CIAO "Watch Out" Page

This page lists noteworthy items and issues about the CIAO 4.1 release. For the full list of known issues please review the:

• CIAO bug list
• CIAO Frequently Asked Questions page

Installing & Starting CIAO

Solaris: Untarring the CIAO Software

Solaris users must use GNU tar to unpack the tarfiles. If native Solaris tar is used, some of the smoketest filenames will be truncated.

IPython Packaged with CIAO OTS

CIAO 4.1 includes IPython in the CIAO OTS directory which is used by Sherpa and ChIPS to provide command-line user interfaces. These programs create an IPython profile in the directory $HOME/.ipython-ciao.

If IPython users want any personal customizations to be available when running CIAO, they will have to copy them from $HOME/.ipython to $HOME/.ipython-ciao.

CALDB 4.1 Required

CALDB 4.1 is required in order for CIAO 4.1 to work correctly.

A number of CIAO tools have been updated to be work with CALDB 4.1; read the How CIAO 4.1 and CALDB 4.1 Affect Your Analysis section of the CIAO 4.1 release notes.

Conflicts with Other Software Packages

There are some known conflicts between CIAO and other software or system libraries and tools. Issues not covered in this "Watch Out" page are listed on the "Other Software Packages" bug page.

Data Caveats

Source Detection and Cosmic-Ray Afterglows

CIAO users who are trying to detect sources of about 10 counts or less should be aware of potential confusion with cosmic-ray afterglows that have not been removed from the data.

The Cosmic-Ray Afterglows why topic explains the limitations of the current tools and describes analysis tips to help eliminate more of the afterglows.

Incorrect Exposure Time from Merged Event Files

When multiple event files that have different ranges of exposure numbers (expno column) are merged, the output file will have more than one GTI block for each chip. This causes incorrect exposure values later in the analysis, as the CIAO tools cannot use multiple GTI blocks for a single chip.

Further details and a workaround to this problem are available on the dmmerge bug page.

Spectral analyses of ACIS data with a limited pulse-height range

When performing analyses of ACIS spectral data, it is important to restrict fits to the spectral band over which the data were collected (or to a narrower band). Read the Spectral analyses of ACIS data with a limited pulse-height range caveat for details.

A complete list of caveats for Chandra data is available on the Data Caveats webpage.

Analysis

Specifying Aspect Solution Files

The aspect solution files (pcad..._asol1.fits) are used as inputs to several of the CIAO tools - e.g. acis_process_events, asphist, and tg_resolve_events.

If there is a single aspect solution file, it can be provided directly to the tool:

unix% pset asphist infile=pcadf245733620N002_asol1.fits

In many cases, there will be more than one aspect solution file for an observation. Then all the files must be provided in chronological order. (The time is in the filename, so "ls" lists them in chronological order.) This may be done as a comma-separated list:

unix% pset asphist infile="pcadf063874624N002_asol1.fits,pcadf063875522N002_asol1.fits,pcadf063902942N002_asol1.fits"

The list of aspect solution files may also be given as a stack. Any number of files can be specified in the stack, one:

unix% cat pcad_asol1.lis
pcadf245733620N002_asol1.fits

unix% pset asphist infile=@pcad_asol1.lis

or more than one:

unix% cat pcad_asol1.lis
pcadf063874624N002_asol1.fits
pcadf063875522N002_asol1.fits
pcadf063902942N002_asol1.fits

unix% pset asphist infile=@pcad_asol1.lis

Note that an at symbol ("@") is used before the filename to indicate that it is a stack file.

Using Chips 4.0 Save Files and Scripts in CIAO 4.1

ChIPS state files from CIAO 4.0 - i.e. the files created by "save_state (S-Lang or Python help)" and loaded by "load_state (S-Lang or Python help)" can not be loaded into CIAO 4.1. Please contact the CXC Helpdesk if this is a serious problem for you.

Most ChIPS scripts written for CIAO 4.0 will continue to run in CIAO 4.1. However some code may need updating, as described in the ChIPS upgrade guide. Contact the CXC Helpdesk if you need help in updating CIAO 4.0 ChIPS scripts to CIAO 4.1.