The telescope calibration will supply, as a function of off-axis angle and azimuthal angle, the effective area vs. energy and the beam profile vs. energy. These are not expected to vary with time. Other calibrations--to be performed in-flight--include the thermal expansion of the optical bench due to the day/night cycle, the effects of scattered X-rays from the Sun and from the bright Earth.
The first of the four X-ray telescopes has been tested optically at Nagoya University and is being tested currently in the ISAS X-ray beam facility.