... Reference Files . ... Reference files used by the ACS calibration pipeline (CALACS and PyDrizzle/MultiDrizzle) are updated on a regular basis. ... If you would like to receive an e-mail every time a new ACS reference file is delivered and the database is updated, you can subscribe to the acs_reffiles_upd mailing list. ... The pixels affected by these reference files are generally identified by data quality flags in the [DQ] extension of calibrated FITS data. ... ACS Distortion Correction Tables . ...