NASA - NSSDCA - Spacecraft - Details NSSDCA/COSPAR ID: 1985-056A Description The Giotto mission was designed to study Comet P/Halley. The major objectives of the mission were to: (1) obtain color photographs of the nucleus; (2) determine the elemental and isotopic composition of volatile components in the cometary coma, particularly parent molecules; (3) characterize the physical and chemical processes that occur in the cometary atmosphere and ionosphere; (4) determine the elemental and isotopic composition of dust particles; (5) measure the total gas-production rate and dust flux and size/mass distribution and derive the dust-to-gas ratio; and, (6) investigate the macroscopic systems of plasma flows resulting from the cometary-solar wind interaction. The spacecraft encountered the comet on March 13, 1986, at a distance of 0.89 AU from the sun and 0.98 AU from the Earth and an angle of 107 degrees from the comet-sun line. The spacecraft was based as much as possible on the ESA-GEOS spacecraft and was spin stabilized with a rate of 15 rpm.

During the encounter with Halley's comet, the spin axis was aligned with the relative velocity vector. The 1.5 m dish antenna, operating in the X-band, was inclined and despun in order to point at the Earth (44 degrees with respect to the velocity vector). The goal was to come within 500 km of Halley's comet at closest encounter. The actual closest approach was measured at 596 km. The main body of Giotto was a short cylinder 1.85 m in diameter by about 1.1 m in length, with three interior platforms. The top platform, 30 cm thick, a main platform, 40 cm, and an experiment platform, 30 cm. Each platform consisted of a disc within the cylinder on which was mounted subsystem and science apparatus. The cylinder was topped by a tripod which surrounded a high gain dish antenna and gave the spacecraft a total height of 2.85 m. The main rocket was positioned in the center of the cylinder with the nozzle protruding out the bottom.

The spacecraft had a dust shield consisting of a front sheet of aluminum (1 mm thick) and a 12 mm Kevlar near sheet separated by 25 cm, which could withstand impacts of particles up to 1 gram. The scientific payload was comprised of ten hardware experiments: a narrow-angle camera, three mass spectrometers for neutrals, ions and dust, various dust detectors, a photopolarimeter and a set of plasma experiments. All experiments performed well and returned a wealth of new scientific results, of which perhaps the most important was the clear identification of the cometary nucleus. Fourteen seconds before closest approach, Giotto was hit by a `large' dust particle. The impact caused the spacecraft angular momentum vector to shift by 0.9 degrees, and the spacecraft performed a nutation around the new axis with a period of 16 s and an amplitude of 0.9 degrees; thus, the maximum deviation from the desired attitude was 1.8 degrees. Scientific data were received intermittently for the next 32 minutes. Some experiment sensors suffered damage during this 32-minute interval.

Other experiments (the camera baffle and deflecting mirror, the dust detector sensors on the front sheet of the bumper shield, and most experiment apertures) were exposed to dust particles regardless of the accident and also suffered damage. Many of the sensors survived the encounter with little or no damage. Questionable or partially damaged sensors included the camera (later proved to not be functional) and one of the plasma analyzers (RPA). Inoperable experiments included the neutral and ion mass spectrometers and one sensor each on the dust detector and the other plasma analyzer (JPA). During the Giotto extended mission, the spacecraft flew by the Earth on 2 July 1990 at a distance of 16,300 km at 10:01:18 UTC. This was the first encounter of Earth by a spacecraft coming from deep space. During the encounter, observations were made of the Earth's magnetic field and energetic particles. Giotto obtained a gravitational assist from this flyby and successfully encountered Comet P/Grigg-Skjellerup on July 10, 1992. The closest approach was 200 km at a relative velocity of 13.99 km/s.

The heliocentric distance of the spacecraft was 1.01 AU, and the geocentric distance, 1.43 AU at the time of the encounter. The payload was switched on in the evening of July 9. Eight experiments were operated and provided a surprising wealth of exciting data. The Johnstone Plasma Analyser detected the first presence of cometary ions 600,000 km from the nucleus at 12 hours before the closest approach. The Dust Impact Detectors reported the first impact of a fairly large particle at 15:30:56. Bow shocks/waves and acceleration regions were also detected. On 23 July 1992 Giotto operations were officially terminated after completion of final orbit adjustments and configuration of the spacecraft for its third hibernation. Only 1 to 7 kg of fuel is left on board, insufficient for any extensive future maneuvers. Giotto flew by the Earth on 1 July 1999 at a closest approach of about 219,000 km at approximately 02:40 UT (10:40 p.m. EDT, 30 June).

The spacecraft was moving at about 3.5 km/sec relative to Earth. Spacecraft image for illustrative purposes - not necessarily in the public domain. Alternate Names Giotto overview / Space Science / Our Activities / ESA Giotto had a number of very impressive ‘firsts’ and achievements to its credit: It was Europe's first deep-space mission. It photographed the first close-up images of a comet nucleus (Halley). It discovered the size and shape of Halley's nucleus and discovered that the surface is very dark and that bright jets of gas and dust spring out of its nucleus. It was the first deep-space mission to change orbit by returning to Earth for a gravity-assist manoeuvre. Giotto made the closest comet fly-by to date by any spacecraft (about 200 kilometres from Comet Grigg-Skjellerup) and studied the interaction between the solar wind, the interplanetary magnetic field, and the comet itself. It was the first spacecraft to encounter two comets and in doing so measured the size, composition, and velocity of dust particles and measured the composition of those two comets.

Spacecraft Giotto was based on the GEOS Earth-orbiting research satellites, which were built by British Aerospace at Bristol, United Kingdom. The most significant modification was the addition of a shield to protect it from a battering by high-speed dust particles during the comet encounter. By spacecraft standards, the 960-kilogram Giotto was small in size. Its main body was a short cylinder about 2 metres in diameter by about 1 metre in height. It contained three interior platforms: the top platform, a main platform, and an experiment platform. Each of these consisted of a disc within the cylinder on which were mounted various subsystems and science experiments. On top of the cylinder was a 1.5-metre diameter high-gain dish antenna and gave the spacecraft a total height of about 3 metres. The main rocket motor was positioned in the centre of the cylinder with the nozzle protruding from the bottom.

The most difficult problem to overcome was how to ensure that Giotto survived long enough to snap its close-up pictures of the nucleus when the spacecraft and the comet were heading towards each other at a combined speed of 245 000 kilometres per hour (equivalent to crossing the Atlantic Ocean in 11 minutes!). At this speed, a 0.1 gram dust particle would be able to penetrate 8 centimetres of solid aluminium. Since it was out of the question to equip Giotto with a 600-kilogram aluminium shield, engineers turned to a more subtle, sandwich design first proposed by American astronomer Fred Whipple back in 1947 — long before the beginning of the Space Age. The spacecraft's dust shield consisted of two protective sheets, 23 centimetres apart. At the front was a sheet of aluminium (1 millimetre thick), which would vaporise all but the largest of the incoming dust particles. A 12-milimetre thick sheet of Kevlar at the rear would absorb any debris that pierced the front barrier. Together they could withstand impacts from particles up to 1 gram in mass and travelling 50 times faster than a bullet.

Electrical power came from a solar array made of about 5000 silicon cells wrapped around Giotto’s cylindrical exterior. These provided 190 Watts of power during the first comet encounter. Four silver-cadmium batteries were carried as back up and for use when the spacecraft was in shadow. The spacecraft was spin-stabilised as it rotated at 15 revolutions per minute. During the encounter with Halley’s Comet, the spacecraft approached with its dust shield and spin axis pointing towards the nucleus. Its dish antenna continually pointed at the Earth to ensure non-stop communications. Journey Giotto was initially injected into a geostationary transfer orbit. After three revolutions around the Earth, the on-board motor was fired to inject into an interplanetary orbit. After a cruise phase of 8 months, Giotto encountered Comet Halley on 14 March 1986. For its (initially unscheduled) visit to the second comet, Grigg-Skjellerup, Giotto was flown back to the direction of Earth for a gravity-assist to reach its new target. To add more detail, the adventure began with Giotto almost 150 million kilometres from Earth.

On 12 March 1986, the spacecraft's instruments first detected hydrogen ions 7.8 million kilometres from Comet Halley. 22 hours later, Giotto crossed the bow shock of the solar wind (the region where a shock wave is created as the supersonic solar particles slow to subsonic speed) and entered the densest part of the dusty coma. At this point, the camera was switched to tracking mode to follow the brightest object (the comet nucleus) in its field of view and began to send the first, fuzzy images back to Earth. Excitement rose at the European Space Operations Centre in Darmstadt, Germany, as the stream of pictures and data came in. Located in adjacent rooms, each of the ten experiment teams scrutinised the latest information and struggled to come up with a preliminary analysis. The first of 12 000 dust impacts were recorded 122 minutes before closest approach. Images were transmitted as Giotto closed in to within a distance of 1372 kilometres, but the rate of dust impacts rose sharply as the spacecraft passed through a jet of material that streamed away from the nucleus.

At that time the spacecraft was travelling at a speed of 68 kilometres a second relative to the nucleus of Halley. Only 7.6 seconds before closest approach, the spacecraft was sent spinning by an impact from a ‘large’ (one gram) particle. Monitor screens went blank as contact with the Earth was temporarily lost. TV audiences and anxious Giotto team members feared the worst, but, to everyone’s amazement, occasional bursts of information began to come through. Giotto was still alive. Over the next 32 minutes, the sturdy spacecraft's thrusters stabilised its motion and contact was fully restored. By then Giotto had passed within 596 kilometres of the nucleus and was heading back into interplanetary space. The remarkably resilient little spacecraft continued to return scientific data for another 24 hours on the outward journey. The last dust impact was detected 49 minutes after closest approach. The historic encounter ended 15 March when Giotto’s experiments were turned off. However, the spacecraft still had 60 kilograms of fuel available, so the option was open to continue Giotto’s voyage of exploration.

A series of three small orbital corrections ensured that it would return to Earth almost exactly five years after launch. On 2 April 1986, the spacecraft was placed into hibernation in the hope that it could be successfully revived and dispatched on another mission. 1419 days later, in February 1990, the signal was sent to reawaken Giotto. After such a long period without contact, controllers had no idea whether the harsh environment of space had damaged its systems. Another unknown was the direction in which the main antenna was pointing. The only hope was that an omni-directional low-gain antenna would detect the wake-up signal. Two hours later, a weak answer from Giotto was received at the NASA Deep Space Network ground station near Madrid, Spain. Within a week, full control was regained and the ESA team was able to assess its condition. Three science instruments proved fully operational, while four more were partially damaged but usable. Although the remaining three instruments, including the camera, were disabled, it was decided to redirect the spacecraft towards a second comet.

On 2 July 1990, Giotto's orbit was altered as it flew past the Earth, just 22 730 kilometres above the cloud tops. This was the first time a spacecraft coming from deep space had used the Earth for a gravity-assist. During the fly-by, observations were made of the Earth’s magnetic field and energetic particle environment. After another prolonged hibernation, Giotto's payload was switched on in the evening of 9 July 1992. The Grigg-Skjellerup fly-by took place the following day, about 215 million kilometres from Earth. Giotto crossed the bow shock and entered the dust coma about 17 000 kilometres from the comet. Aimed directly at the nucleus, Giotto missed by a mere 100 to 200 kilometres — the closest ever cometary fly-by. History Giotto was originally put forward as part of a joint NASA/ESA comet mission, but at a later stage the United States pulled out. Then ESA took the bold decision to proceed alone on this once-in-a-lifetime venture.

There was little leeway for delays if this fly-by opportunity was missed, Halley's Comet would disappear into the depths of the Solar System, to be hidden from view for the next 75 years! Giotto was ESA's first deep space mission, part of an ambitious international effort to solve the mysteries surrounding Comet Halley. The plan was to send an armada of five space probes — two Soviet, two Japanese and one European — towards the comet on its return to the inner Solar System in 1986. While the Japanese spacecraft made long distance measurements, the Soviet Vegas would act as pathfinders, passing close enough to locate the comet's nucleus. The information they sent back would allow Giotto to home in with great accuracy on Halley's solid heart. After the mission was given the go-ahead by ESA in 1980, it was put together very quickly. Originally envisaged as part of a dual launch by a powerful Ariane 3 rocket, it was eventually launched by an Ariane 1 rocket (flight V14) on 2 July 1985.

Partnerships The following organisations built the various scientific instruments on board Giotto: University of Cologne (Germany), MPI (Lindau, Germany), University of Kent (Canterbury, United Kingdom), CESR (Toulouse, France), Mullard Space Science Laboratory (Holmbury St Mary, United Kingdom), MPI (Heidelberg, Germany), CNRS (Verrières-le-Buisson, France), St. Patrick's College (Maynooth, Ireland), University of Bern (Switzerland) and the Ruhr University (Bochum, Germany). Last update: 13 August 2013 More about...

Giotto Giotto Mar 13, 1986 - Comet Halley Flyby Jul 02, 1990 - Earth Flyby Jul 10, 1992 - Comet Grigg-Skjellerup Flyby Jul 01, 1999 - Earth Flyby End of Mission First closeup images of a comet nucleus First European deep space mission First spacecraft to encounter two comets First spacecraft returning from deep space to use Earth gravity assist The spacecraft Giotto was named after artist Giotto di Bondone, who had used the appearance of Comet Halley in 1301 as the model for the Star of Bethlehem in his 1304 painting titled "Adoration of the Magi". The purpose of the Giotto mission was to study Comet Halley during the comet's perihelion passage in 1986. Giotto also encountered Comet Grigg-Skjellerup during an extended mission in 1992.

The major objectives of the mission were: Obtain the first closeup images of a nucleus of a comet Determine the elemental and isotopic composition of volatile components in the cometary coma, particularly parent molecules Characterize the physical and chemical processes that occur in the cometary atmosphere and ionosphere Determine the elemental and isotopic composition of dust particles Measure the total gas-production rate and dust flux and size/mass distribution and derive the dust-to-gas ratio Investigate the macroscopic systems of plasma flows resulting from the cometary-solar wind interaction Giotto was launched on an Ariane-1 rocket by the European Space Agency (ESA) on July 2 1985. The spacecraft design was based on the GEOS research satellites, and a 600kg shield had to be added to ensure it would survive a close comet encounter. Giotto carried 10 instruments which included a multicolor camera, mass spectrometers, dust impact detector, plasma instruments, energetic particle analyzer, and a magnetometer. The power source was a 5,032 cell solar array that provided 190 watts of power during the first comet encounter, and four silver-cadmium batteries was carried along as well.

On March 13, 1986, Giotto approached Comet Halley for a targeted 500 km flyby. The spacecraft crossed the bow shock of the solar wind, and into the comet's coma. At this point the camera was switched to tracking mode to follow the brightest object (the comet nucleus) in its field of view and was returning images back to Earth. The images revealed the comet nucleus to be a dark peanut-shaped body with two bright jets spewing material out. The dust impacts were lower than expected until a few minutes prior to closest approach when the impact rate rose sharply, as the spacecraft apparently crossed into the path of one of the jets. Just 14 seconds prior to closest approach, the spacecraft was struck by a large dust particle which knocked the spacecraft off Earth point, and it took approximately 30 minutes for the spacecraft to recover and point its antenna back to Earth and reestablish communications. Passing by the comet at a velocity of 68 km/second, the spacecraft had suffered some damage. Some of the instruments no longer worked or were partially functional. The star mapper's baffle was peppered with holes. Subsequent analysis of Giotto's data showed a new wealth of data collected.

Water accounted for about 80% by volume of all of the material being thrown out by the comet. Seven jets were identifed which threw out 3 tons/sec of material. The largest grain detected was 40mg, though the large particle that hit the spacecraft was estimated to be from 0.1 to 1 gram. The data from the plasma and ion mass spectrometer instruments indicated that the surface of Comet Halley is covered in a layer of organic material. The actual closest approach was measured at 596 km. On April 2, 1986, Giotto was placed into hibernation. In April 1990, Giotto was reactivated. Three of the instruments proved fully operational, four partially damaged but usable, and the remainder, including the camera, were unusable. On July 2, 1990, Giotto made a close encounter with Earth and was retargeted to a flyby of Comet Grigg-Skjellerup on July 10, 1992. Aimed directly at the comet, Giotto missed the comet by 200 km in the closest ever flyby of a comet.

Flying by at 14 km/second (as opposed to 68 km/sec for Halley), and with a dust production rate about 1/200 of Halley's, the Comet Grigg-Skjellerup encounter was expected to have very little dust damage to the spacecraft. After the 1992 comet encounter, Giotto was placed into an Earth-return orbit using almost all remaining fuel. The satellite was put back into hibernation on July 23, 1992 and the Giotto mission officially terminated. In its present orbit, Giotto will pass silently within 300,000 km of the Earth on July 1, 1999 (best estimate 220,000) : no satellite operations are planned.

Ron Baalke, STARDUST Webmaster, ron@jpl.nasa.gov Last Updated Giotto Information Launch Date: 02 July 1985 Launch Vehicle: Ariane Planned on-orbit mass: 582.7 kg Power System: Solar cell array of 196 W The Giotto mission was designed to study Comet P/Halley, and also studied Comet P/Grigg-Skjellerup during its extended mission. The image at the top of the page is the nucleus of Halley taken by Giotto. The major objectives of the mission were to: (1) obtain color photographs of the nucleus; (2) determine the elemental and isotopic composition of volatile components in the cometary coma, particularly parent molecules; (3) characterize the physical and chemical processes that occur in the cometary atmosphere and ionosphere; (4) determine the elemental and isotopic composition of dust particles; (5) measure the total gas-production rate and dust flux and size/mass distribution and derive the dust-to-gas ratio; and, (6) investigate the macroscopic systems of plasma flows resulting from the cometary-solar wind interaction.

The spacecraft encountered Halley on March 13, 1986, at a distance of 0.89 AU from the sun and 0.98 AU from the Earth and an angle of 107 degrees from the comet-sun line. The goal was to come within 500 km of Halley's comet at closest encounter. The actual closest approach was measured at 596 km. The spacecraft had a dust shield consisting of a front sheet of aluminum (1 mm thick) and a 12 mm Kevlar near sheet separated by 25 cm, which could withstand impacts of particles up to 0.1 g. The scientific payload was comprised of ten hardware experiments: a narrow-angle camera, three mass spectrometers for neutrals, ions and dust, various dust detectors, a photopolarimeter and a set of plasma experiments. All experiments performed well and returned a wealth of new scientific results, of which perhaps the most important was the clear identification of the cometary nucleus. Fourteen seconds before closest approach, Giotto was hit by a "large" dust particle. The impact caused the spacecraft angular momentum vector to shift 0.9 degrees.

Scientific data were received intermittently for the next 32 minutes. Some experiment sensors suffered damage during this 32-minute interval. Other experiments (the camera baffle and deflecting mirror, the dust detector sensors on the front sheet of the bumper shield, and most experiment apertures) were exposed to dust particles regardless of the accident and also suffered damage. Many of the sensors survived the encounter with little or no damage. Questionable or partially damaged sensors included the camera (later proved to not be functional) and one of the plasma analyzers (RPA). Inoperable experiments included the neutral and ion mass spectrometers and one sensor each on the dust detector and the other plasma analyzer (JPA). During the Giotto extended mission, the spacecraft successfully encountered Comet P/Grigg-Skjellerup on July 10, 1992. The closest approach was approximately 200 km. The heliocentric distance of the spacecraft was 1.01 AU, and the geocentric distance, 1.43 AU at the time of the encounter. The payload was switched-on in the evening of July 9. Eight experiments were operated and provided a surprising wealth of exciting data.

The Johnstone Plasma Analyser detected the first presence of cometary ions 600,000 km from the nucleus at 12 hours before the closest approach. The Dust Impact Detectors reported the first impact of a fairly large particle at 15:30:56. Bow shocks/waves and acceleration regions were also detected. After the P/Grigg-Skjellerup encounter operation were terminated on 23 July 1992. Giotto flew by the Earth on 1 July 1999 at a closest approach of about 219,000 km at approximately 02:40 UT (10:40 p.m. EDT, 30 June). The spacecraft was moving at about 3.5 km/sec relative to Earth. Giotto's children: where are they now? / ESA history / Welcome to ESA / About Us / ESA Giotto 30 years - children's art Giotto's children: where are they now? 11 March 2016 Thirty years ago, ESA’s first deep space mission Giotto met with Comet Halley and inspired an art competition for children.

Giotto was designed to help solve the mysteries surrounding Comet Halley by passing as close as possible to the comet's nucleus, which it achieved on the night of 13–14 March 1986. The Giotto probe swept within 600 km of Comet Halley, obtaining the first close-up images of a comet. At the time, we invited children aged ten years and under from all Member States to send in their drawings inspired by the encounter. Giotto 30 years - children's art Where are they now? Halley’s comet (more correctly known as Comet 1P/Halley) is one of the most famous comets in history. Its close approaches every 75–76 years have clearly visible from Earth and much recorded. At the time of the 1986 encounter, Prof. Roger Bonnet, then Director of the ESA’s Scientific Programme, who conceived the idea, explained: “At the time of its next closest approach to the Sun in 2061, those 10 year olds will be in be in their mid-eighties and most likely still alive to witness it.

“There will undoubtedly be a very big celebration at this next perihelion and most likely new space missions in orbit to watch the comet 75 years after Giotto. The idea was to invite these ‘children’ to celebrate the event with interviews and photos in front of the paintings they had sent in 75 years before.” ESA received 25 paintings and on 15 June 1986 all the participants, together with their parents, were welcomed at ESA Headquarters in Paris by the then Director General Prof. Reimar Lüst, together with Prof. Bonnet, who presented them a diploma and a small model of the Giotto spacecraft. At the end of the ceremony, the children were invited back to ESA again in 2061. Giotto 30 years - children's art Rather than waiting until 2061, we invite any of the original contest participants to get in touch with us to receive a memento from ESA’s Rosetta mission and its more recent comet landing. You can contact us via connectwithus@esa.int or via @esa on Twitter mentioning #Giotto30 .

Following in Giotto's footsteps, Rosetta has been studying Comet 67P/Churyumov-Gerasimenko for nearly two years. Rosetta was the first spacecraft to go into orbit around a comet in August 2014, and its Philae probe made the historic landing on 12 November 2014. In September of this year, the Rosetta orbiter will make its own controlled landing on the comet’s surface with all instruments active to get as much data possible after observing the complete cycle of a comet in our Solar System. The full set of Giotto-inspired drawings sent in 1986 can be seen here Comet Halley's nucleus as seen by Giotto About Giotto Launched on 2 July 1985 on an Ariane 1 rocket, Giotto was part of an ambitious international effort to solve the mysteries surrounding Comet Halley. It was also the first deep-space mission to change orbit by returning to Earth from an interplanetary trajectory for a gravity-assist.

Rate this Giotto to Halley's comet | DeepDyve Try 2 weeks free now Giotto to Halley's comet Schwehm, Gerhard; Pedersen, Arne On July 2, 1985, 11:23 UTC (Universal Time Coordinated), the Giotto spacecraft, the European Space Agency (ESA) contribution to the international effort to study Halley's comet in situ, was successfully launched. The spacecraft was placed by an Ariane I launcher into a geostationary transfer orbit (GTO). About 32 h later, on July 3, 1985, 19:24 UTC, during its fourth perigee passage, the built-in solid propellant transfer propulsion system (TPS) was fired, and Giotto was injected into its escape trajectory from the earth's gravitational influence in order to encounter the comet on March 13, 1986. The TPS firing was so precise that even without further orbit correction maneuvers, Giotto would miss the comet by only 50,000 km.

On July 6, 1985, the high-gain antenna was despun, i.e., set rotating in the opposite sense relative to Giotto's spin so that it maintains a constant direction toward the earth. The spacecraft spin rate was set to the nominal 15 rpm. Experiment switch on is scheduled for September 2, 1985, onward, in time for the Comet Giacobini-Zinner encounter of the National Aeronautics and Space Administration's International Cometary Explorer spacecraft. Giotto carries 10 experiments for the study of Halley's comet. They will provide images of the nucleus, examine the chemistry of the coma gases, analyze the comet's phsma, and investigate the dust particles in the environment of the comet. Giotto will provide the Cover. An example of a three-dimensional network of fractures in rock which has been idealized as intersecting discs randomly located in space. Such random networks can be generated by using statistical distributions of fracture density, orientation, radius, hydraulic aperture, and spatial correlations that are estimated through field investigations. A model to analyze fluid flow through such networks has been developed in order to study.how fracture geometry controls flow through rock masses.

The disc model is the first and simplest of a series of three-dimen' sional fracture hydrology models under development at Lawrence Berkeley Laboratory. Each of the succeeding models will include more of the complexities evidenced in real fractures, such as arbitrary fracture shape, channeling within the fractures, and interactions with the matrix rock. This new approach to fluid flow in fractured rock is supported by the U.S. Department of Energy under contract number DE-AC03-76SF00098. The illustration is from "A model for steady fluid flow in random three-dimensional networks of disc-shaped fractures," by Jane Long, Peggy Gilmour, and Paul Witherspoon, Water Resources Research, 21, p. 1105, 1985 (original drawing by Marilee Bailey). most detailed observations of Halley's comet because it will pass closer to the comet than any other spacecraft. The nominal encounter distance will be 500 km on the sunward side of the nucleus.

T o achieve t h ~ s goal, an agreement has been reached wiLh the Soviet Intercosmos Space Agency to use the two VEGA spacecraft (which will pass the comet on March 6 and 9, 1986) as pathfinders to improve the knowledge of the comet's orbit. The satellite will start transmitting scientific data 4 h prior to encounter. The data will be received by the 64-m Parkes Radio Telescope dish at Parkes, Australia, and transmitted in real time to the European Space Operations Centre (ESOC), Darmstadt, Federal Republic of Germany, where they can be analyzed by the experimenters. This news item wcls contributed by Gerhard Schwehm and Arne Pedersen, European Space Agency, Neuilly, France. Controversy Over Mass Extinctions PAGE 593 The notion that mass extinctions of species occur at 26-million-year (m.y.) intervals received wide attention in the scientific and popular press a little over a year ago. According to the theory, some sort of periodic extraterrestrial event had led to the episodes of extinction; comet showers brought on by any of a variety of causes were frequently offered as one explanation.

Now the idea is back in the news, this time drawing criticism. An article published in the the June 20 issue of Nature cr~ticizes original analysis, by David Raup and John Sepkoski of the University of Chicago, on the grounds that their data base was overly pared down and that they used a biased definition for mass extinction. Raup and his supporters say that papers now in press will answer the objections. According to Antoni Hoffman of the Lamont-Doherty Geological Observatory of Columbia University, Palisades, N. Y., Raup and Sepkoski designated as an extinction peak any stage with more extinctions than the stages that precede and follow it. This means that on the average every fourth stage must be considered a "peak," and since the average stage duration was 6.2 m y . , the peaks could have been expected to come up with the 26m.y. periodicity.

Hoffman went on to say that Raup and Sepkoski excluded "extant families and families with imprecise or questionable stratigraphical ranges" from their totals in order to remove the "noise and pull of the Recent [epoch]." As a result, the extinction of 10 families during a stage of the Cenozoic era is considered a mass extinction and is compared to the extinction of hundreds of families in a stage of the Paleozoic era. Also, Hoffman said, had Raup and Sepkoski considered a slightly wider time range, then the 26-m.y. periodicity would not have held up under a criterion developed by Raup but not used in his paper. Hoffman suggested that the results This page may be freely copied. also might have been different had Raup and Sepkoski used a different time scale, without the assumption that stratigraphical stages are equal in length. Raup told Eos that he and Sepkoski "have manuscripts in press or submitted [that]. . .will take care of [Hoffman's objections]." One paper from a symposium has been in press for 2 years.

They have now analyzed the data for extinction of genera rather than families and, in addition, have used narrower time intervals than in their original analysis; the results are "very nicely confirmatory," according to Raup. Walter Alvarez of the University of California, Berkeley, commented, "At this time in the development of the whole field, further detailed statistical analyses of Raup and Seposki's data such as [Hoffman's] are not going to solve the problem one way or another." Alvarez identified a 28-m.y. periodicity in ancient craters that added weight to Raup and Sepkoski's argument. The important thing, he told Eos, is to examine the results of the improved data base. Alvarez was among those who proposed in 1980 that the demise of the dinosaurs resulted from a massive meteorite impact (Eos, April 22, 1980, p. 259). Michael Rampino of the Goddard Institute for Space Studies in New York, N.

Y., said he and others have "already done the kinds of things that Hoffman is saying we should do." Even with the use of different time scales or scatter in the dates, a 26- to 30-m.y. periodicity remains that is "quite robust." Rampino and a colleague had proposed that a 30-m.y. periodicity in extinctions could be brought on when the solar system passes through the plane of the Milky Way. Have mass extinctions occurred at regular intervals? "Views tend to be rather polarized," commented Raup, who said that he believes that people resist the idea that the cosmic (e.g., showers of comets) can become so entwined with the terrestrial (e.g., the extinction of species). Whether the objections are emotional or rational, the issue is bound to remain cloudy for some time to come.-JAK Geophysicists PAGE 593 Richard A. F. Grieve was recently awarded a Doctor of Science degree from his alma mater, Aberdeen University in Scotland. The degree is the highest conferred by British universities and was given in recognition of his contributions to the study of impact cratering phenomena as geologic processes.

Grieve is a research scientist at the Earth Physics Branch of Canada's Department of Energy, Mines, and Resources and is secretary of the International Union of Geological Sciences' Commission on Comparative Planetology. George A. Kolstad has received a "Sustained Superior Performance Cash Award" from the Department of Energy (DOE) for his efforts on behalf of the geosciences, especially in the area of continental scientific drilling. Kolstad is head of the geosciences program in the division of engineering and geosciences at DOE. Eos Transactions Wiley Loading next page... ESA Science & Technology: Giotto Terms and Conditions ESA's first deep space mission, Giotto was designed to help solve the mysteries surrounding Comet Halley by passing as close as possible to the comet's nucleus, which it achieved on 13 March 1986. No-one expected the spacecraft to survive its battering from comet dust during this encounter, but although Giotto was damaged during the flyby, most of its instruments remained operational. The mission was extended to allow an unprecedented encounter with a second comet, Grigg-Skjellerup.

Latest News ESA remembers the night of the comet 11 March 2011 Twenty-five years ago, ESA made its mark in deep space. A small spacecraft swept to within 600 km of Halley's comet. The Giotto probe was nearly destroyed by the encounter but what it saw changed our picture of comets forever. Read more Shortcut URL

Question: What was the Giotto spacecraft sent to investigate in 1985?
Answer: Halley's comet