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Status of EPIC time jump problems

Learn about time jump anomalies in EPIC data, their causes, and consequences. Find out how SAS detects and corrects time jumps, and explore the relative timing accuracy in different modes. Get insights into problematic cases and workarounds for improvement.

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Status of EPIC time jump problems

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  1. Status of EPIC time jump problems Marcus G. F. Kirsch, M.J. Freyberg, E. Kendziorra, U. Lammers

  2. Time jumps • mid-2000 first discovered pn-AUX data anomalies: • frequency of occurrence is variable • unrelated to camera mode, observing time or duration • some data sets are completely free of any problems others are heavily affected. • reason: H/W problem of EPEA • consequences: event times turn out wrong • single shift in FTCOARSE time will cause all subsequent times to be wrongly shifted by the same amount. • pulse profile analyses inconclusive because all photons after the instant of the time jump will be out-of-phase • pulse peak broadening, phase shift or the appearance of spurious pulse components. • SAS should find and correct those time jumps

  3. Situation 5.4.1 • Not all negative or positive jumps in FTCOARSE are found and corrected by SAS pulse peak broadening, phase shift spurious pulse components

  4. Experimenting with the detection algorithm: 2-tests 01537503010153750401 0153750501 deltrack deltrack deltrack 6.0 6.0 6.0

  5. Relative Timing accuracy

  6. Status: SAS 6.0 • fast modes: • problems are reliably found and corrected • only 2 know problem cases • imaging modes: • rare cases of very long time jumps (ks) in the imaging modes (< 0.5 %) • still uncorrected time gaps with no integer multiple of frame time (< 2 %) mainly in revs < 220 • list of problematical cases and work around will be provided in document:XMM-Newton EPIC photon arrival times: This document gives an overview of the readout of the EPIC camera and the applied correction to the photon arrival times.

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