As of November 2003, the ISO Data Archive is still being intensively used by the astronomical community with typically more than 2000 queries executed every month. In its first five years of use, the equivalent of more than 8 times the total number of scientific observations in the archive has been downloaded. In total, there are nearly 1500 registered users, still increasing at an average rate of about one new user every two working days. About 50 to 70 users actually download data every month.
Looking further into the future, first steps have already been taken to prepare the ISO Data Archive for its future integration into the `International Virtual Observatory' concept.
The Virtual Observatory is an international astronomical community-based initiative. It aims to allow global electronic access to the available astronomical data archives of space and ground-based observatories and sky survey databases. It also aims to enable data analysis techniques through a coordinating entity that will provide common standards, and state-of-the-art analysis tools.
With this spirit in mind, the ISO Data Archive currently provides links from individual observations to publications in the NASA ADS2.5 database; the list of ISO observations has been installed in VizieR2.6 (the most complete database of published astronomical catalogues) and links to the ISO Postcard Server (see Chapter 7) are provided from VizieR; and the feasibility to implement direct access to images from Aladin2.7 (an interactive software sky atlas allowing the user to visualize digitized images of any part of the sky and superimpose entries from astronomical catalogues or personal data files) is being assessed. More advanced, value-added functionalities are in preparation, in particular the cross-identification of the list of ISO observations with the astronomical database SIMBAD2.8, which will permit direct links between objects in SIMBAD and the ISO Data Archive, search by object types in the archive, etc.
At the end of the Active Archive Phase, maintenance of the historical archive is expected to be carried out in conjunction with the Herschel Science Centre, under the general auspices of the Research and Scientific Support Department. No additional funding, dedicated to the historical archive, is sought after 31 December 2006.