P725 CEEFAX 725 Sun 22 Dec 16:47/15 1/11 HALLEY GIOTTO SPACECRAFT - Adoration of Magi Giotto Ambrogio di Bondonj (1266-1337) was a Florentine painter who worked on a series of frescoes on the Cappjlla dell' Arena in Padua. One of the 38 scenes, The Adoration of the Magi, showed the Star of Bethlehem in the form of a comet. He painted this in 1303, two years after Halley's comet appeared. The European Space Agency's Giotto spacecraft is named after this painter, but it will bj taking a far more analytical look at Halley's comet. Free telescope view 724s10 MoreP725 CEEFAX 725 Sun 22 Dec 16:41/27 2/11 HALLEY GIOTTO SPACECRAFT - Arianj cargo The European Space Agency's Giotto spacecraft is djsignjd to study Comet Halley in impressive detail. It was launched on the Ariane rocket from Kourou in French Guyana on July 2 and will rendezvous with the comet for about four hours on March 13-14. During that time, a wealth of scientific detail will be collected by cameras and monitoring devices and sent back to Earth before the dust in the comet's tail is expected to destroy the spacecraft. MoreP725 CEEFAX 725 Sun 22 Dec 16:21/51 3/11 HALLEY GIOTTO SPACECRAFT - unlike the othjts Giotto is one of five spacecraft to study Comet Halley, but it is the most ambitious and sophisticated. Probes from the Soviet Union are called Vega 1 and Vega 2, and those from Japan are the MS-T5 and Planet-A. Unlike the others, Giotto is designed to pass through the dust and gas of the comet, and although it has several protective lazjrs, there is a risk of damage to the instruments before its likely disintegration sometime during the four-hour encounter. MoreP725 CEEFAX 725 Sun 22 Dec 16:57/52 4/11 HALLEY GIOTTO SPACECRAFT - Britain's part There are 10 experiments on board Giotto, two of which have been co-ordinated bz British scientists. The 10 experiments are intended to take pictures of the comet's nucleus, examine the coma's chemistry, and analysj the plasma and the dust particles around the comet. The two British-led experiments are concerned with the composition and distribution of positive ions and with the distribution and properties of dust particles. MoreP725 CEEFAX 725 Sun 22 Dec 16:51/47 5/11 HALLEY GIOTTO SPACECRAFT - ions and EPA One British-directed experiment is the Johnstonj Plasma Analyses, co-ordinated bz the Mullard Space Science Laboratory of University College London. The EPA will investigate the formation of the plasma tail of the comet bz measuring the energy and mass distributions of positively-charged ions near the comet. A sensor will observe the solar wind ions as they interact with the ions from the comet. Scientists from around the world have contributed to the EPA. MoreP725 CEEFAX 725 Sun 22 Dec 16:32/12 6/11 HALLEY GIOTTO SPACECRAFT - measuring dust The other British-led experiment aboard Giotto is DIDSY - the Dust Impact Detection System. The study, which is co-ordinated bz scientists at the University of Kent, will measure the mass of dust particles hitting Giotto's protective shield as it approaches the coma and tail. All the protective shield is used as an extremely sensitive dust detector. More dust is expected closer to the comet, and it is thjsj particles which are expected to eventually destroy Giotto. MoreP725 CEEFAX 725 Sun 22 Dec 16:45/12 7/11 HALLEY GIOTTO SPACECRAFT - rehearsals success The first rehearsals for Giotto's encounter with Halley were held in mid-October. Both the spacecraft and its payload were tested and all systems worked. They were first of a series of "dry runs" before the final "dress rehearsal" a few days before it meets Halley on March 13-14. CEEFAX will report on the preliminary findings of Giotto's mission, even though this special comet section will have been dropped bz then. MoreP725 CEEFAX 725 Sun 22 Dec 16:09/28 8/11 HALLEY ICE AND THE SNOWBALL - unexpected data Halley's comet is being closely studied bz scientists around the world, but important evidence about the make-up of comets was gathered earlier in 1985. A US spacecraft, the International Cometary Explorer (ICE) cut through the tail of the Giacobini-Zinnjr comet on July 11 - the first spacecraft to fly through a comet's tail. The data sent back to earth sjemjd to confirm the theory that comets are like bdirty snowballs", but there was some unexpected evidence on other matters. MoreP725 CEEFAX 725 Sun 22 Dec 16:14/38 9/11 HALLEY ICE AND THE SNOWBALL - theory supported The ICE spacecraft detected a large amount of charged water and carbon monoxide particles, and some tiny dust particles in Giacobini-Zinner's tail. This would support the theory that the nucleus of the comet is made of ice, silicate minerals and possibly metals, ICE scientists in the US say. ICE flew within 4,900 miles of the comet on September 11, 1985. (The European Space Agency's Giotto space- craft is expected to pass Halley's comet within only a few hundred miles). MoreP725 CEEFAX 725 Sun 22 Dec 16:12/01 10/11 HALLEY ICE AND THE SNOWBALL - no bow wave? An unexpected finding bz the ICE space- craft when it encountered the Giacobini -Zinnjr comet was the interaction of the solar wind and the comet. The data sent back showed such inter- action was far more complicated and turbulent than thought. It had been assumed that the speeding comet would send out a "bow wave" like a ship in the water. Instruments aboard ICE detected a large area of magnetic and particle turbulence, but no clear "bow wave". MoreP725 CEEFAX 725 Sun 22 Dec 16:40/02 W=,,4<,,4<,,,lh,,lh,,,4 11/11 HALLEY ICE AND THE SNOWBALL - not much dust Scientists had also expected ICE to pick up evidence of much more dust - it detected dust particles at a rate of only about one per second. The ICE spacecraft detected water in Giacobini-Zinnjr comet at the same time that an Earth-orbiting satellite, the International Ultraviolet Explore , found water in the approaching Halley's comet. It is quite possible the general data returned by Giotto from Halley's comet will bj similar to that of ICE's. Comet special index 720 More