Physical coordinates of some non-Chandra data sets are not read.
If a FITS image file which specifies "POS" as the transform for physical coordinates is read into Sherpa with load_image, its physical coordinates will not be read, as "sky" is expected. Viewing the image with image_data in Sherpa will show that the image and physical coordinates are identical, whereas viewing the image in DS9 directly from the Unix command line will show that they do differ. This is a bug which will be fixed in the next release of Sherpa.
Note that an attempt to change to the physical coordinate system from the default image coordinate system will result in an error:
sherpa> load_image("xmm_bin50.fits") sherpa> get_coord() 'logical' sherpa> set_coord("physical") DataErr: data set 'xmm_bin50.fits' does not contain a physical coordinate system