Giotto (spacecraft)
Giotto was a European, unmanned spacecraft that was sent to the exploration of Halley's Comet into space in 1985.
Purpose of the mission
The Giotto spacecraft of the European Space Agency ( ESA) was the exploration of Halley 's Comet. Named the probe after the Italian painter Giotto di Bondone from the High Middle Ages. This observed Halley's Comet in 1301 and introduced him probably as a star of Bethlehem in the fresco Adoration of the Magi dar.
Originally an American partner Giotto probe accompany them on the journey, but this fell to budget cuts at NASA victim. Time, there was cooperation with the Soviet Union and Japan, which also sent probes Vega 1 and 2 and Sakigake and Suisei. Since Giotto would fly past very close to the comet, ESA managers assumed that the probe would not survive the rendezvous due to the " bombardment " by comets particles despite a very robust front shield. Therefore, all scientific data were transmitted live to earth.
Course
Giotto was launched on 2 July 1985 at 11:23:16 UTC by an Ariane 1 rocket from the European Spaceport in Kourou. The passage at Halley took place on 14 March 1986 at 00:03:02 UTC in only 596 km distance with a flyby speed of 68.7 km / s ( 247,320 km / h ), as indicated by path corrections based on measurements of the other probes was made possible. This Giotto survived surprisingly narrow flyby of the comet, but was 7.6 seconds before the closest approach to Halley hit hard. The camera and some other instruments were unusable or destroyed, but the lurching guessed spacecraft could begin again and stabilize within 30 minutes. The probe was programmed to return to Earth and initially turned off.
In 1990, the probe was then reactivated; a flyby of the Earth took place on 2 July 1990, which held exactly five years after the launch.
On 10 July 1992, the probe passed a second comet, Grigg - Skjellerup ( distance: 200 km ), then the probe was directed back again to the earth and on 23 July 1992 ( final) disabled. The second Earth swing took place on 1 July 1999, but the probe has not been reactivated due to the nearly exhausted fuel supply.
Results
Findings on Halley's Comet
The recordings made by Giotto show the core of Halley's comet as peanut -shaped, dark body of 15 km long and 7-10 km wide. Only 10 % of the surface are active, including at least three gas eruptions on the sun- facing side. The analyzes showed that the comet was created 4.5 billion years ago from ice that condensed on interstellar dust particles. Since then his form has not changed substantially.
The ejected from the comet material consists of 80 % water, 10% carbon monoxide and 2.5 % methane and ammonia. The rest contains traces of hydrocarbons, iron and sodium.
With an albedo of only 0.04 of the comet nucleus is darker than coal and is one of the darkest objects in the solar system that we know of so far. Its color is indicative of very large amounts of dust accreted on the surface.
The surface of the core is rough and porous. Its density is 0.3 kg / m³. The amount of the gas jets discharged by sieving material is about 3 t / p This mass ejection leads to wobbling rotational motions that can be stable over long periods of time.
, The bulk of the discharged dust particles is about the size of cigarette smoke particles, and a mass in the range of 10-20 kg to 40x10 -5 kg (10 attograms to 40 mg). But there are also a few larger pieces. As a mass between 100 and 1000 mg calculated as the impact energy of a particle and the resulting track error of the probe.
From the chemical composition, can the dust in two groups. The first, the so-called CHON group consisting mainly of light elements such as carbon (C ), hydrogen ( H), oxygen (O ) and nitrogen ( N). In contrast, the second group includes items that are typically found in rocks and minerals, sodium, magnesium, silicon, iron and calcium.
It is striking that the ratio of the light elements to silicon corresponds to the sun. It is believed, therefore, that Halley's comet is composed of the oldest, unconverted material of the solar system.
Success from the perspective of space
Giotto was after the two German -US probes of the Helios program, the first single "European" probe.
- Giotto flew most densely past the comet Halley and provided the best ever data and images of the comet.
- The flyby of comet Grigg - Skjellerup was the densest comet flyby of space history. He allowed a comparison of this ancient comet with the young, active Halley. In addition, Giotto was the first spacecraft flew past comet two different
- Giotto was the first spacecraft to return from interplanetary space to earth and took the earth for a swing-by maneuver.
- Giotto was the first spacecraft that was turned off during their mission at times and was left to itself. This monitoring costs were saved.
- Giotto is considered a model for future comet missions. So flowed the collected experiences with it also in the launched on 2 March 2004 Rosetta and its Philae lander.