Giotto mission

Giotto mission

Overview
Giotto was a Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

an robotic spacecraft
Robotic spacecraft
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

 mission from the European Space Agency
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...

, intended to fly by and study Halley's Comet
Comet Halley
Halley's Comet or Comet Halley is the best-known of the short-period comets, and is visible from Earth every 75 to 76 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth, and thus the only naked-eye comet that might appear twice in a human lifetime...

. On 13 March 1986, the mission succeeded in approaching Halley's nucleus at a distance of 596 kilometers.
The spacecraft was named after the Early Italian Renaissance
Italian Renaissance
The Italian Renaissance began the opening phase of the Renaissance, a period of great cultural change and achievement in Europe that spanned the period from the end of the 13th century to about 1600, marking the transition between Medieval and Early Modern Europe...

 painter
Painting
Painting is the practice of applying paint, pigment, color or other medium to a surface . The application of the medium is commonly applied to the base with a brush but other objects can be used. In art, the term painting describes both the act and the result of the action. However, painting is...

 Giotto di Bondone
Giotto di Bondone
Giotto di Bondone , better known simply as Giotto, was an Italian painter and architect from Florence in the late Middle Ages...

. He had observed Halley's Comet in 1301 and was inspired to depict it as the star of Bethlehem
Star of Bethlehem
In Christian tradition, the Star of Bethlehem, also called the Christmas Star, revealed the birth of Jesus to the magi, or "wise men", and later led them to Bethlehem. The star appears in the nativity story of the Gospel of Matthew, where magi "from the east" are inspired by the star to travel to...

 in his painting Adoration of the Magi.


Originally a United States partner probe was planned that would accompany Giotto, but this fell through due to budget cuts at NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

.
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Encyclopedia
Giotto was a Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

an robotic spacecraft
Robotic spacecraft
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

 mission from the European Space Agency
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...

, intended to fly by and study Halley's Comet
Comet Halley
Halley's Comet or Comet Halley is the best-known of the short-period comets, and is visible from Earth every 75 to 76 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth, and thus the only naked-eye comet that might appear twice in a human lifetime...

. On 13 March 1986, the mission succeeded in approaching Halley's nucleus at a distance of 596 kilometers.
The spacecraft was named after the Early Italian Renaissance
Italian Renaissance
The Italian Renaissance began the opening phase of the Renaissance, a period of great cultural change and achievement in Europe that spanned the period from the end of the 13th century to about 1600, marking the transition between Medieval and Early Modern Europe...

 painter
Painting
Painting is the practice of applying paint, pigment, color or other medium to a surface . The application of the medium is commonly applied to the base with a brush but other objects can be used. In art, the term painting describes both the act and the result of the action. However, painting is...

 Giotto di Bondone
Giotto di Bondone
Giotto di Bondone , better known simply as Giotto, was an Italian painter and architect from Florence in the late Middle Ages...

. He had observed Halley's Comet in 1301 and was inspired to depict it as the star of Bethlehem
Star of Bethlehem
In Christian tradition, the Star of Bethlehem, also called the Christmas Star, revealed the birth of Jesus to the magi, or "wise men", and later led them to Bethlehem. The star appears in the nativity story of the Gospel of Matthew, where magi "from the east" are inspired by the star to travel to...

 in his painting Adoration of the Magi.

Mission



Originally a United States partner probe was planned that would accompany Giotto, but this fell through due to budget cuts at NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

. There were plans to have observation equipment on-board a Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

 in low-Earth orbit around the time of Giotto's fly-by, but they in turn fell through with the Challenger disaster
STS-51-L
STS-51-L was the twenty-fifth flight of the American Space Shuttle program, which marked the first time an ordinary civilian, schoolteacher Christa McAuliffe, had flown aboard the Space Shuttle. The mission used Space Shuttle Challenger, which lifted off from the Launch Complex 39-B on 28 January...

.

The plan then became a cooperative armada of five spaceprobes including Giotto, two from the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

's Vega program
Vega program
The Vega program was a series of Venus missions which also took advantage of the appearance of Comet Halley in 1986. Vega 1 and Vega 2 were unmanned spacecraft launched in a cooperative effort among the Soviet Union and Austria, Bulgaria, Hungary, the German Democratic Republic, Poland,...

 and two from Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

: the Sakigake
Sakigake
Sakigake , pre-launch codename MS-T5, was Japan's first interplanetary spacecraft, and the first deep space probe to be launched by any country other than the USA or the Soviet Union...

 and Suisei probe
Suisei probe
Suisei , originally known as Planet-A, was an unmanned space probe developed by the Institute of Space and Astronautical Science ....

s. The idea was for Japanese probes and the pre-existing American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 probe International Cometary Explorer
International Cometary Explorer
The International Cometary Explorer spacecraft was originally known as International Sun/Earth Explorer 3 satellite, launched August 12, 1978. It was part of the ISEE international cooperative program between NASA and ESRO/ESA to study the interaction between the Earth's magnetic field and the...

 to make long distance measurements, followed by the Russian Vegas which would locate the nucleus, and the resulting information sent back would allow Giotto to precisely target very close to the nucleus. Because Giotto would pass so very close to the nucleus ESA was mostly convinced it would not survive the encounter due to bombardment from the many high speed cometary particles. The coordinated group of probes became known as the Halley Armada
Halley Armada
The Halley Armada is the generally accepted and popularly used name of five space probes sent to examine Halley's Comet during its 1986 sojourn through the inner solar system, connected with apparition "1P/1982 U1"...

.

The craft


The spacecraft was derived from the GEOS research satellite built by British Aerospace, and modified with the addition of a dust shield as proposed by Fred Whipple which comprised a thin (1 mm) aluminium sheet separated by a space and a thicker Kevlar
Kevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...

 sheet. The later Stardust spacecraft
Stardust (spacecraft)
Stardust is a 300-kilogram robotic space probe launched by NASA on February 7, 1999 to study the asteroid 5535 Annefrank and collect samples from the coma of comet Wild 2. The primary mission was completed January 15, 2006, when the sample return capsule returned to Earth...

 would use a similar Whipple shield. A mock up of the spacecraft resides at the Bristol Aero Collection hanger, at Kemble Airport, UK.

Launch


The mission was given the go-ahead by ESA in 1980, and launched
on an Ariane 1
Ariane 1
Ariane 1 is the first version of the Ariane launcher family. Ariane 1 was designed primarily to put two telecommunications satellites at a time into orbit, thus reducing costs. As the size of the satellites grew Ariane 1 gave way to the more powerful Ariane 2 and Ariane 3 launchers.- Vehicle...

 rocket (flight V14) on 2 July 1985 from Kourou
Kourou
Kourou is a commune in French Guiana, an overseas region and department of France located in South America.Kourou is the location of the Guiana Space Centre, France and ESA's main spaceport.-Geography:...

. The craft was controlled from the European Space Agency ESOC facilities
European Space Operations Centre
The European Space Operations Centre is responsible for controlling ESA satellites and space probes. The centre is located in Darmstadt, Germany. It is Mission Control for most of the space projects of the ESA. Since its creation in 1967, the centre has operated 60 European space missions...

 in Darmstadt
Darmstadt
Darmstadt is a city in the Bundesland of Hesse in Germany, located in the southern part of the Rhine Main Area.The sandy soils in the Darmstadt area, ill-suited for agriculture in times before industrial fertilisation, prevented any larger settlement from developing, until the city became the seat...

 (then West Germany) initially in Geostationary Transfer Orbit (GTO) then in the Near Earth Phase (NEP) before the longer Cruise Phase through to the encounter. While in GTO a number of slew and spin-up manoeuvres (to 90 RPM) were carried out in preparation for the firing of the Apogee Boost Motor (ABM), although unlike orbit circularisations for geostationary orbit
Geostationary orbit
A geostationary orbit is a geosynchronous orbit directly above the Earth's equator , with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero. An object in a geostationary orbit appears motionless, at a fixed position in the sky, to ground observers...

, the ABM for Giotto was fired at perigee
Perigee
Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...

. Attitude determination and control used sun pulse and IR earth sensor data in the telemetry to determine the spacecraft orientation.

Halley encounter


The Soviet
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 Vega 1
Vega 1
Vega 1 is a Soviet space probe part of the Vega program. The spacecraft was a development of the earlier Venera craft...

 started returning images of Halley on 4 March 1986, and the first ever of its nucleus, and made its flyby on 6 March, followed by Vega 2
Vega 2
Vega 2 is a Soviet space probe part of the Vega program. The spacecraft was a development of the earlier Venera craft. They were designed by Babakin Space Center and constructed as 5VK by Lavochkin at Khimki...

 making its flyby on 9 March. The Vega 1 closest approach to Halley was
8 889 km.

Giotto passed Halley successfully on 14 March 1986 at 596 km distance, and surprisingly survived despite being hit by some small particles. One impact sent it spinning off its stabilized spin axis so that its antenna no longer always pointed at the Earth, and importantly, its dust shield no longer protected its instruments. After 32 minutes Giotto re-stabilized itself and continued gathering science data.

Another impact destroyed the Halley Multicolor Camera, but not before it took photographs of the nucleus at closest approach.

First Earth flyby


Giotto's trajectory was adjusted for an Earth flyby and its science instruments were turned off on 15 March 1986 at 02:00 UTC.

Grigg-Skjellerup encounter


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.

The probe then flew by the Comet Grigg-Skjellerup
26P/Grigg-Skjellerup
Comet Grigg–Skjellerup is a periodic comet.Discovered in 1902 by John Grigg of New Zealand, and rediscovered in its next appearance in 1922 by John Francis Skjellerup, an Australian then living and working for about two decades in South Africa where he was a founder member of the Astronomical...

 in 10 July 1992 which it approached to a distance of about 200 km. Afterwards, Giotto was again switched off on 23 July 1992.

Scientific results


Images showed Halley's nucleus to be a dark peanut-shaped body, 15 km long, 7 km to 10 km wide. Only 10 % of the surface was active, with at least three outgassing jets seen on the sunlit side. Analysis showed the comet formed 4.5 x 109 years ago from volatiles (mainly ice) that had condensed onto interstellar dust particles. It had remained practically unaltered since its formation.

Measured volume of material ejected by Halley:
  • 80 % water
    Water
    Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

    ,
  • 10 % carbon monoxide
    Carbon monoxide
    Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

  • 2.5 % A mix of methane
    Methane
    Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

     and ammonia
    Ammonia
    Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

    .
  • Other hydrocarbon
    Hydrocarbon
    In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

    s, iron
    Iron
    Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

    , and sodium
    Sodium
    Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

     were detected in trace amounts.


Giotto found Halley's nucleus was blacker than coal, which suggested a thick covering of dust.

The nucleus's surface was rough and of a porous quality, with the density of the whole nucleus as low as 0.3 g/cm³. Sagdeev's team estimated a density of
0.6 g/cm³, but S. J. Peale warned that all estimates had error bars too large to be informative.

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

The dust ejected was mostly only the size of cigarette smoke particles, with masses ranging from
Orders of magnitude (mass)
To help compare different orders of magnitude, the following list describes various mass levels between 10−36 kg and 1060 kg.-Units of mass:...

 10 ag to 0.4 g. (See Orders of magnitude (mass)
Orders of magnitude (mass)
To help compare different orders of magnitude, the following list describes various mass levels between 10−36 kg and 1060 kg.-Units of mass:...

.) Although the one particle impact that sent Giotto spinning was not measured, from its effects - it also probably broke off a piece of Giotto - its mass has been estimated to lie between 0.1 g and 1 g.

Two kinds of dust were seen: one with carbon, hydrogen, nitrogen and oxygen; the other with calcium, iron, magnesium, silicon and sodium.

The ratio of abundances of the comet's light elements excluding nitrogen (i.e. hydrogen, carbon, oxygen) were the same as the Sun's. The implication is that the constituents of Halley are among the most primitive in the solar system.

The plasma and ion mass spectrometer instruments showed Halley has a carbon-rich surface.

Spacecraft achievements

  • Giotto made the closest approach to Halley comet and provided the best data for this comet.
  • Giotto was the first spacecraft to provide detailed pictures of a cometary nucleus.
  • Giotto was the first spacecraft do a close flyby of two comets. Young and active comet Halley could be compared to old Grigg-Skjellerup.
  • Giotto was the first spacecraft to return from interplanetary space and perform an Earth swing by.
  • Giotto was the first spacecraft to be re-activated from hibernation mode.

External links