Integral - tracking extreme radiation across the Universe

The world's most advanced gamma-ray space telescope Integral [International Gamma Ray Astrophysics Laboratory] was successfully launched today [17 October 2002] from the Baikonur Cosmodrome, Kazakhstan. Integral will provide first-hand observations of cosmic objects that release some of the most energetic radiation of the Universe.

British scientists from Southampton and Birmingham universities together with colleagues from Mullard Space Science Laboratory, University College London, have played leading roles in providing key instruments for this European Space Agency [ESA] mission., ,Gamma-rays are released by the most violent events in the Universe. Unlike the serene beauty of the stars that we can see with our own eyes, the gamma-ray Universe is a place of dramatic explosions, cosmic collisions, and matter being sucked into black holes. Until now astronomers have only had glimpses of this cosmic maelstrom. However, Integral has four instruments [2 gamma-ray, 1x-ray monitor and 1 optical camera] designed to simultaneously capture gamma rays, X-rays, and visible light from these powerful celestial events, allowing astronomers on Earth to bring them into sharp focus and fully analyse them., ,"Gamma-rays are the most energetic form of radiation in nature and their production is intimately coupled to the physical processes that power the engines of these infernal cosmic machines", commented Prof. Tony Dean of Southampton University. Prof. Dean, together with his colleague Dr. J. Matteson, the original joint proposers of the INTEGRAL mission to ESA way back in 1989 added," the extreme penetrating power of these high-energy photons enables their vital information to escape their source region and reach us distant observers." , ,Dr. Ian Stevens of Birmingham University explains," Because gamma-rays are so penetrating then, unlike light, they cannot be focused with a conventional camera lens. Instead of a lens we use a disc of heavy metal peppered with a pattern of holes such that half of any incoming radiation is let through and half absorbed by the metal disc, producing what we call a 'shadowgram' - which is not a perfect picture. To rectify this and create the kind of images one would normally expect from a camera we have developed special software to enable all Integrals instruments to obtain sharp images, particularly the gamma-ray spectrometer"., ,Southampton University has been directly involved in the second onboard gamma-ray camera, IBIS, the sharpest resolution gamma-ray camera ever built. Additionally, the Southampton team play a key role in the Integral Science Data Centre [ISDC] located near Geneva. Dr. Tony Bird commented," After Integral has collected observations the raw science data is forwarded to the Science Data Centre. It is then converted into usable data files, archived, and distributed very quickly to a world-wide network of space science institutes and observatories. This is essential, especially when sudden and short-lasting phenomena such as gamma-ray bursts occur. In this case all ground-based observatories need to receive the information within one minute in order to be able to immediately point their telescopes at the area of sky where the gamma-ray burst has been detected."
For further information contact:, ,Peter Barratt,PPARC Head of Communications,Tel: [phone],Mobile: [phone],Email: [e-mail], ,Prof. Tony Dean,University of Southampton,Tel: [phone],Email: [e-mail], ,Dr. Antony Bird,University of Southampton,Tel: [phone] ,Email: [e-mail],Or [e-mail], ,Meline Burke,Press Officer,University of Southampton,Tel: [phone],Email: [e-mail], ,Dr. Ian Stevens,University of Birmingham,Tel: [phone],Email: [e-mail], ,Dr. Paul Connell,University of Birmingham,Tel: [phone],Email: [e-mail], ,Dr. Dave Walton,Mullard Space Science Laboratory,University College London,Tel: [phone],Email: [e-mail], ,Images (available on request from [e-mail]), ,1) Russian Proton launcher. Credit: ESA, ,2) INTEGRAL 'structural thermal' model testing at ESTEC. The structure thermal model(STM) of ESA's INTEGRAL gamma-ray observatory was tested in the Large Space Simulator (LSS) at ESTEC in June 1998. Here, it is shown shortly before it was lowered into the chamber. Following the thermal-vacuum testing in the LSS, the STM underwent mass property measurements in the Multi-shaker area, and was then moved into the Large European Acoustic Facility (LEAF). Integral is planned for launch in 2002 to perform fine imaging and spectroscopy of 15 keV to 10 MeV celestial gamma-ray sources. Credit: ESA, ,3) INTEGRAL spectrometer SPI. Spectrometer on INTEGRAL (SPI) overall view. Credit: ESA, ,4) An artist's impression of the INTEGRAL spacecraft. Credit: ESA, ,5) An artist's impression of the INTEGRAL spacecraft. The INTEGRAL mission, due to be launched in October 2002, will gather some of the most energetic radiation that comes from space. With its gamma-ray spectrometer (SPI) and gamma-ray imager (IBIS), it will be the most sensitive gamma-ray observatory ever to be launched. The payload also includes two X-ray monitors (JEM-X) and an optical camera (OMC) to help identify gamma-ray sources. INTEGRAL is an ESA mission in co-operation with Russia. ,Credit: ESA, ,6) Artist impression of black hole candidate accreting material from its larger companion. Credit: ESA, ,7) Black hole candidate - Artist impression of black hole candidate accreting material from its larger companion. Credit: ESA,
Background notes, ,The turbulent Universe,Gamma rays carry large quantities of energy away from the violent events where they are created, such as supernova explosions, black holes, and the mysterious gamma-ray bursts. Integral will find a lot more out about these powerful gamma-ray sources., ,Very massive stars end their lives in big explosions called supernovae. These outbursts liberate more energy than the combined light of millions upon millions of stars, much of it in the form of gamma rays. New chemical elements are created as results of such explosions. In fact all atoms heavier than iron are created due to such explosions. For this reason, we call supernovae the chemical factories" of the Universe. However, we do not know completely how new atoms are created when a star explodes.,Integral will look into it as one of its first scientific objectives., ,After the explosion, each supernova leaves behind a dead 'heart'. This heart is incredibly dense and can be either a neutron star or a black hole. Both can generate gamma rays because they possess incredibly strong gravitational fields that can capture passing dust, gas and, possibly, larger celestial objects. When matter falls through a gravitational field, it heats up and releases energy. In the case of neutron stars and black holes, the energy released is very intense and is given off in the form of x-rays and gamma rays., ,As well as black holes from supernovae, called stellar black holes, the Universe contains a variety of far more massive black holes that are found at the core of some galaxies, the galactic black holes. Galactic black holes also give off gamma rays, and with such awesome power that you can detect them almost halfway across the known Universe., ,As well as making the most accurate studies of these objects to date, Integral will also investigate the mysterious blasts of gamma rays that explode across the Universe about once a day, known as gamma-ray bursts. They can last just a few seconds and can come from any direction in space. The,origin of gamma-ray bursts has remained unexplained for years, from their first observation in the late 1960s. Today, many scientists think that gamma ray bursts could be linked to the death throes of the very first stars. ,Alternatively, they could be generated by colliding neutron stars, or could be caused by the explosion of supermassive stars at the end of their lives, the hypernovae. Integral's instruments will study gamma-ray bursts with the highest accuracy ever and may discover something about their origins.
Integral's instruments,Integral has four instruments to give the spacecraft maximum versatility in its task of studying the gamma-ray Universe. Designed to complement each other, their combined observations will allow scientists to get a very complete and accurate picture of each celestial target at different wavelengths., ,The first two are dedicated gamma-ray instruments. Imager on Board the Integral Satellite (IBIS) is the sharpest-resolution gamma-ray camera ever built. Spectrometer on Integral (SPI) will measure the energy of gamma rays with exceptional accuracy. In particular, it will be more sensitive to fainter radiation than any previous gamma-ray spectrometer. The other two instruments are designed to provide complementary scientific data about Integral's targets. The Joint European X-Ray Monitor (JEM-X) will make observations simultaneously with the main gamma-ray instruments and will provide images at X-ray wavelengths. The Optical Monitoring Camera (OMC) will do the same but at visible-light wavelengths. The total weight of the four instruments is about 2 tonnes, roughly half the launch weight of Integral., ,Integral's orbit and operations ,After launch, Integral will follow an elliptical orbit that is inclined by 51.6° to the Earth's equator. In this orbit, it will cycle between 9000 kilometres and 153 000 kilometres above Earth, completing one revolution of the Earth every 72 hours. This eccentric orbit is necessary because there are 'radiation belts' that surround the Earth and these would interfere with Integral's ability to see gamma rays. It is important for Integral to be outside these belts. Its elliptical orbit is designed to keep it outside the radiation belts for 90% of its trajectory around Earth., ,Once Integral is in orbit, it must communicate with Earth to download its scientific data and to receive commands. Communicating with and controlling Integral is a task spread over a number of different sites. ,Firstly, astronomers submit proposals for observations to the Integral Science Operations Centre (ISOC) at Noordwijk, The Netherlands, where astronomy experts from across the world evaluate the proposals and draw up a list of targets and detailed observation schedules for Integral. The schedules are sent to the Mission Operations Centre (MOC) at the European Space Operations Centre (ESOC) in Darmstadt, Germany. There everything is transformed into commands that Integral will understand. Signals to and from Integral go through two tracking stations, one at Redu in Belgium, the second at Goldstone in California, United States. The MOC also ensures the correct performance of the spacecraft., ,After Integral has collected observations, the raw science data is forwarded to the Integral Science Data Centre (ISDC) in Versoix near Geneva, Switzerland. There it is converted into usable data files,archived, and distributed to the astronomical community. A worldwide network of space science institutes and observatories will receive the data very quickly. This is essential especially when sudden and short-lasting phenomena such as gamma-ray bursts occur. In this case, all observatories need to receive the information within one minute to be able to point their telescopes immediately at the area of the sky where the gamma-ray burst has been detected., ,Building Integral,Integral was selected as a mission by ESA in June 1993. The prime contractor for the spacecraft was Alenia Aerospazio, Turin, Italy. Alenia involved 26 subcontracting companies from 12 European countries to build the spacecraft's service module. This provides the essentials for the spacecraft such as power (via solar panels), satellite control, and the communications link to the ground. Alenia was also responsible for integrating the four science instruments on-board the spacecraft, known collectively as the payload module. Four consortia of academic and industrial partners, variously located throughout Europe, built the instruments. , ,Integral has faced many technological challenges. However, the greatest was finding a way to focus gamma rays, which are so powerful they pass through ordinary mirrors. To overcome this, Integral's gamma-ray instruments and its X-ray monitor use a technique called coded-mask imaging. Instead of focusing, the coded mask blocks some gamma rays, creating a recognisable shadow on the detector beneath. Ground computer systems process the data coming from the gamma-ray detector looking for this shadow. Once it finds the shadow pattern, it groups the gamma rays together, forming an image. Gamma rays from different astronomical objects enter the instruments at different angles and so cast different shadows, allowing gamma rays from multiple sources to be separated.
Integral has been developed and built at a cost of 330 million Euros. This price does not include the cost of launch, which Russia is providing free in exchange for observing time on Integral. Neither does the cost include the price of the science instruments, which have been provided by academic and industrial consortia. To reduce costs, the design for the service module was reused from ESA's XMM-Newton satellite., ,Historical perspective on gamma-ray astronomy,Scientists have placed small gamma-ray detectors on satellites since the early 1960s. However, the most extraordinary discovery came in the late 1960s from a series of military satellites designed to monitor the ban on nuclear bombs being tested on Earth. These satellites detected the appropriately named gamma-ray bursts, which explode without warning about once a day, from random directions in the sky., ,In 1972, the NASA probe SAS-2 confirmed that the Universe is bathed in a perpetual shower of gamma rays. In 1975, ESA launched the gamma-ray satellite COS-B, that worked until being switched off in 1982. , ,COS-B produced the first map of the gamma-ray sky and identified a number of bright gamma ray sources. It was followed by the Russian-French mission GRANAT, in 1989-1998, and NASA's Compton Gamma-ray Observatory (CGRO), in 1991-2000. The CGRO satellite greatly increased our understanding of gamma-ray astronomy. Soon we can expect Integral to dazzle the world with the next leap in technology. , ,PPARC,The Particle Physics and Astronomy Research Council (PPARC) is the UK's strategic science investment agency. It funds research, education and public understanding in four broad areas of science - particle physics, astronomy, cosmology and space science. , ,PPARC is government funded and provides research grants and studentships to scientists in British universities, gives researchers acess to world-class facilities and funds the UK membership of international bodies such as the European Organisation for Nuclear Research, CERN, the European Southern Observatory and the European Space Agency. It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, the UK Astronomy Technology Centre at the Royal Observatory, Edinburgh and the MERLIN/VLBI National Facility.
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