acis_clear_status_bits

Context: tools

Synopsis

Clear (set to 0) ACIS status bits before reprocessing with acis_process_events

Syntax

acis_clear_status_bits evtfile

This script clears out several ACIS status bits that are set by the Chandra pipeline and that need to be cleared before using acis_process_events. This is needed to support the (new to CIAO 4.4) bad-pixel/afterglow pipeline. Please see the Reprocessing Data to Create a New Level=2 Event File thread for more information.

Unlike most CIAO scripts and tools, this script does not have a parameter file as there is only one argument, the file name of the event file to change. This change happens "in place", so ensure you either have a backup copy of the event file, or can re-create it, before using this script.

Example

unix% acis_clear_status_bits evt1.fits
unix% dmkeypar evt1.fits CLSTBITS echo+
11111111011000000011111111000001

The status bits are cleared from the file evt1.fits. The CLSTBITS keyword is described in the "What bits are cleared?" section below.

What bits are cleared?

The ACIS status column is a 32-bit value. This scripts clears - sets to 0 - bit numbers 1 to 5, 14 to 20, and 23. The numbering here matches that used in the Status dictionary entry on the CIAO web site.

The scripts adds the CLSTBITS keywords to the file, with a value showing the bit mask that was and-ed against each entry (so 0 means the bit was cleared and 1 means that the initial setting is retained). The example above shows the value used for this keyword.