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оригинального документа
: http://xmm.vilspa.esa.es/sas/7.1.0/doc/omlcbuild/node8.html
Дата изменения: Mon Jul 9 06:09:34 2007 Дата индексирования: Sat Dec 22 11:13:52 2007 Кодировка: Поисковые слова: asteroid |
subroutine omlcbuild
read parameters
loop i=0, nSources
get handle on source rates file
get handle on source region file
if (exposure IDs are different) issue warning
get handle on background rates file
get handle on background region file
if (exposure IDs are different) issue warning
if (exposure ID source != exposure ID background) call fatal
get source extraction radius = s_radius
get CAL coincidence loss correction radius = cal_radius
get photometry radius = ph_radius
calculate the instrumental limiting magnitude from the
detection limit count rate
compute area of source region = s_area
compute area of background region = b_area
tStart = max(tBack[0], tSource[0])
eEnd = min(tBack[nBack-1], tSource[nSource-1]
tDel = (tEnd - tStart)/(nSource-1)
determine the PSF fraction within the source extraction region
determine the PSF fraction within the `background` extraction region
% calculate the ratio between counts inside and outside OSW:
% PSF fraction = sum(PSF inside OSW)/ sum(complete PSF inside s_radius area)
loop i = 0, ntimebins
newTime = tStars + i * tDel
% linear interp to get source rate
linear interp to get background rate for each source bin
% compute background subtracted rate error
compute source rate error
compute background rate error
% scale background counts to the source area:
% backround count rate = background count rate * source area / b_area
% subtract background from the source:
% background subracted rate = source rate - background count rate
% correct source counts for the PSF fraction inside extraction area
% (correction is to value expected within CAL (r=12 pixels) aperture):
% source = source / PSF_fraction
set up equations for counts recorded in each region. These allow
for (point) source contamination of the `background` region:
C(S+B) = PSF(S+B) *S + NPIX(S+B) * Bpix
C(B) = PSF(B) *S + NPIX(B) * Bpix
solve these for S, the source counts over the coincidence loss (CL)
region (ie the CAL aperture) and for Bpix, the background counts
per pixel.
scale background to the CAL aperture area:
bkgnd count rate = background count rate * cal_radius area / s_area
recombine these bkgnd and source rates (now determined for the
CAL aperture)
apply CL correction to the source+bkgnd rate
apply CL correction to the bkgnd rate
CL corrected source rate = source+bkgnd rate - bkgnd rate
correct result for dead time
correct for PSF beyond the 12 pixel Cal aperture (mainly for UV)
end loop
write time keywords to header
write output rates file
release handle
end loop
end subroutine omlcbuild