XMM-Newton Science Analysis System


omatt (omatt-2.58) [xmmsas_20230412_1735-21.0.0]

Algorithm

subroutine omatt

   open output file
   read the OSW window parameters, binning factors from header

   call CAL_GetBoresightMat
   call OAL_GetAttitude (with time of reference frame)

   find OM boresight direction
   rotate by roll angle

   loop over individual source information
      read in individual source information
      extract pixel position
      correct for distortion (CAL_omDistortion)
      call to CAL_omPlatescale to get linear plate-scale 
      perform co-ordinate conversion
      (including s/c boresight offset correction and roll angle) 
   end loop
   Add columns for the RA and dec of each source to the source-list file.

   if (usecat) then
       read in the catalogue data.
       Set up a grid of offsets deltax and deltay in the x and y directions.
       Sort these offsets into increasing radius order from the origin.
       For each grid shift the stars by deltax and deltay in the x
       and y directions. 
       Try to match each star with one in the catalogue by computing the
       distance between it and the selected catalogue stars and regarding 
       it as matched if the distance is less than the specified tolerance.
       For each pair of offsets compute a maximum-likelihood parameter and take
       the pair with the maximum value as the best offsets. 
       Use these offsets to repeat the star matching, and then perform a
       least-squres fit to improve the offsets and also determine any small
       rotation between the two coordinate systems.
       Determine errors on the computed parameters by a Monte Carlo procedure 
       which generates artificial data sets from the original, computes the
       parameters for each simulation, and then at the end computes the mean and
       standard deviations of all the parameters.
       Correct the RAs and Dec of the sources using the computed paramters.
       Added corrected RA and Dec columns to the source-list file, and also
       information about the fit.   

   end if


   Rebin, rotate and correct for distortion the image, and write out to a fits file.
   Rebin, rotate and correct for distortion the 16-bit QUALITY image, and write out to the same fits file.



   close OSWSL
   close output file

end subroutine  omatt