4. Data analysis software

  The BeppoSAX Operations Control Center will not perform any processing of the scientific data which means that observers will receive a time-ordered telemetry stream separated into event and housekeeping data for each interval of contiguous instrument configuration and spacecraft pointing. In addition, auxiliary data such as the geomagnetic cutoff rigidity and the angle of the instrument's pointing axis with respect to the Earth's limb are not present on BeppoSAX data tapes and have to be calculated if they are to be used for data screening. Since the event files cannot be directly read into any of the major data reduction packages currently in use by the astronomical community, a dedicated LECS software package has been developed by SSD which will be made available to observers through the BeppoSAX operations center in Rome.

The LECS software allows the following steps to be performed:

• Conversion of the event and housekeeping telemetry files into a set of FITS format files, following the conventions which are becoming a de facto standard in the astronomical community.
• Generation of auxiliary quantities data.
• Monitoring of relevant housekeeping parameters.
• Determination of the gain of the two calibration sources.
• Selection of the ``good'' events and time intervals and rejection of background events, based on criteria such as VETO and BL ranges, position in the FOV, Earth limb angle, etc.
• Conversion from raw PHA channels to PI channels for each event using the gain of the two calibration sources as input (see Sect. 3.1 (click here)).
• Linearization of event positions using the calibration data (see Sect. 3.6 (click here)) and conversion to sky coordinates.
• Extraction of images, spectra and light curves for subsequent scientific analysis.
• Generation of the detector response matrix for the source being analyzed, using as input the extracted spectrum and relevant calibration data.

Two options are available in the LECS data analysis system to correct the PI data for the effects of penetration. The first is to leave the observed spectra uncorrected i.e. with non-Gaussian tails at energies where the penetration depth is significant (see Fig. 12 (click here)) and to generate the appropriate detector response matrix incorporating this effect. The second option is to correct the PI data based on event BL as described in Sect. 3.3 (click here) and so obtain the best possible spectral resolution from the instrument.

The LECS calibration data are stored in a database which is accessed at run time by the relevant modules. This makes updates of the calibration simpler, as no modification or re-compilation of the software is necessary, and only the relevant calibration files have to be updated in the database.

Acknowledgements

We thank M. Adriaens, S. Andersson, E. Dutruel and T. Paulsen for their support during the development and testing of the LECS. H. Brauninger, W. Burkert, C. Erd, R. Much and A. Poelaert are thanked for their support during calibrations. B. Sacco and G. Conti are thanked for providing information on the calibration of the BeppoSAX mirrors prior to publication and A. Smith is thanked for discussions. E. Kuulkers acknowledges an ESA Research Fellowship. Finally, we thank the ASI Space Segment project manager, R.C. Butler, for his tireless efforts on behalf of BeppoSAX.