Scanning strategy for mapping the Cosmic Microwave Background anisotropies with Planck

European Space Agency – ESTEC, Astrophysics Division, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands e-mail: xdupac@rssd.esa.int

Received: 24 June 2004
Accepted: 16 September 2004

Abstract

We present simulations of different scanning strategies for the Planck satellite. We review the properties of slow- and fast-precession strategies in terms of uniformity of the integration time on the sky, the presence of low-redundancy areas, the presence of deep fields, the presence of sharp gradients in the integration time, and the redundancy of the scanning directions. We also compare the results obtained when co-adding all detectors of a given frequency channel. The slow-precession strategies allow a good uniformity of the coverage, while providing two deep fields. On the other hand, they do not allow a wide spread of the scan-crossing directions, which is a feature of the fast-precession strategies. However, the latter suffer from many sharp gradients and low-coverage areas on the sky. On the basis of these results, the strategy for Planck can be selected to be a slow (e.g. 4 month-period) sinusoidal or cycloidal scanning.