The European Space Agency has today launched a new observatory set to
revolutionise the branch of astrophysics that seeks to unravel the secrets
of the highest-energy – and therefore the most violent ñ phenomena in the
Universe. This comes 20 years after the end of ESA’s COS-B mission, which
produced a complete map of the sky in the high-energy gamma-ray waveband.

In the framework of ESA’s cooperation with Russia, a Russian Proton
launcher was chosen to place the Integral (INTErnational Gamma-Ray
Astrophysics Laboratory) observatory in orbit. The launcher lifted off
from Baikonur in Kazakhstan today at 10:41 local time (06:41 CEST). After
re-ignition of its upper stage, it placed Integral in its 72-hour
elliptical orbit, ranging from only 10000 km up to 153000 km from the
Earth, i.e. nearly half the distance to the Moon. Controlled by ESAís ESOC
mission operations centre in Darmstadt in Germany, the satellite will now
undergo a two-months test period intended first to verify that the
instruments onboard are working correctly and then that the data they
collect is of good quality.

Integral was developed by Italy’s Alenia Spazio supported by over 30 firms
in Europe. The satellite (mass 4 000 kg, height 5 metres) has two main
instruments: the SPI spectrometer and IBIS imager

Developed by a Franco-German-led team, the spectrometer will conduct a
spectral analysis of isolated sources and of regions of gamma-ray activity
with unprecedented energy resolution (40 times better than previous
satellites), using germanium detectors cooled to 85 K. Since mirrors and
lenses are of no use in detecting gamma rays, the SPI uses the ìcoded-mask
imagingî technique to form its images from very faint radiation. These
images are then decoded by computer.

The imager, designed by an Italian-led team, is the perfect partner for
SPI. It has a weaker energy resolution, but an angular resolution 12 times
sharper thanks to a coded mask optimised for the purpose and two
new-generation detector layers.

To supplement the observations by SPI and IBIS, Integral also carries a
Danish X-ray imager (JEM-X), with twin detectors each fitted with coded
masks, and a Spanish CCD imager (OMC) operating in the visible spectrum
waveband.

By combining the data collected by these four instruments, it will be
possible, for the first time, to make simultaneous observations of
high-energy phenomena at seven orders of magnitude, from visible light to
gamma rays. All the raw data collected by Integral will be sent directly
to the ground via the ESA station at Redu in Belgium, or the station
operated by NASA ñ another partner in the programme ñ at Goldstone in the
USA. The raw data will be centralised at ESOC in order to be processed and
redistributed to the scientific community via the Integral Scientific Data
Centre (ISDC) at Versoix in Switzerland.

Operating in an orbit that enables it to spend most of its time outside
the Van Allen radiation belts, which can hamper observation of cosmic
gamma rays, Integral will primarily study the densest sky objects, such as
neutron stars and black holes, which are all sources of very high energy
radiation. While IBIS will supply very detailed images of these sources,
SPI will conduct the first in-depth analysis of this gamma radiation.
Integralís observations should enable astrophysicists to confirm the
presence of giant black holes at the centre of galaxies, starting with the
Milky Way.

Other areas of interest for the European gamma-ray observatory will
include events of rare violence such as nova and supernova explosions.
These will be explored with precision thanks to the gamma radiation given
off by the radioactive isotopes emitted. Integral will also be a unique
means for observing gamma bursts, these still largely unexplained
explosions at the outer reaches of the Universe, which for the first time
can be studied in parallel along a wide range of the electromagnetic
spectrum.

Integral is the second medium-size mission carried out under the Horizon
2000 programme, following the Huygens probe, whose destination is Saturn
and its moon Titan; the third will be the Planck observatory, which will
study the background noise of the Universe, as from 2007. The Integral
mission should last at least two years.

For further information, please contact:

ESA Media Relations Service
Tel: +33(0)1.53.69.7155
Fax: +33(0)1.53.69.7690