TABLE 9
                In-flight calibration methods

Item                     Method
Dark current             Shutter closed
Dark current dependence  Shutter closed, varying
on temperature           instrument heater parameters
Geometric distortion     Observation of star fields
Co-alignment             Observation of specific stars
Flat-fielding            Door closed, calibration lamps
                         on,
                         comparison with ground-based
                         data, or
                         smeared exposure on extended
                         sources
Linearity                Multiple exposures at different
                         exposure times
Point spread function    Star observations
Relative spectral        Solar analogue stars and solar
response                 system objects
Absolute calibration     Standard star observations