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: http://xmm.vilspa.esa.es/sas/7.0.0/doc/epevents/node6.html
Дата изменения: Thu Jun 29 00:29:36 2006 Дата индексирования: Sat Dec 22 09:35:36 2007 Кодировка: Поисковые слова: m 80 |
Depending on the observation mode a certain fraction of the events recorded are due to out-of-time events (OoTE), i.e. are registered during readout of a CCD and thus will be assigned an incorrect position in RAWY and consequently an incorrect CTI correction. Typical values are 6.3% for full frame mode, and 2.3% for extended full frame mode (with FRAME_TIME_PARAMETER=3).
Out-of-time events have a much lower exposure per pixel per read-oiut frame, namely reduced by the number of pixel shifts during readout and by the abovementioned ratio of readout and cycle time. Therefore the likelihood for pile-up is extremely reduced (by more than 3 orders of magnitude). Extremely bright (and hard) sources can trigger the MIP rejection mechanism (see epframes) due to pile-up: if 2 (or more) photons hit the same pixel during one read-out frame the accumulated charge may exceed the limiting value of 3000 adu. Thus this ``event'' will be treated as MIP and this CCD column and the neighbouring ones get rejected in this read-out frame. This causes a spatial inhomogeneity in the exposure (a warning is issued by epframes in this case), and especially the number of recorded out-of-time events is significantly reduced in CCD columns in the core of the PSF (where they are usually strongest).