INFO 06-2000: Farewell to a Legendary Mission
14 March 2000What happens with an astronomical satellite after it is switched off? Answer: it keeps producing science. That is at least the true of the legendary International Ultraviolet Explorer (IUE) satellite, an ESA/NASA/UK project. IUE was the first space observatory ever launched and also the one that lived the longest - nearly two decades! This week ESA will release the new IUE archive (INES), the first astronomical database distributed to national data centres all over the world for faster and easier access. This new archive will no longer belong to ESA but to the entire scientific community.
"This is the best farewell from ESA to an historic mission. Thanks to the new distributed system the IUE archive will become both a mine of discoveries and a powerful educational aid for future astronomers. It is a legacy worthy of the IUE project," says Willem Wamsteker, ESA astronomer and ESA IUE Project Scientist.
The IUE Archive, storing two decades of ultraviolet astronomy, has become a historical reference. It contains more than 110 000 spectra from observations that in most cases cannot be repeated, and is an excellent source for studying variable phenomena. The long time-lapse covered and the stability of the instrument have enabled astronomers to witness events they never thought they would, such as the metamorphosis of a very old star into a beautiful planetary nebula: a hot central star surrounded by glowing gas and dust. The IUE archive was the first astronomical archive accessible online -- back in 1985, when the World Wide Web did not even exist-- and has been a key catalyst for science: it has triggered the publication of 3 600 articles in refereed journals so far, and a whole generation of astrophysicists have used IUE data at some stage.
During IUE's lifetime the archive was managed by ESA, from the Villafranca Satellite Tracking Station near Madrid (Spain). But not any longer. The IUE archive will now belong to the world scientific community. ESA has created INES (IUE Newly Extracted Spectra), a distribution system that allows IUE data to be accessed faster and more easily from non-ESA national hosts throughout the world, managed entirely by local experts. INES maintenance costs are minimal, and the system is designed for ready incorporation of whatever innovations might come in the future.
"The INES system and its data guarantee that future generations of astronomers will be able to use IUE data as much as they want, regardless of whether they know about the technicalities of the mission or whether there is an improvement in archive technology. And the distributed structure is better adapted to changes in user needs than a single archive centre," says Antonio Talavera from the Laboratory for Space Astrophysics and Theoretical Physics (LAEFF), based at Villafranca, "ESA has created INES using a minimalist engineering approach for the world scientific community, and has made it to last. INES is easy to use and easy to upgrade, and LAEFF in Spain is proud to serve as the hub for the whole world."
The INES Principal Centre is at the LAEFF, owned by INTA, the Spanish National Institute for Aerospace Technology. This centre, with a data mirror at the CADC in Victoria (Canada), holds the complete database and provides information not available from national hosts. So far 17 national hosts (listed below) have come online. Together they form with the Principal Centre an efficient and highly reliable distribution system for the community. The whole process of data retrieval is fully automated and totally transparent to the end user. This distributed structure avoids localised connectivity problems and guarantees availability of data.
The release of INES will be celebrated on 21 March with a ceremony at the ESA/VILSPA Satellite Tracking Station in Villafranca near Madrid (see Links for agenda and accreditation form). At various other national hosts the release of the INES system will also be celebrated by local academic and demonstration events on different dates.
The ESA/NASA/UK IUE spacecraft, launched in January 1978, became the first space observatory facility available to the whole astronomical community. It marked the beginning of UV astronomy, a field for which space telescopes are essential because UV light does not reach the Earth's surface. By the time IUE was switched off, in September 1996 - 14 years later than originally planned - IUE had changed the view astronomers had of the universe. Among many other findings, IUE discovered the auroras in Jupiter; detected for the first time the halo in our galaxy - a large amount of very hot matter in the outskirts of the Milky Way (the halo); and measured the size of a black hole in the core of an active galaxy.
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List of national hosts
Summary information on INES national host institutes and URL addresses: