XMM-Newton Science Analysis System


attcalc (attcalc-4.39) [xmmsas_20230412_1735-21.0.0]

Algorithm

   subroutine attcalc

     * get input events
     * get instrument, mode and ccdid from events file
     * add X/Y columns to event table if they don't already exist

     * obtain CCF, set state 

     * get refpointlabel (source of reference point information) 
     * get RA\_PNT, DEC\_PNT and PA\_PNT from atthkset (atthkgen output file)
         if no file, use NOM values
     * set central reference point (nominalra, nominaldec)
     * get attitudelabel (source of attitude information)
     * if attitudelabel=fixed, get fixedra, fixeddec, fixedposangle
     * if attitudelabel=ahf or om, set attitudeFromAhf (AHF or OM)

     * loop through events
         if event time has changed (i.e. is frame different) then 
           if (attitudelabel .ne. fixed) then 
             call OAL_getAttitude  (AHF/OM attitude information)     
             identify if special case (e.g. dec=0, +90, -90) 
             transform from spherical to parallel coords
             repeat above for a point 1 degree more north along the local meridian 
               (the `help point'), to get the angle with the nominal meridian
           endif
           call getBoresightMatrix and apply boresight correction
         endif 
         apply corrected attitude information to event DETX/DETY to get X/Y
     * end loop through events   

     * add WCS parameters to events file
     * (calculation of and) adding of keywords to event file
     * add history to events file

   end subroutine attcalc