Fig. 17 shows the SXT CCD. The orientation of the CCD in the figure corresponds to the standard display in IDL in which full-Sun images have Solar-North at the top and East at the left. There is a coordinate system in the figure which is referred to as ``IDL" coordinates, with IDL(0,0) corresponding to the lower left corner (which is nearest the south-east portion of the solar image). The physical read-out of the CCD occurs from North to South (top to bottom) as a parallel transfer into the serial register and then is read out from east to west (or from left to right in the figure). The physical device coordinate system in the figure is referred to as the ``CCD" coordinate system. CCD(0,0) is in the lower right corner (which is nearest the south-west portion of the solar image). Note that CCD(1,0) = IDL(1023,0). This transformation is made automatically by the reformatter (i.e., YODAT returns images already converted to IDL coordinates). Also note that the column corresponding to CCD(0,*) is not included in telemetry. In fact, the on-chip summing is not exactly registered between full-, half-, and quarter- resolution modes. For example, in quarter-resolution, one would expect IDL_Q(0,*) to correspond to in full-resolution IDL_F(0:3,*), but instead it corresponds to IDL_F(3:6,*). For this reason, a simple REBIN or CONGRID function to convert SXT images to a higher or lower resolution will result in a slight mis-alignment. The GT_CORNER and GT_CENTER routines apply the correct shifts corresponding to the various image resolution modes. SXT Calibration Note 35 contains more details about the SXT pixel coordinate system.
Figure 17: SXT CCD Pixel Layout