The principal SIS calibrations are the Gain, Charge Transfer Efficiency (CTE), Quantum Efficiency (QE), Read-out Noise and Energy Resolution. These are combined to produce the Response.
It is anticipated that the energy resolution of the SIS may vary with time during the mission. Bombardment by protons trapped in the radiation belts causes the CTE of the CCDs to deteriorate gradually. Once this effect has been quantified in orbit by observing cosmic calibration sources, software which consults the latest calibration data will be distributed to GOs to enable them to make the appropriate modifications to the laboratory-measured SIS response.
The calibration of the flight model SIS cameras have begun at MIT and will continue until they are taken to ISAS for the final integration test in May 1992. A spare SIS camera will be calibrated at White Sands in August 1992 with a spare X-ray telescope.