  The pn camera of EPIC is inherently robust against radiation damage effects.
Nevertheless, the knowledge of charge transfer inefficiency (CTI) of the pn
camera is crucial for obtaining the correct energy scale. We describe detailed
in-orbit monitoring of this effect, utilizing the internal calibration source.
We find that during the first two years in orbit the CTI increased by about 4%
for Al-K and by about 7% for Mn-K. The increases in the CTI are well within
expectations, with no measurable effect on the energy resolution.
