Methods for the pointing reconstruction of the Planck satellite

In this paper we present a method to reconstruct the position of the line of sight and orientation of the focal plane of the Planck satellite, which may be expressed by the parameters of the effective boresight and roll angles, respectively. The accuracy to which these parameters must be determined to avoid compromising the reconstruction of the C-l power spectrum is assessed. It is expected that the pointing reconstruction will be performed using point- source transits in the highest frequency channels, given their smaller beam sizes. Estimates are made for the number of galactic and extragalactic point sources visible by Planck in these channels. The ability of the method presented here to reconstruct the pointing parameters to the required accuracies using these point sources is investigated. It is found that the scanning strategy employed and the actual orientation of the focal plane both independently influence the available number of suitable point sources, from which this method may successfully evaluate the pointing parameters. While this paper focuses on the pointing reconstruction of the Planck satellite, elements of the analysis presented here may be of use elsewhere.