XMM-Newton Science Analysis System: User Guide

6.6 Running the OM data processing

The data package received by the investigator contains OM data which normally do not necessitate further processing for the purpose of calibration. However, a user may want to apply the most recent calibration, or to change some default parameters to e.g. improve the source detection on his/her data. It may not be necessary to run the complete chains, but just some tasks. All this can be done interactively.

The SAS_ODF environment variable shall be set to the directory containing the raw data, or directly to the SAS summary file, and access to calibration files shall be set through cifbuild (see § 2.3).

The OM tasks and chains can be run in a different working directory to that where the raw (ODF) data reside, providing that the environment variables are properly set.

Invoking omichain, omfchain or omgchain will automatically start the processing of all referred OM data. The duration of the process will depend on the number of exposures and windows, and at the end, the working directory will contain the processed files described before. Some intermediate files will be preserved as well.

Currently only omichain can accept parameters to limit the processing to a given filter or a given exposure:

     omichain filters=filters    (V, B, U, UVW1, UVM2, UVW2)

     omichain exposures=exposures   (letter S or U + exposure numbers)

  e.g.
          omichain filters=V
          omichain filters="U B V"
          omichain exposures=S006
          omichain exposures="S006 S007 U008"

Some of the default parameters used by individual tasks can also be tuned. To see all possible parameters, run:

     omichain -h

In the following examples, it is shown how to run all the tasks that form a chain. The fundamental parameters needed by each task are outlined. For a detailed description of all possible parameters, the user is referred to the section of the SAS online documentation with a description of all the SAS tasks at:

http://xmm-tools.cosmos.esa.int/external/sas/current/doc/

For a better understanding of the processing done by any of the chains, it is recommended to re-direct their screen output to a log file. This will allow the user to examine the process and to see if there is any error or anomaly.

If a user wants to fully understand the process, then running a chain task by task may be useful. In this case it is recommended to have the raw data to be processed and the auxiliary files in the working directory.