The HXT aspect sensor (HXA) consists of two 1-dimensional CCD arrays located in a cross, 90 degrees to each other. The cross is rotated approximately 45 degrees relative to the SXT and HXT coordinate system. The HXA values are used by the IDL software which creates the attitude (ATT) database. There are fiducial marks which can reduce the resolution of the HXA results if the limb coincides with the fiducial mark.