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Next: Visual Inspection Up: The ROSAT  Results Archive Previous: The Concept of Threshold

Operational Procedures

GSFC and SAO are responsible for screening and flagging all data obtained by US PIs; MPE and Potsdam share the work on the German observations, while Leicester flags the data from UK PIs. There are two parts to the quality checking, an automated one based on quantitative checks of the SASS output, and a second one that requires human evaluation. Whenever one flag depends on another one, this is set automatically (for example if the source position is suspect, the intensity suspect flag is set to TRUE as well). In addition, certain new image products are created, and these are preserved and also made available to the community.

Screening and archiving of the RRA data occurs in the following steps:

  1. ROSAT  pointed data are delivered via an automated pipeline from the ROSAT  Data Centers to the ROSAT  screening centers (in the US at the Goddard Space Flight Center & the Smithsonian Astrophysical Observatory, in Germany at the Max-Planck Institute for Extraterrestrial Physics & the Astronomical Institute of Potsdam, and at Leicester University in the UK).
  2. After delivery, the data are ``pre-screened'' by automated scripts which look for obvious problems (sources near edges or other detector structures, sources in regions of high background, or sources below a S/N threshold). Each field and source gets assigned a set of quality flags by these scripts:

    For each observation, the source characteristics derived by the processing system detection routine and the set of flags are written to an output file.

  3. The pre-screened data are then visually inspected by personnel at the screening centers as a final check on source validity. Visual inspection consists of comparing an overlay of flagged X-ray sources to the X-ray images.
  4. Operators can accept the quality flag settings provided by the automated screening software, override these flags, or set additional flags. Operators may also mark sources missed by the detection software.
  5. Consistency checks are done periodically in order to determine the amount of variation amongst the many operators.
  6. After screening, the data plus quality flags are saved to a file. This file is released to the public, along with additional products (images, spectra, lightcurves, etc.).

next up previous
Next: Visual Inspection Up: The ROSAT  Results Archive Previous: The Concept of Threshold
Wed Jun 3 11:20:57 EDT 1998