Originally a United States partner probe was planned that would accompany Giotto,but this fell through due to budget cuts at NASA. There were plans to have observation equipment on board a Space Shuttle in low-Earth orbit around the time of Giotto's fly-by,but they in turn fell through with the Challenger disaster.
The plan then became a cooperative armada of five space probes including Giotto,two from the Soviet Union's Vega program and two from Japan:the Sakigake and Suisei probes. The idea was for Japanese probes and the pre-existing American probe International Cometary Explorer 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 the spacecraft colliding at very high speed with the many dust particles from the comet. The coordinated group of probes became known as the Halley Armada.
Design
An image of the Giotto spacecraft during construction
The cylindrical spacecraft was 1.85m in diameter and had three internal platforms. It was derived from the GEOS research satellite built by British Aerospace in Filton, Bristol, and modified with the addition of a dust shield (Whipple shield) as proposed by Fred Whipple. The shield comprised a thin (1mm) aluminium sheet separated by a space and a thicker (12mm) Kevlar sheet.[3] The later Stardust spacecraft would use a similar Whipple shield. Giotto also had a 1.51m diameter antenna that it used to communicate with Earth.[3] A mock-up of the spacecraft resides at the Bristol Aero Collection hangar, at Filton, Bristol, England.[citation needed]
HMC (Halley Multicolour Camera): a 16-cm telescope and camera
DID (Dust Impactor Detector System): measured the mass of dust particles that hit the instrument
RPA (Rème Plasma Analyser): studied solar wind and charged particles
JPA (Johnstone Plasma Analyser): also measured solar wind and charged particles
PIA (Particulate Impact Analyser): studied the size and chemistry of particles
OPE (Optical Probe Experiment): examined the emissivity of gas and dust behind the spacecraft
EPA (Energetic Particle Analyser): analyzed alpha-particles, electrons, and neutrons
NMS (Neutral Mass Spectrometer): measured the composition of the particles around the comet
IMS (Ion Mass Spectrometer): measured the amount of ions from the sun and the comet
GRE (Giotto Radio Experiment): used Giotto's radio signals to study Halley's comet
Timeline
Launch
The mission was given the go-ahead by ESA in 1980, and launched on an Ariane 1 rocket (flight V14) on 2 July 1985 from Kourou, French Guiana. The craft was controlled from the European Space Agency ESOC facilities in Darmstadt (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, the ABM for Giotto was fired at perigee. Attitude determination and control used sun pulse and IR Earth sensor data in the telemetry to determine the spacecraft orientation.
Halley encounter
The SovietVega 1 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 making its flyby on 9 March. Vega 1's closest approach to Halley was 8889km.
Giotto passed Halley successfully on 14 March 1986 at 596km 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 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.
Comet Halley at Giotto spacecraft's 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 on 10 July 1992 which it approached to a distance of about 200km. Afterwards, Giotto was again switched off on 23 July 1992.
Second Earth flyby
In 1999 Giotto made another Earth flyby but was not reactivated.
Scientific results
Images showed Halley's nucleus to be a dark peanut-shaped body, 15km long, 7km to 10km 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 billion years ago from volatiles (mainly ice) that had condensed onto interstellar dust particles. It had remained practically unaltered since its formation.
Giotto found Halley's nucleus was dark, which suggested a thick covering of dust.[6]
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.[6] Sagdeev's team estimated a density of 0.6 g/cm3,[7] but S. J. Peale warned that all estimates had error bars too large to be informative.[8]
The quantity of material ejected was found to be three tonnes per second[9] for seven jets, and these caused the comet to wobble over long time periods.[6]
The dust ejected was mostly only the size of cigarette smoke particles, with masses ranging from 10 ag to 0.4 g. (See Orders of magnitude (mass).) The mass of the particle that impacted Giotto and sent it spinning was not measured, but from its effects—it also probably broke off a piece of Giotto[9]—the mass has been estimated to lie between 0.1g and 1g.[6]
Two kinds of dust were seen: one with carbon, hydrogen, nitrogen and oxygen; the other with calcium, iron, magnesium, silicon and sodium.[6]
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's Comet and provided the best data for this comet.[10]
Giotto was the first spacecraft:
to provide detailed pictures of a cometary nucleus.[11]
to make a close flyby of two comets. Young and active comet Halley could be compared to old comet 26P/Grigg–Skjellerup.
to return from interplanetary space and perform an Earth swing-by.
↑ Curdt, W.; Wilhelm, K.; Craubner, A.; Krahn, E.; Keller, H. U. (February 1988). "Position of comet P/Halley at the Giotto encounter". Astronomy and Astrophysics. 191 (1): L1–L3. Bibcode:1988A&A...191L...1C. ISSN0004-6361.
↑ Keller, H. U.; Arpigny, C.; Barbieri, C.; Bonnet, R. M.; Cazes, S.; Coradini, M.; Cosmovici, C. B.; Delamere, W. A.; etal. (15 May 1986). "First Halley Multicolour Camera imaging results from Giotto". Nature. 321 (6067s): 320–326. Bibcode:1986Natur.321..320K. doi:10.1038/321320a0. S2CID120631677.
Payloads are separated by bullets ( · ), launches by pipes ( | ). Crewed flights are indicated in underline. Uncatalogued launch failures are listed in italics. Payloads deployed from other spacecraft are denoted in (brackets).
Halley's Comet, Comet Halley, or sometimes simply Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–79 years. Halley is the only known short-period comet that is consistently visible to the naked eye from Earth. It last appeared in the inner parts of the Solar System in 1986 and will next appear in mid-2061.
Ulysses was a robotic space probe whose primary mission was to orbit the Sun and study it at all latitudes. It was launched in 1990 and made three "fast latitude scans" of the Sun in 1994/1995, 2000/2001, and 2007/2008. In addition, the probe studied several comets. Ulysses was a joint venture of the European Space Agency (ESA) and the United States' National Aeronautics and Space Administration (NASA), under leadership of ESA with participation from Canada's National Research Council. The last day for mission operations on Ulysses was 30 June 2009.
The Comet Nucleus Tour (CONTOUR) was a NASA Discovery-class space probe that failed shortly after its July 2002 launch. It was the only Discovery mission to fail.
Rosetta was a space probe built by the European Space Agency launched on 2 March 2004. Along with Philae, its lander module, Rosetta performed a detailed study of comet 67P/Churyumov–Gerasimenko (67P). During its journey to the comet, the spacecraft performed flybys of Earth, Mars, and the asteroids 21 Lutetia and 2867 Šteins. It was launched as the third cornerstone mission of the ESA's Horizon 2000 programme, after SOHO / Cluster and XMM-Newton.
Vega 1 was 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 Centre and constructed as 5VK by Lavochkin at Khimki. The name VeGa (ВеГа) combines the first two letters from the Russian words for Venus and Halley.
The Vega program was a series of Venus missions that also took advantage of the appearance of comet 1P/Halley in 1986. Vega 1 and Vega 2 were uncrewed spacecraft launched in a cooperative effort among the Soviet Union and Austria, Bulgaria, France, Hungary, the German Democratic Republic, Poland, Czechoslovakia, and the Federal Republic of Germany in December 1984. They had a two-part mission to investigate Venus and also flyby Halley's Comet.
Vega 2 was a Soviet space probe part of the Vega program to explore Halley's comet and Venus. The spacecraft was a development of the earlier Venera craft. The name VeGa (ВеГа) combines the first two letters Russian words for Venus and Halley They were designed by Babakin Space Centre and constructed as 5VK by Lavochkin at Khimki. The craft was powered by large twin solar panels. Instruments included an antenna dish, cameras, spectrometer, infrared sounder, magnetometers (MISCHA) and plasma probes. The 4,840 kilograms (10,670 lb) craft was launched on top of a Proton 8K82K rocket from Baikonur Cosmodrome, Tyuratam, Kazakh SSR. Both Vega 1 and 2 were three-axis stabilized spacecraft. The spacecraft were equipped with a dual bumper shield for dust protection from Halley's Comet.
Stardust was a 385-kilogram robotic space probe launched by NASA on 7 February 1999. Its primary mission was to collect dust samples from the coma of comet Wild 2, as well as samples of cosmic dust, and return them to Earth for analysis. It was the first sample return mission of its kind. En route to Comet Wild 2, it also flew by and studied the asteroid 5535 Annefrank. The primary mission was successfully completed on 15 January 2006 when the sample return capsule returned to Earth.
Sakigake, known before launch as 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. It aimed to demonstrate the performance of the new launch vehicle, test its ability to escape from Earth gravity, and observe the interplanetary medium and magnetic field. Sakigake was also supposed to act as a frame of reference for data received from probes that flew closer to Halley's Comet. Early measurements would be used to improve the mission of the Suisei probe launched several months later.
Deep Impact was a NASA space probe launched from Cape Canaveral Air Force Station on January 12, 2005. It was designed to study the interior composition of the comet Tempel 1 (9P/Tempel), by releasing an impactor into the comet. At 05:52 UTC on July 4, 2005, the Impactor successfully collided with the comet's nucleus. The impact excavated debris from the interior of the nucleus, forming an impact crater. Photographs taken by the spacecraft showed the comet to be more dusty and less icy than had been expected. The impact generated an unexpectedly large and bright dust cloud, obscuring the view of the impact crater.
The coma is the nebulous envelope around the nucleus of a comet, formed when the comet passes near the Sun in its highly elliptical orbit. As the comet warms, parts of it sublimate; this gives a comet a diffuse appearance when viewed through telescopes and distinguishes it from stars. The word coma comes from the Greek κόμη (kómē), which means "hair" and is the origin of the word comet itself.
Suisei, originally known as Planet-A, was an uncrewed space probe developed by the Institute of Space and Astronautical Science.
The Comet Rendezvous Asteroid Flyby (CRAF) was a cancelled plan for a NASA-led exploratory mission designed by the Jet Propulsion Laboratory during the mid-to-late 1980s and early 1990s, that planned to send a spacecraft to encounter an asteroid, and then to rendezvous with a comet and fly alongside it for nearly three years. The project was eventually canceled when it went over budget; most of the money still left was redirected to its twin spacecraft, Cassini–Huygens, destined for Saturn, so it could survive Congressional budget cutbacks. Most of CRAF's scientific objectives were later accomplished by the smaller NASA spacecraft Stardust and Deep Impact, and by ESA's flagship Rosetta mission.
The Solar Orbiter (SolO) is a Sun-observing probe developed by the European Space Agency (ESA) with a National Aeronautics and Space Administration (NASA) contribution. Solar Orbiter, designed to obtain detailed measurements of the inner heliosphere and the nascent solar wind, will also perform close observations of the polar regions of the Sun which is difficult to do from Earth. These observations are important in investigating how the Sun creates and controls its heliosphere.
The International Cometary Explorer (ICE) spacecraft, was launched 12 August 1978, into a heliocentric orbit. It was one of three spacecraft, along with the mother/daughter pair of ISEE-1 and ISEE-2, built for the International Sun-Earth Explorer (ISEE) program, a joint effort by NASA and ESRO/ESA to study the interaction between the Earth's magnetic field and the solar wind.
The Halley Armada is the name of a series of space probes, five of which were successful, sent to examine Halley's Comet during its 1986 sojourn through the inner Solar System, connected with apparition "1P/1982 U1". The armada included one probe from the European Space Agency, two probes that were joint projects between the Soviet Union and France and two probes from the Institute of Space and Astronautical Science in Japan. Notably, NASA did not contribute a probe to the Halley Armada.
Comet dust refers to cosmic dust that originates from a comet. Comet dust can provide clues to comets' origin. When the Earth passes through a comet dust trail, it can produce a meteor shower.
The nucleus is the solid, central part of a comet, formerly termed a dirty snowball or an icy dirtball. A cometary nucleus is composed of rock, dust, and frozen gases. When heated by the Sun, the gases sublime and produce an atmosphere surrounding the nucleus known as the coma. The force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun. A typical comet nucleus has an albedo of 0.04. This is blacker than coal, and may be caused by a covering of dust.
The Max Planck Institute for Solar System Research is a research institute in astronomy and astrophysics located in Göttingen, Germany, where it relocated in February 2014 from the nearby village of Lindau. The exploration of the Solar System is the central theme for research done at this institute.
Space dust measurement refers to the study of small particles of extraterrestrial material, known as micrometeoroids or interplanetary dust particles (IDPs), that are present in the Solar System. These particles are typically of micrometer to sub-millimeter size and are composed of a variety of materials including silicates, metals, and carbon compounds. The study of space dust is important as it provides insight into the composition and evolution of the Solar System, as well as the potential hazards posed by these particles to spacecraft and other space-borne assets. The measurement of space dust requires the use of advanced scientific techniques such as secondary ion mass spectrometry (SIMS), optical and atomic force microscopy (AFM), and laser-induced breakdown spectroscopy (LIBS) to accurately characterize the physical and chemical properties of these particles.
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