Why am I getting an ARDLIB error about a bad pixel file from a different ObsID?

***ARDLIB error: Unable to find data file acisf01842_000N002_bpix1.fits[BADPIX7]

If a tool complains about a bad pixel file from a different observation than the one with which you are working, it usually indicates that you have forgotten to "punlearn" the ardlib.par file since the prior analysis session. Since CIAO does not assume a particular directory structure, it uses the information set by the user in ardlib.par to locate the correct bad pixel file for the current analysis session.

If you "plist ardlib", you should see the filename from the error message:

unix% plist ardlib
...
#---------------------------------------------------------------------------
# AXAF ACIS Bad Pixel Files
# Use "NONE" to ignore bad pixels.
#---------------------------------------------------------------------------
AXAF_ACIS0_BADPIX_FILE = acisf01842_000N002_bpix1.fits[BADPIX0] Enter ACIS-0 Bad Pixel File
AXAF_ACIS1_BADPIX_FILE = acisf01842_000N002_bpix1.fits[BADPIX1] Enter ACIS-1 Bad Pixel File
AXAF_ACIS2_BADPIX_FILE = acisf01842_000N002_bpix1.fits[BADPIX2] Enter ACIS-2 Bad Pixel File
AXAF_ACIS3_BADPIX_FILE = acisf01842_000N002_bpix1.fits[BADPIX3] Enter ACIS-3 Bad Pixel File
AXAF_ACIS4_BADPIX_FILE = CALDB            Enter ACIS-4 Bad Pixel File
AXAF_ACIS5_BADPIX_FILE = CALDB            Enter ACIS-5 Bad Pixel File
AXAF_ACIS6_BADPIX_FILE = acisf01842_000N002_bpix1.fits[BADPIX6] Enter ACIS-6 Bad Pixel File
AXAF_ACIS7_BADPIX_FILE = acisf01842_000N002_bpix1.fits[BADPIX7] Enter ACIS-7 Bad Pixel File
AXAF_ACIS8_BADPIX_FILE = CALDB            Enter ACIS-8 Bad Pixel File
AXAF_ACIS9_BADPIX_FILE = CALDB            Enter ACIS-9 Bad Pixel File
...

To update ardlib.par, follow the Setting the Observation-specific Bad Pixel Files thread.

If you wish to maintain several ardlib.par files, e.g. for different ObsIDs and/or analysis sessions, refer to the How do I run multiple instances of a CIAO tool without clobbering the parameter file? FAQ.