The ISO Data Archive (IDA) It has been mentioned that ISO
performed around 30 000 science observations. If account is
taken of obser-vations made in the parallel and serendipity
modes of the instruments (observational modes in which an
instrument could observe while another instrument was prime)
almost 150 000 data sets were recorded with ISO. Since ISO was
operated as an observatory with four complex instruments, the
resulting data is very heterogeneous. The data underwent
sophisticated processing, including validation and accuracy
analysis. In total, there exist around 400 Gb of data. To
provide this data to the user community a sophisticated archive
has been developed by ISO Data Centre with continuous and
fruitful cooperation between users and developers to provide a
unique state-of-the art astronomical data archive. In addition
to the observational data products, the archive also contains
satellite housekeeping data, software tools, documentation, and
externally derived products. The IDA is based on an o