ROSAT Guest Observer Facility

Are there specific signs of good data (or, the converse)?


  1. a master veto rate less than 170 indicates good data (master veto rate is defined in the "count-rates" question); above 170 counts/sec, there are unpredictable background "enhancements". These enhancements largely affect the lowest 15 channels. The enhancements are not yet understood.

  2. Look closely at the image of the full photon file (PSPC data). You should see ONE spoke on either side of the main support ring. This spoke is relatively sharp as it was parallel to the wobble direction. The other spokes should be faintly visible at intervals of 45 degrees. A faint spoke appearing closer than 45 degrees from another spoke is the sign of a different aspect solution or a different roll angle. Likely, it will be a relatively brief exposure done well before or well after the bulk of the observations. For an on-axis source, it will not be a problem. For an off-axis source, you will need to be careful not to include those photons in as "background" (especially if you define your background as an annulus about the source).

  3. the presence of scattered solar x-rays appears as an upwardly-going "exponential" curve in a count rate versus time plot, and usually appears at the start or the end of an observation sequence as Earth block starts/ends.

  4. an upturn in the background spectrum in the lowest channels indicates a contribution from afterpulses (pulses generated following a strong pulse). These times and events must be filtered out of the data.

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This file was last modified on Monday, 13-Sep-1999 15:47:41 EDT

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