Giotto (probe)

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Giotto

Artist's impression of Giotto with Halley
Mission goal Halley's Comet
Client European space agencyESA ESA
Launcher Ariane 1
construction
Takeoff mass 960 kg
Size: 1.1 × 1.1 × 2.85 m
Course of the mission
Start date July 2, 1985, 11:23 UTC
launch pad CSG , ELA-1
End date July 23, 1992
 
 07/02/1985 begin
 
 March 14, 1986 Passage from Halley
 
 07/02/1990 Fly by the earth
 
 July 10, 1992 Fly by Grigg-Skjellerup
 
 July 23, 1992 Deactivation

Giotto was a European unmanned space probe that was launched in 1985 to explore Comet Halley . It was " ESA's first interplanetary probe and the first scientific payload on board an Ariane rocket."

On the night of March 13-14, 1986, comet research luminaries Fred Whipple , Jan Hendrik Oort and Carl Sagan ( Ludwig Biermann had died two months earlier) met at the European Space Control Center in Darmstadt for the “most important space travel event since the moon landing” . This event was broadcast on 50 television stations; on ZDF until the early morning (something special back then).

Purpose of the mission

Giotto: Adorazione dei Magi (around 1305)

The Giotto space probe of the European Space Agency (ESA) was used to study Halley's Comet. The probe is named after the Italian painter Giotto di Bondone from the High Middle Ages. He observed the comet Halley in 1301 and probably depicted him as the star of Bethlehem in the fresco Adoration of the Three Kings .

Originally a US partner probe was supposed to accompany Giotto on the trip, but these budget cuts fell victim to NASA . A cooperation with the Soviet Union and Japan came about, which also sent probes with Vega  1 and 2 and Sakigake and Suisei . Since Giotto very close to the comet flying past would, ESA managers assumed that the probe, the Rendezvous very robust due to the "bombing" by comet particles in spite of, front shield would not survive. Therefore, all scientific data was transmitted live to Earth.

course

Giotto with the Whipple shield during construction

Giotto took off on July 2, 1985 at 11:23 UTC with an Ariane 1 rocket from the European spaceport in Kourou . The passage near Halley took place on March 14, 1986 at 00:03:02 UTC at a distance of only 596 km with a fly-by speed of 68.7 km / s (247,320 km / h), which was due to orbit corrections based on measurements from the other probes was made possible. Surprisingly, Giotto survived the close flyby of the comet, but was badly hit 7.6 seconds before the closest approach to Halley. The camera and some other instruments were immediately unusable or destroyed, but the wobbling space probe was able to catch itself again and stabilize within 30 minutes. The probe was programmed for a return flight to Earth and initially switched off.

In 1990 the probe was reactivated; a flyby of Earth took place on July 2, 1990, exactly five years after take-off.

On July 10, 1992, the probe passed a second comet, Grigg-Skjellerup (distance: 200 kilometers), after which the probe was redirected back to Earth and (permanently) deactivated on July 23, 1992. The second earth flyby took place on July 1, 1999, but the probe was not reactivated because of the almost exhausted fuel supply.

Results

Findings on Halley's Comet

Giotto's image of Halley's Comet

The photos made by Giotto show the core of Halley's Comet as a peanut-shaped, dark body 15 km long and 7-10 km wide. Only 10% of the surface is active, including at least three gas outbreaks on the side facing the sun. The analyzes showed that the comet was formed 4.5 billion years ago from ice that condensed on interstellar dust particles. Since then, its shape has essentially not changed.

The material ejected by the comet consists of 80% water , 10% carbon monoxide and 2.5% methane and ammonia . The rest includes traces of hydrocarbons , iron and sodium .

With an albedo of only 0.04, the comet's core is darker than coal and is one of the darkest objects in the solar system known to us so far. Its color suggests very large amounts of dust accumulated on the surface.

The surface of the core is rough and porous. Its density is only 0.3 g / cm³ (about a third of the density of water). The amount of matter emitted by seven gas jets is around 3 t / s. This mass ejection leads to tumbling rotary movements that can be stable over long periods of time.

The majority of the dust particles emitted are about the size of cigarette smoke particles and have a mass in the range of 10 −20  kg to 40 × 10 −5  kg (10 attograms to 40 milligrams). But there are also a few larger parts. A mass between 100 and 1,000 mg was calculated from the impact energy of a particle and the resulting course deviation of the probe.

In terms of chemical composition, dust can be divided into two groups. The first, the so-called CHON group, consists mainly of light elements such as carbon (C), hydrogen (H), oxygen (O) and nitrogen (N). The second group, on the other hand, has elements that are typically found in rocks and minerals: sodium , magnesium , silicon , iron and calcium .

It is noticeable that the ratio of light elements to silicon corresponds to that of the sun. It is therefore believed that Halley's Comet is made of the oldest, unconverted material in the solar system.

Success from the perspective of space travel

After the two German-US-American probes of the Helios program, Giotto was the first solely “European” probe.

  • Giotto flew closest to Halley comet and transmitted the best data and images of the comet yet.
  • The flyby of Comet Grigg-Skjellerup was the closest comet flyby in space history. It made it possible to compare this old comet with the young, active Halley. In addition, Giotto was the first probe to fly past two different comets
  • Giotto was the first probe to return to Earth from interplanetary space and use Earth for a swing-by maneuver.
  • Giotto was also the first space probe that was temporarily switched off during its mission and was left to its own devices (hibernation mode). This saved monitoring costs.
  • Giotto is considered a role model for future comet missions. The experience gained with it was also incorporated into the Rosetta comet probe launched on March 2, 2004 and its Philae lander .

See also

literature

  • Nigel Calder : Beyond Halley. The exploration of tail stars by the space probes Giotto and Rosetta (original title: Giotto to the Comets ). German by Daniel Fischer. Preface by Reimar Lüst . Springer, Berlin, Heidelberg and New York 1994, 234 (XVI) S., ISBN 3-540-57585-5
  • Hahn, Hermann-Michael (1985): The Giotto company. Geosciences in our time; 3 (6) ; 173-180. doi : 10.2312 / geosciences.1985.3.173 (PDF; 2.6 MB)

Web links

Commons : Giotto (probe)  - collection of images, videos and audio files

swell

  1. ↑ "And never before has a man-made vehicle come so close to a comet ... ESA has proven that the old continent no longer needs to hide when it comes to technology ..."; Helmut Hornung: The night of the comet. in: MaxPlanckResearch . 2/2014 , p. 74f.
  2. ↑ "The criticism {will} of the show from Mainz moderated by Joachim Bublath and Bernd Heller will not leave a good hair ... A lot of gossip and little science flickered across the screen for hours."; Helmut Hornung: The night of the comet. in: MaxPlanckResearch . 2/2014 , p. 74f.
  3. ^ ESA Science & Technology: Halley , accessed August 3, 2014.