Giotto (spacecraft)

Main article: Giotto (spacecraft)

Further information: European Space Agency

Mission Overview

Giotto was a European robotic spacecraft. It was sent by the European Space Agency to study Halley's Comet. Giotto became the first spacecraft to get close to a comet.

Key Event

On 13 March 1986, Giotto flew very close to Halley's Comet. It got as near as 596 kilometers to the comet's center.

Naming

The spacecraft was named after an Early Italian Renaissance painter called Giotto di Bondone. Long ago, he saw Halley's Comet in 1301. He thought it looked like the star of Bethlehem and painted it in a famous artwork.

Mission

Development

Members of the European Space Agency’s Solar System Working Group started planning a mission to study Halley’s Comet in 1977. The European Space Agency decided to work with NASA on a joint mission called the International Comet Mission. This mission would have included a NASA probe and a smaller European probe. But the NASA part of the mission was cancelled in 1979.

Later, a new plan was made to launch the mission using an Ariane 1 rocket. Different ideas were suggested, and finally, a mission named Giotto was chosen. The mission was approved in July 1980 with a budget of 80 million accounting units.

In 1981, British Aerospace offered a design for the spacecraft, but it was rejected because of problems with power and temperature control. The design was also outdated, so a new, slightly larger spacecraft was created, with British Aerospace still leading the project.

Originally, Giotto was supposed to launch with another satellite on an Ariane 2 rocket, but this changed. It was then planned to launch on an Ariane 3, but because no customer wanted to launch during the needed time, Giotto was assigned to fly alone on an Ariane 1 rocket.

There were also plans to use equipment on a Space Shuttle in orbit during Giotto’s fly-by, but these plans fell through after the Challenger disaster.

The final plan was for a group of five space probes to study Halley’s Comet together. This group, called the Halley Armada, included Giotto, two probes from the Soviet Union’s Vega program, and two from Japan: the Sakigake and Suisei probes. The American probe International Cometary Explorer would also help. The Soviet probes would find the comet’s nucleus, and Giotto would then fly very close to it. Because Giotto would pass so close, there was a chance it might not survive due to dust particles from the comet.

Design

The Giotto spacecraft was shaped like a cylinder. It was 1.87 meters wide and 2.85 meters long. It was built by British Aerospace in Filton, Bristol. It had a special shield to protect it from dust. This shield had two layers: a thin aluminium sheet and a thicker Kevlar sheet. Giotto also had a large antenna to send messages back to Earth.

The spacecraft carried ten tools to study the comet. These included a camera and instruments to measure dust, particles, and gases around the comet. A model of Giotto can be seen at the Bristol Aero Collection hangar in Filton, Bristol, England.

Timeline

The European Space Agency got the Giotto spacecraft ready in April 1985. It was sent to French Guiana, and the camera followed soon after. The launch happened on July 2, 1985, on an Ariane 1 rocket from Kourou, French Guiana.

Giotto’s journey included testing its camera by taking pictures of the star Vega and Earth. In March 1986, it flew by Halley's Comet, getting very close to the comet. During this, Giotto faced some challenges but sent back important images and data.

After this, Giotto flew by Earth and later another comet named Grigg–Skjellerup in 1992.

Scientific results

Images from the spacecraft showed Halley's nucleus to be a dark, peanut-shaped body, about 15 kilometers long and 7 to 10 kilometers wide. Only a small part of its surface was active. Scientists learned that the comet formed about 4.5 billion years ago from icy materials that stuck to dust particles in space.

The spacecraft measured what the comet threw off, mostly water, with smaller amounts of carbon monoxide, methane, ammonia, and other materials. Halley's nucleus was found to be dark, suggesting it was covered in dust. The surface was rough and porous. The comet threw off a lot of material, causing it to wobble over time. Most of the dust particles were very small.

Spacecraft achievements

Giotto made the closest ever flyby of Halley's Comet and gave us the best data about this comet. It was the first spacecraft to give us detailed pictures of a comet's nucleus. It also was the first to fly close to two different comets, allowing scientists to compare them. Giotto used Earth's gravity to change its path and was brought back to life after resting in space.

Giotto II proposals

Scientists thought of ways to make a backup spacecraft. One idea was to use a probe like Giotto to collect a sample from a comet's atmosphere. They planned to bring the sample back to Earth in a special capsule, instead of using the Mage motor.