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: http://xmm.vilspa.esa.es/sas/7.0.0/doc/evproject/node5.html
Дата изменения: Thu Jun 29 00:06:07 2006 Дата индексирования: Sat Dec 22 10:43:58 2007 Кодировка: Поисковые слова: п п п п п п п п |
The task evproject does three things:
These X and Y coordinate values are stored as 4-byte integers in columns of the event list designated by the parameters xcol and ycol. The coordinates are both offset and scaled, the relevant information being stored according to the usual World Coordinate System conventions in WCS column attributes of the xcol and ycol columns. The scaling is such that an increment of 1 in either X or Y value corresponds to a tangent-plane distance equal to the arc length of 0.05 arcsec (same as for the DETX and DETY columns of the event list).
Note that the basic purpose of this projection is to make it easy to extract several images from different selections of the same events. Since the positions of all events on a projection plane are pre-calculated by evproject, it is a simple matter to rebin these positions to form an image. In formal terms, the X and Y values already constitute an image, albeit with a very small pixel size.
Note that the task can either perform this attitude binning itself (with the option to store the result in outbinnedattset) or it can make use of a binning scheme already prepared by task attbin. See section 3.4 for details.
These activities are described in more detail in the remaining subsections of section 3.
XMM-Newton SOC/SSC -- 2006-06-28