... Unless you have read your FOS data from very old data tapes, the data you have on your machine will be in FITS format. ... c2* files as these contain the flux-calibrated data, wavelengths and errors for an exposure. ... Flat-fielded sky spectra . ... The science data files, science header line files, and the science trailer files have corresponding data quality files that contain the flags for bad or suspect data. ... The calibration pipeline used reference files and tables to flux calibrate FOS...