INFO 30-1998: ESA presents INTEGRAL
11 September 1998
Deciphering the processes of the Universe's alchemy which fabricate the elements of stars and galaxies, as well as theendpoints of stellar life, will be the tasks of ESA's INTEGRAL satellite, the INTErnational Gamma-Ray AstrophysicsLaboratory. Gamma-rays are a million times more energetic than visible light and bring us information from stupendousphysical events that made the universe habitable.A unique opportunity for journalists and cameramen to view INTEGRAL will be provided at ESA/ESTEC, Noordwijk,The Netherlands on Tuesday 22 September.On show will be the full-size structural thermal model which is now being examined in ESA's test centre. Following introductions to the project, the INTEGRAL spacecraft can be seen, filmed and photographed in its special clean room environment.
Gamma-ray astronomy - why ?
Gamma-rays cannot be detected from the ground since the earth's atmosphere shields us from high energetic radiation. Only space technology has made gamma-astronomy possible. To avoid background radiation effects INTEGRAL will spend most of its time in the orbit outside earth's radiation belts above an altitude of 40 000 km.
Gamma-rays are the highest energy form of electromagnetic radiation. Therefore gamma-ray astronomy explores the most energetic phenomena occurring in nature and addresses some of the most fundamental problems in physics. We know for instance that most of the chemical elements in our bodies come from long-dead stars. But how were these elements formed? INTEGRAL will register gamma-ray evidence of element-making.
Gamma-rays also appear when matter squirms in the intense gravity of collapsed stars or black holes. One of the most important scientific objectives of INTEGRAL is to study such compact objects as neutron stars or black holes. Besides stellar black holes there may exist much bigger specimens of these extremely dense objects. Most astronomers believe that in the heart of our Milky Way as in the centre of other galaxies there may lurk giant black holes. INTEGRAL will have to find evidence of these exotic objects.
Even more strange than the energetic radiation coming from the centre of distant galaxies are flashes of extremely powerful radiation that suddenly appear somewhere on the gamma-sky and disappear again after a short time. These gamma-bursts seem to be the biggest observed explosions in the Universe. But nobody knows their source. Integral will help to solve this long-standing mystery.
Two main instruments observe the gamma-rays. An imager will give the sharpest gamma-ray images. It is provided by a consortium led by an Italian scientist. Gamma-rays ignore lenses and mirror, so INTEGRAL makes its images with so-called coded-masks. A coded-mask telescope is basically a pinhole camera, but with a larger aperture, i.e. many pinholes.
A spectrometer will gauge gamma-ray energies extremely precisely. It is developed by a team of scientists under joint French-German leadership and will be a 100 times more sensitive than the previous high spectral resolution space instrument. It is made of a high-purity Germanium detector that has to be cooled down to minus 188 degree Celsius.
These two gamma-ray-instruments are supported by two monitor instruments that play a crucial role in the detection and identification of the gamma-ray sources. An X-ray monitor developed in Denmark will observe X-rays, still powerful but less energetic than gamma-rays. An optical telescope provided by Spain will observe the visible light emitted by the energetic objects. Switzerland will host the Integral Science Data Centre which will preprocess and distribute the scientific data.
The mission is conceived as an observatory led by ESA with Russia contributing the launcher and NASA providing tracking support with its Deep Space Network. Alenia Aerospazio in Turin, Italy is ESA's prime contractor for building INTEGRAL. Launch by a Russian Proton rocket from Baikonur is actually scheduled for 2001.
ESA pioneered gamma-ray astronomy in space with its COS-B satellite (1975). Russia's Granat (1989) and NASA's Compton GRO (1991) followed. But INTEGRAL will be better still. With this mission ESA will further strengthen its lead in gamma-astronomy.
Principal Investigators
Imager: Pietro Ubertini (IAS, Frascati, Italy)Spectrometer: Gilbert Vedrenne (CESR, Toulouse/France) Volker Schoenfelder (MPE, Garching/Germany)
X-Ray monitor: Niels Lund (DSRI, Copenhagen/Denmark)
Optical Monitoring Camera: Alvaro Gimenez (INTA, Madrid/Spain)
Integral Science Data Centre: Thierry Courvoisier (Genova Observatory, Switzerland)
