The first data-processing stage is ingestion and reformatting. All the information in the FRF, OF and AF is extracted and reformatted to produce two binary FITS files, the Science File (SF) and the Housekeeping File (HKF), for each instrument. In order that each SF be homogeneous, a new pair of SF and HKF will be created whenever the instrument mode, telemetry bit rate or satellite attitude changes. The reason for reformatting the data as soon as possible, while they are still almost raw, is so that future users of the Astro-D archive will have access to the primary data in a self-defining format and will not have to possess special knowledge of the original FRF format to analyze them. (However, ISAS will not be storing all the FITS format files due to insufficient storage capacity.) Note that for each FRF, one SF will be produced for each of the four detectors (two GIS, two SIS). The stage-1 files will follow the organization and structure of the revised ROSAT binary FITS files planned for release in February 1992. This will ensure that analysis and archive software which handles ROSAT data, notably IRAF/PROS, will be available for Astro-Ddata from the outset.
After the conversion to FITS, the SF and HKF will be concatenated, that is, grouped together according to observation. The SF and HKF are described in more detail below.