Useful to know!

• How do I get some help with the executables?
  All the available help files are stored under $ISDC_ENV/help. To visualize a help file interactively type tool_name -h once your environment is set (i.e. the command which tool_name properly returns the path to it).

• Where are the parameter files and how can I modify them?
  All the available executables for the analysis of INTEGRAL data are under $ISDC_ENV/bin/. The corresponding parameter files are stored under $ISDC_ENV/pfiles/*.par. The first time you launch a script, the system will copy the specific tool.par from $ISDC_ENV/pfiles/ to a local directory ( user_name/pfiles/). The parameter file in the local directory is the one used for the analysis and is the one you can modify. If this parameter file is missing (e.g. you have deleted it), the system will just re-copy it from $ISDC_ENV/pfiles/ as soon as you launch the script again. When installing a new version of OSA, it is safe to update your local instance of pfiles, because some default parameter values may have changed and using the old ones may badly influence the results of your analysis. You can do this with: cp -r $ISDC_ENV/pfiles/ /. Removing them instead is not a good solution as they will be missed when running og_create (see Sect. ). The system knows what to copy from where thanks to the $PFILES environment variable that is also used in (FTOOLS). Each parameter is characterized with a letter that specifies its type, i.e:
  • `q' (query) parameters are always asked to the user
  • `h' (hidden) parameters are not asked to the user and the indicated value is used
  • `l' (learned) parameters are updated with the user's value during the use of the program
  The GUI is a fast and easy way to change the parameters, see section for details.

• What are groups and indexes?
  The ISDC software makes extensive use of groups and indexes. While it is not necessary to grasp all the details of these concepts, a basic understanding is certainly quite useful.

  As implied by their names, "groups" make possible the grouping of data that are logically connected. Groups can be seen as a kind of data container, not completely unlike standard directories. At ISDC, we create separate groups for each pointing, in which we store the many different data types produced by INTEGRAL and its instruments. The user then only has to care about one file, the group, many tens of files being silently included. Several pointings (the ``Science Window Groups'') can be arbitrarily grouped into bigger groups (the ``Observation Group'') to select data very efficiently according to the user's needs.

  Indexes are a special kind of groups, which differ only in the fact that all the the data sets they contain are similar and that the indexes know the properties of the data sets they contain. Indexes are a kind of poor man's database. For example, an imaging program creates several images of different types (flux map, significance map,...) in different energy bands. These images are stored in an index, in which the image type and energy band information is replicated. ISDC software is then able to select very efficiently the needed images. The user can also make use of the indexes; just by looking at the index (for instance using "fv"), the user can identify immediately the content of each image.

• Why do I sometimes have to add a `[1]' after a FITS file name?
  A FITS file can have many extensions and sometimes it is necessary to specify as input to a given parameter not the file name alone (file.fits) but the extension too (file.fits[1], or file.fits[2], etc). The file name with a specified data structure (extension) is called a Data Object Locator (DOL). When you modify the parameter file itself (see above) or use the GUI, the extension will be correctly interpreted in the file.fits[1] case. On the command line though, the normal CFITSIO and FTOOLS rules apply, i.e. you have to specify it as one of the following:
  file.fits [1]
  file.fits+1
  "file.fits[1]".
  Note that the numbering starts with `[0]' but often this extension does not contain real data. If no extension is specified explicitly the first one (`[1]') will thus be used by default.

You will find many more useful information in the ISDC list of Frequently Asked Questions (FAQ) at:
http://www.isdc.unige.ch/integral/support/faq