Observing with Integral
3 April 2000More than 80 astrophysicists from all over the world travelled to the small town of Les Diablerets in the Swiss Alps to learn how to use ESA's Integral satellite, once it is in orbit, to gather powerful gamma-radiation coming from distant objects in the Universe. A gamma-ray telescope is very different from a normal optical telescope. Thus special data analysis is needed to transform the signals measured by the scientific instruments on board Integral to fundamental physical units and images that describe the properties of the radiation entering the telescope
"After years of developing the hardware for the spacecraft it is very nice to see that the science community is now getting prepared to use the observatory", said Integral Project Scientist Christoph Winkler. The so-called Integral Spring School from 29 March to 1 April 2000 was the first opportunity for scientists to learn how to submit a proposal for observing time and to get practical training of data analysis. "There were more participants than we expected", said Thierry Courvoisier, head of the Integral Science Data Centre (ISDC) located near Geneva and organiser of the Spring School. The remote Swiss resort of Les Diablerets is usually better known for skiing than for scientific events.
Scientists who want to observe with Integral will have to submit a proposal to ESA's Integral Science Operations Centre (ISOC) located at Noordwijk, the Netherlands. The experts at ISOC will check each proposal on its feasibility and will then pass it to an independent committee for approval or rejection. With the accepted proposals ISOC will prepare the observing schedule for Integral. The scheduling is a trade off between different drivers. The experts have to optimise the observing efficiency and the scientific return while always keeping in mind the requirements of the observers and the constraints of the spacecraft and the ground segment.
At several workstations set up at Les Diablerets the scientists could practice how to submit a proposal correctly going through a Proposal Generation Tool specially designed by ISOC. But the astrophysicists also got an idea how the satellite's data will be analysed and what kind of results they will finally receive from Integral. The data analysis is the task of the Integral Science Data Centre (ISDC) which forms the link between the scientific output of the instruments and the scientific community. The ISDC translates the data supplied by the spacecraft into fundamental physical units. It archives these processed data and distributes them to the astronomical community worldwide. The ISDC, a consortium of a dozen science institutes, is attached to the Geneva observatory and is located in Versoix, Switzerland.
"There are many young scientists who are particularly interested in observing with Integral," said Thierry Courvoisier. After NASA's decision to switch off and re-enter the Compton Gamma-Ray Observatory back into Earth's atmosphere there will be no other large satellite providing the scientific community with the eagerly awaited new data of gamma-ray sources for some while, until the next missions will be launched. Besides ESA's Integral, within the next two to three years Italy plans to launch its Agile-satellite while NASA will launch Swift and later Glast. "The big advantage of Integral is its energy range which covers the processes of nuclear astrophysics which can be investigated using gamma-ray line spectroscopy," said Christoph Winkler.
With Integral the scientists want to find out how the chemical elements were formed by studying the sites of nucleosynthesis in our Milky Way. Radioactive isotopes being formed during supernova explosions emit characteristic gamma-ray lines that allow a clear identification. Looking for these lines with Integral's spectrometer the scientists will try to understand the physical processes which shaped the pattern of abundances of elements in different parts of the Universe. But observing with Integral will also include studying neutron stars, black holes, active galactic nuclei and the most violent gamma ray bursts.