eSASS task: gtcal
erosita/gtcal-1.7
Summary:
An interface to return calibration files from the CALDB.
Description:
This is not a task that can be run, but a library designed to provide convenient access to a HEASARC-style calibration database. The subroutine that should be called is gtcalf(), which is described within getcalf.f. No other subroutine need be called directly from user programs.
Each observation is in general characterised by the following pieces of information:
- TELESCOP: the name of the mission or telescope.
- INSTRUME: the name of the instrument.
- DETNAM: the name of the detector (if appropriate).
- FILTER: the name of the applied filter (if appropriate).
- A boolean expression if appropriate, which might for example select on energy ranges.
- A codename if appropriate.
- Start and end dates of the period of validity (can be open-ended).
The gtcal interface returns files from the calibration database which match these criteria. The matching process proceeds through three stages. Only files which pass a stage are considered for the next stage. The stages may be described as follows.
- This stage passes files which match TELESCOP, INSTRUME, DETNAM, FILTER, boolean expression, and codename. If a version number for this combination is found in the $SASS_CALVERS file, this is used to further select files.
- Time filtering, which uses the REF_TIME column in the appropriate calibration index file. This stage first finds the cal file which has the most recent REF_TIME which is less than or equal to the start date of validity that the calling program provides. Files are then passed by the stage which have REF_TIME values ≥ this start value and ≤ the user-supplied stop time.
- If any of the files which pass the preceding stages have the same REF_TIME value, and providing no version was found in the $SASS_CALVERS file, the third stage discards all but the latest version of the equal-REF_TIME files.
Note that the interface may return more than one file. Calling programs must be designed to cope with this.
Parameters:
None.
Input files:
None.
Output files:
None.