SAS home  

  SAS Watchout items  

  List of SAS threads  

Reprocessing of ODFs to generate EPIC concatenated and calibrated event list

This thread illustrates you how to reprocess Observation Data Files (ODF) to obtain calibrated and concatenated event lists, which can be directly used to generated scientific products (images, spectra, light curves) through evselect or xmmselect.

How to reduce EPIC ODFs

  1. set up your SAS environment (following the SAS start-up thread)

  2. run the EPIC reduction meta-tasks. For the MOS:
    For the pn:
That's it! The default values of these meta-tasks are appropriate for most practical cases. You may have a look at the next section to learn how to perform specific reduction sub-tasks using emproc or epproc.

The files produced by epproc are the following:

The files produced by emproc are conceptually the same. The main difference in the naming convention is that the string EPN is replaced by EMOS1 and EMOS2 for each MOS camera, respectively.

How to accomplish specific reduction tasks

emproc and epproc are highly flexible tasks, which allow the user to perform a wide range of customized reduction tasks. Some emproc examples are listed below. The same customized reduction tasks can be performed for the pn as well, just by substituting in these commands emproc with epproc. Please, be aware that if you want to supply coordinates for the analysis of Timing and Burst pn mode, the command is slightly different:
epproc withsrccoords=yes srcra=34.65646 srcdec=-12.876546

Parameters can be combined to accomplish simultaneously two or more of the above tasks during the same run.

The user is referred to the on-line documentation of emproc and epproc for a complete list of the available options.

Should I indeed bother to regenerate my event lists?

Concatenated and calibrated EPIC event lists are already available in the PPS Pipeline Products. These are produced with the most updated software and calibrations available at the moment the observation was performed and - normally a couple of weeks later - the ODF are produced. There is therefore no need for you to regenerate the EPIC event lists yourself, unless substantial changes in the software and/or calibration occurred between the time when Pipeline Products were generated and the moment you are analyzing the data. Of course, there is no general answer or recipe one can apply to decide if/when this is the case. In order to collect all the available and necessary elements to formulate your judgment, follow these steps:
  1. check in the XMM-Newton Science Archive the SAS version and the date when the Calibration Index File was generated to produce the Pipeline Products (a primary introduction to the usage of the science archive is available here)
  2. verify in the SAS release notes the software changes between the version employed to produce the Pipeline Products and the latest SAS version
  3. verify in the CCF release notes the changes in the calibration files between the moment when Pipeline Products were generated and the moment your analysis is being performed If your feel lost or unsure, and prefer to stay on the safe side, you'd probably better regenerate your EPIC calibrated event lists.