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: http://xmm.vilspa.esa.es/sas/7.1.0/doc/arfgen/node24.html
Дата изменения: Thu Nov 15 16:15:38 2007 Дата индексирования: Sat Dec 22 08:41:25 2007 Кодировка: Поисковые слова: south pole |
The performance of arfgen
depends mainly on the
number of points in the detector map that are enclosed
within the said regions.
This means that the
coarser the detector map, the less CAL calls are made,
and the less accurate the resultant ARF is. At the other
extreme, a detector map that is too finely binned would result
in a large number of CAL calls and would affect the execution
time of the task. Ideally the binning should be such that it
reflects the spatial scaling of instrumental variations across
the detector. The current version of this task does not
have any feature that varies at scales smaller
than 1 arcmin,
so the user is recommended to use detector maps with
bin sizes around this value. Once pile-up effects
are accounted for by this task,
the bin size for the detector map
would have to be much smaller in order
to oversample the PSF (
arcseconds).
It is expected in such cases the user would
mostly be interested in a single point source,
so the total area enclosed by all the regions,
and thus the number of points in the (filtered)
detector map, should be relatively low.
The execution time is also dependent upon the actual size of the source region if chip gap and bad pixel corrections are switched on (withbadpixcorr=true). In fact this becomes the dominant contribution for large source areas.
XMM-Newton SOC/SSC -- 2007-11-15