second.
- Giotto revealed Halley's nucleus to be darker than coal, among the darkest objects known in the solar system, with jets erupting from only a small fraction of the surface.
- It returned to Earth on 2 July 1990, exactly five years after launch, for the first gravity assist by a spacecraft coming home from interplanetary space, then made the closest comet flyby ever at Grigg-Skjellerup in 1992.
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