On the P lanck in - flight antenna beam shape reconstruction using planet transit

An abstract should be given he calibration of the in-flight antenna beam shape and possible beam degradation is one of the most crucial tasks for the upcoming Planck mission. We examine several effects which could significantly act on the in-flight main beam calibration using planet transit: the problems of the variability of Jupiter flux, the antenna temperature and passing of the planets through the main beam. We estimate these effects on the antenna beam shape calibration and calculate the limits on the main beam and far sidelobe measurements, using Jupiter and Saturn. We also discuss possible effects of degradation of the mirror surfaces and specify corresponding parameters which can help us to determine this effect.