The stability of the IUE instrument, and the care taken to ensure a proper calibration throughout the mission, make the IUE database a very valuable archival resource for specific investigations in the domain of astronomical ultraviolet spectroscopy.
The IUE Uniform Low-Dispersion Archive (ULDA) was the first attempt to put the results of IUE at the disposition of the astronomical community in an orderly manner. Version 3.0 of the ULDA was released in September 1990 and contained 98.7% of all the low-resolution spectra obtained by IUE before January 1, 1989 (44,000 spectra). The ULDA was installed at a number of national hosts and was made available to general users from these hosts.
The lasting value of the IUE archive became even more evident after the final reprocessing of all the low-dispersion spectra into the final IUE Newly Extracted Spectral Archive (INES) was completed. The reprocessing was done using improved extraction techniques and calibrations (NEWSIPS: Nichols et al. 1993). The IUE Final Archive, another collaborative effort by NASA, ESA, and PPARC, was identified during the final phase of the mission as a necessary step in the production of a high-quality and uniform data base. This archive was seen as the final repository of the information collected by IUE, produced at a stage when specialized knowledge of the instrument and of its calibration procedures were still available. The final archive will be maintained accessible to the scientific community as the historical reference of the IUE mission and as a source of information for future studies based on IUE UV spectra. It is a special tribute to the leadership of the IUE project that most of the final archive production was done while the satellite was still in operation.
The final version of the IUE archive contains 104,471 spectra reprocessed with the most up-to-date calibration and includes high-resolution echelle spectra binned to the resolution of the low dispersion observations. The low-resolution version of the IUE archive has been installed at the ESA/INTA INES Primary Center at VILSPA/LAEFF and at 19 national or institutional hosts (as of 18 February 2000).