Querying the CALDB

Many of the CIAO tools—such as acis_process_events, mkwarf, and tg_resolve_events—access the CALDB in order to obtain calibration files to apply to the data. Instead of requiring the user to specify the exact filename and path, the tools use header information and other parameter values to find the necessary files from the CALDB.

It is also possible to query the CALDB directly. There are three pieces of information that are needed:

1. the codename

   Each file type stored in the CALDB has an associated codename, which is given in the Codenames table. For example, if you wanted to find the gain file to use for an ACIS observation, the codename would be DET_GAIN.

2. keywords

   In order for the CALDB to find the file that matches your data set it needs to be told a number of facts about the observation, such as what detector was in the focal plane and the time of the observation. The keywords and allowed values are are listed in the Keyword specifications table.

3. boundary conditions

   In order to find certain files—i.e. for specific codenames—it is necessary to supply extra information in the form of boundary conditions. For some tools these conditions are written in a FORTRAN-like style: e.g. cti_corr.eq.yes, which means that the file must be valid for CTI-corrected data.

The sections below descibe the methods you can use to access the CALDB:

• using the calquiz tool;
• from Python