The BIAS calibration reference frames in the following table replace the ones retrievable from the HST Archive and are for use with science data from which the highly erratic Side-2 herring-bone pattern noise was removed and in which the error due to pattern noise residuals in the bias reference images contributes significantly to the total error budget (e.g., low S/N exposures of extended objects, faint but crowded star fields, faint emission or absorption lines on faint continua, etc..). For each STScI/OPUS calibration frame, a replacement calibration frame was generated using IRAF script rj_refbias within a custom external layered package (rjstis; Jansen 2005,2012) from raw STIS/CCD bias frames from which the pattern noise was first removed using autofilet.

The resulting new BIAS calibration reference files were renamed to match the original names, so calstis may be run without having to modify the BIASFILE keyword value in the primary header of each science dataset. The FILENAME keyword value in the primary header of the new BIAS calibration images, however, reflects the new root name tabulated in the 4th column (newroot) below. Each FITS header contains an extensive HISTORY section that lists the individual bias frames included and that explains the procedure followed.

In most browsers, one can right-click on the name of a dataset and select "Save As" to download the corresponding noise pattern residuals-free Multi-Extension FITS (MEF) file. Note that each MEF file is ~10 Mb in size and that one may need to specify the download to be in binary mode.