- Email: [email protected]
Giotto on its way to Halley's Comet
discoveries seem to be made on a weekly basis. Stars which have consumed their nuclear fuel - hydrogen and helium - can end their lives in a spectacular explosion, a supernova. The Exosat telescopes have provided detailed images of the remnants of these dead stars which have enabled astronomers to deduce the amount of energy involved in the original explosion and the physical conditions in space in the neighbourhood of the explosion. Some exploded supernovae might end as neutron stars or as “black holes”. Astronomers have been able to study a number of these “exotic” objects in the Milky Way. These objects, heavier than the Sun but very much smaller, have enormous gravitational fields and radiate many thousands of times more energy. Exosat has also probed deeper into space, outside our own galaxy, to study the energy output of active galaxies, quasars and clusters of galaxies which in many cases emit far more energy than our own galaxy. In fact, in one of these galaxies (the Seyfert Galaxy, NGC 4051), Exosat has discovered regular X-ray fluctuations which may well be due to the presence of very hot material orbiting around a massive black hole, with a mass millions of times greater than that of our own Sun, at the very centre of the galaxy. The Exosat mission, now in its third year, will continue its observations by building on the discoveries made during the first two years in orbit. Exosat has provided Europe with the means to be a major force in X-ray astrophysics for the rest of the decade. Based on the success of this mission, ESA has chosen, as one of the cornerstones of its long-term scientific programme, a new cosmic X-ray spectroscopy mission which it is hoped will take European astrophysics into the 21st century.
2.3. GlOllO
ON ITS WAY TO HALLEY’S COMET@J
At 11.23 h 13 s GMT on 2 July 1985, Giotto, ESA’s interplanetary space probe which will encounter Halley’s Comet on 13 March 1986, was successfully launched by an Ariane 1 launcher into geostationary transfer orbit (apogee 35 966 km for 35 912 km intended; perigee 199.2 km for 200 km intended; inclination 7”) from the Ariane launch site at Kourou, French Guiana. Following separation from the third stage of the launcher, ESA’s Space Operations Centre (ESOC, at Darmstadtc4), FRG) took over control of the spacecraft 22 minutes after lift-off. After three revolutions in its transfer orbit, the European Space Agency’s interplanetary space probe Giotto has successfully been injected at 19 h 24 m GMT on Wednesday, 3 July 1985 into T’)ESA News Release No. 18 of 2 July 1985 and ESA News Release No. 20 of 4 July 1985. cJ)ESOC is in charge of all satellite operations and the corresponding ground facilities and communications networks. The ESOC-controlled network includes a central control centre in Darmstadt and telemetry tracking and control facilities at ground stations around the world.
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an Earth-escape trajectory on its way to the comet after the voyage of 700 million kilometres. The manoeuvre has been conducted from the ESA Operations Control Centre (ESOC) in Darmstadt, FRG, via the ESA ground station network, and Giotto is now on its way to encounter Halley’s Comet in March 1986. Giotto will not be alone in investigating Halley, but will form part of a truly international effort involving two USSR spacecraft, Vega 1 and 2, launched on 15 and 21 December 1984 respectively, two Japanese spacecraft, Sakigake launched on 8 January 1985 and Planet A scheduled for launch in August 1985, and the NASA International Comet Explorer, ICE (formerly ISEE-3), launched on 22 December 1983, which has been diverted from its previous Earth-orbiting position for an encounter with Halley. The various Halley’s encounters are scheduled for 1 March (Sakigake), 6 March (Vega l), 8 March (Planet A), 9 March (Vega 2) 13 March (Giotto) and 28 March (ICE), and the various spacecraft will be at distances from Halley’s nucleus ranging from seven million kilometres (Sakigake) to a mere 500 kilometres (Giotto).
2.4. DISCOVERY OF VERY FAST R
Early last year astronomers came up with a proposal to use the European Space Agency’s X-ray Observatory Satellite, Exosat in order to search for very fast rotating neutron stars in X-ray binaries. The observations since made have led to the discovery of a completely unexpected phenomenon, that of quasi-periodic oscillations, which may indicate the presence of fast-rotating neutron stars in very old X-ray binary systems. The discovery of these oscillations, which was made public in July 1985, has opened up a whole new road of investigation into the bizarre world of neutron stars, a world in which, because of its extreme gravitational conditions, it will be possible to test some of the fundamental laws of physics to their limits.
2.5. ASSERTIONS BY US COMPANIES AGAINST ARIANE COMMERCIAL LAUNCH POUCIES6
On 17 July 1985, the President of the United States signed a decision relieving the European Space Agency and its Member States from any further investigation or action under Section 301(a) of the US Trade Act of 1984 as amended (19 USC 24 11(a)), a statute aimed at protecting US foreign trade interests. c5’ESA News Release No. 21 of 19 July 1985. @)ESA News Release No. 22 of 24 July 1985.
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2.3. GlOllO
ON ITS WAY TO HALLEY’S COMET@J
At 11.23 h 13 s GMT on 2 July 1985, Giotto, ESA’s interplanetary space probe which will encounter Halley’s Comet on 13 March 1986, was successfully launched by an Ariane 1 launcher into geostationary transfer orbit (apogee 35 966 km for 35 912 km intended; perigee 199.2 km for 200 km intended; inclination 7”) from the Ariane launch site at Kourou, French Guiana. Following separation from the third stage of the launcher, ESA’s Space Operations Centre (ESOC, at Darmstadtc4), FRG) took over control of the spacecraft 22 minutes after lift-off. After three revolutions in its transfer orbit, the European Space Agency’s interplanetary space probe Giotto has successfully been injected at 19 h 24 m GMT on Wednesday, 3 July 1985 into T’)ESA News Release No. 18 of 2 July 1985 and ESA News Release No. 20 of 4 July 1985. cJ)ESOC is in charge of all satellite operations and the corresponding ground facilities and communications networks. The ESOC-controlled network includes a central control centre in Darmstadt and telemetry tracking and control facilities at ground stations around the world.
33
an Earth-escape trajectory on its way to the comet after the voyage of 700 million kilometres. The manoeuvre has been conducted from the ESA Operations Control Centre (ESOC) in Darmstadt, FRG, via the ESA ground station network, and Giotto is now on its way to encounter Halley’s Comet in March 1986. Giotto will not be alone in investigating Halley, but will form part of a truly international effort involving two USSR spacecraft, Vega 1 and 2, launched on 15 and 21 December 1984 respectively, two Japanese spacecraft, Sakigake launched on 8 January 1985 and Planet A scheduled for launch in August 1985, and the NASA International Comet Explorer, ICE (formerly ISEE-3), launched on 22 December 1983, which has been diverted from its previous Earth-orbiting position for an encounter with Halley. The various Halley’s encounters are scheduled for 1 March (Sakigake), 6 March (Vega l), 8 March (Planet A), 9 March (Vega 2) 13 March (Giotto) and 28 March (ICE), and the various spacecraft will be at distances from Halley’s nucleus ranging from seven million kilometres (Sakigake) to a mere 500 kilometres (Giotto).
2.4. DISCOVERY OF VERY FAST R
Early last year astronomers came up with a proposal to use the European Space Agency’s X-ray Observatory Satellite, Exosat in order to search for very fast rotating neutron stars in X-ray binaries. The observations since made have led to the discovery of a completely unexpected phenomenon, that of quasi-periodic oscillations, which may indicate the presence of fast-rotating neutron stars in very old X-ray binary systems. The discovery of these oscillations, which was made public in July 1985, has opened up a whole new road of investigation into the bizarre world of neutron stars, a world in which, because of its extreme gravitational conditions, it will be possible to test some of the fundamental laws of physics to their limits.
2.5. ASSERTIONS BY US COMPANIES AGAINST ARIANE COMMERCIAL LAUNCH POUCIES6
On 17 July 1985, the President of the United States signed a decision relieving the European Space Agency and its Member States from any further investigation or action under Section 301(a) of the US Trade Act of 1984 as amended (19 USC 24 11(a)), a statute aimed at protecting US foreign trade interests. c5’ESA News Release No. 21 of 19 July 1985. @)ESA News Release No. 22 of 24 July 1985.
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