The RGS diagnostic files (*R[1,2]*DII.FIT) are created for each CCD, which is producing diagnostic mode data. It consists of a single image table extension. Diagnostic data are identical to the "Q dumps" (the only difference being the naming convention; see Sect. 4.1.1). As it is possible to have separate, distinct Q dump files associated with a SPECTROSCOPY+Q exposure, separate, distinct exposure numbers are allocated to these files. However, the exposure identifier (keyword EXP_ID) in the header of each file will be associated with the SPECTROSCOPY+Q exposure. Since the RGS uses CCD chips of the same fabrication type as MOS, the diagnostics files have the same structure as described in Sect. 4.1.4.