SASS Processing Versions (Rev's):

Currently, the archive holdings contain datasets processsed using three different versions (Revs) of the SASS processing software: Rev 0, Rev 1, and Rev 2.

• Rev 0: The initial release of SASS, used for data processed before Jan 1993.
  • Follow-on observations were combined with previously obtained data and sent to the user (and the archives) under the original data set entry ID, as the additional data became available.
  • Exact copies of only the basic data sets sent to the PI were archived; no results files (e.g. source lists, spectra, light curves) are available.
  • German/UK data and US data were archived in different formats, in the German ROD FITS and US ROD FITS formats, respectively.

• Rev 1: Used for data processed between January 1993 and April 1994.
  • Improved handling of individual sources, from detection through analysis.
  • Incorporated corrections necessary for proper event timing and improved spectral analysis:
    • Bugs in the timing of individual PSPC and HRI events were corrected.
    • Data were screened by aspect solution, with rejection of intervals of too large aspect deviation from nominal.
    • Data were screened according to the correct HV flag.
    • New PSPC spectral response matrix was made available.
    • A new PSPC instrument map was derived from survey data of the secondary PSPC.
    • Wide Field Camera aspect solutions were used for some time intervals.
  • No longer combined observations if their separation exceeded several months, due to possible relative positional differences (up to 20 arcsec) introduced by boresighting and other irreproducible errors.
  • A single observation sequence may therefore consist of several datasets, each with different entry ID, e.g. RP123456N00 and RP123456A01. To get the entire observation sequence, an archive user would need to retrieve both datasets.

• Rev 1: Used for data processed after April 1994.
  • Included all of the improvements of the Rev 1 processing.
  • Unified the German and US data into a single set of FITS formats.
  • Distinguished between accurate pointings (targeting was as scheduled) and mis-pointings (targeting was not as scheduled.)
  • Eventually All ROSAT data will have been reprocessed using the Rev 2 software.

To learn more about dataset naming conventions by Rev, see Naming Conventions.

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Last Update 04 March 1997 (GAR)