18 October 2012, 10:03

INTEGRAL marks 10 years in orbit

INTEGRAL marks 10 years in orbit

Ten years ago the INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL for short) began its orbital vigil. Having now travelled some 430 million kilometres, it is still peering into the most obscure regions of our Galaxy and beyond, providing scientists with abundant data about the most violent phenomena in our universe. Its mission is now extended until the end of 2016 though it still has enough fuel to keep it working until 2023.

INTEGRAL studies the sky through hard X-rays, which allow astronomers to peep through clouds of dust and gas that normally hide many objects from observers by absorbing less energetic radiation. INTEGRAL's objectives are the most extreme bodies and processes in the Universe; supernovae explosions and their remnants, compact objects like white dwarfs, neutron stars, and black holes, which combine very large mass with a relatively small size, the interaction of interstellar matter with cosmic rays and so much more. Since its launch, INTEGRAL has orbited the Earth 1222 times and is currently gazing into the very centre of our own Galaxy.

A joint project between the European Space Agency (ESA), the US National Aeronautics and Space Administration (NASA), the Federal Space Agency of Russia (Roscosmos) and several other countries, INTEGRAL was carried into space in 2002 by the Russian Proton launcher with DM booster. Russian experts have also contributed much to the orbit and insertion calculations, performed with astonishing accuracy, thus saving enough propellant for the observatory to remain at work until 2023 if needed, way beyond the initially planned 2007.

Russia’s participation in the project also includes one quarter of available observational time, which is competitively distributed among Russian scientific organisations.

The most celebrated findings of INTEGRAL include revealing the cause of the Galactic ridge mystery, which turned out to be born of a white dwarf in binary systems, the discovery of new X-ray sources and the most sensitive ever X-ray maps of the Galactic plane and several extragalactic regions. Then, thanks to INTEGRAL and a clever trick invented by Russian astrophysics, a diffuse background X-ray radiation was measured, which is thought to originate in very distant, and therefore indiscernible, black holes in the centres of certain galaxies.

Even now, a decade after its launch INTEGRAL remains one of the most effective X-ray instruments. Albeit that its spatial resolution is not as high as that of its counterparts, Chandra (NASA) and XMM-Newton (ESA), it is still high enough and, combined with a wide field of view (which neither XMM-Newton nor Chandra can boast) INTEGRAL has the unique opportunity to make wide-angle surveys and see separate X-ray sources.

Although INTEGRAL does not have an immediate successor within ESA's plans, due to the delay of the ATHENA/IXO project, X-ray astronomy will hopefully be strengthened in the coming years with the help of Japan’s upcoming Astro-H and, in particular, the Spectrum-RG (Russia and Germany) observatories, to be launched in 2013 and 2014 respectively.

The Spectrum-RG project’s current status was presented in early October at the Space Research Institute of the Russian Academy of Sciences, lead organisation for Russia’s scientific payload. The mission is especially dedicated to all-sky surveys, aimed at discovering the most massive galaxy clusters and active galactic nuclei in the Universe. Spectrum-RG is to combine its wide field of view and large detector area, enabling it to perform an all-sky survey sensitive enough to distinguish between separate sources. This data will not only allow scientists to study the properties of the objects under observation but will also provide input information to reveal the nature of dark matter and dark energy, which are amongst the most intriguing mysteries of the Universe that surrounds us.

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