WELLARD lets the user specify a region on an image by selecting a shape from a menu and setting its extent using the cursor. A textfile containing the shapes selected is produced. You may select as many shapes as you like, however, you should heed the WARNING item. The initial menu displayed by WELLARD, contains the simple shapes, box, circle and annulus, a QUIT button (which means exit and save the ARD file), and an XRT button.
The XRT button produces a further menu with buttons to write the PSPC rib structure into the file or include sources found by PSS. The latter calculates the radius of a circle at the off-axis angle of the source which will include 95% of the source counts (at an energy of 0.2 keV), this uses the PSF determination calculated by I.Georgantopolous. A circle of this radius is then written into the ARD file.