On the dipole straylight contamination in spinning space missions dedicated to CMB anisotropy

We present an analysis of the dipole straylight contamination (DSC) for spinning space-missions designed to measure CMB anisotropies. Although this work is mainly devoted to the {\sc Planck} project, it is relatively general and allows to focus on the most relevant DSC implications. We first study a simple analytical model for the DSC in which the pointing direction of the main spillover can be assumed parallel or not to the spacecraft spin axis direction and compute the time ordered data and map. The map is then analysed paying particular attention to the DSC of the low multipole coefficients of the map. Through dedicated numerical simulations we verify the analytical results and extend the analysis to higher multipoles and to more complex (and realistic) cases by relaxing some of the simple assumptions adopted in the analytical approach. We find that the systematic effect averages out in an even number of surveys, except for a contamination of the dipole itself that survives when spin axis and spillover directions are not parallel and for a contamination of the other multipoles in the case of complex scanning strategies. In particular, the observed quadrupole can be affected by the DSC in an odd number of surveys or in the presence of survey uncompleteness or over-completeness. Various aspects relevant in CMB space projects (such as implications for calibration, impact on polarization measurements, accuracy requirement in the far beam knowledge for data analysis applications, scanning strategy dependence) are discussed.Comment: 21 pages, 13 Figures, 1 Table. To appear in MNRAS. Accepted 2006 July 13. Received 2006 July 13; in original form 2006 June 7. This work has been done in the framework of the Planck LFI activitie

Perspectives for Cosmological Reionization From Future CMB and Radio Projects

In spite of the great recent results from the Planck satellite supporting cosmological reionization scenarios almost compatible with astrophysical models for the evolution of structure, galaxy and star formation, the full understanding of the reionization and thermal history since recombination epoch is still far to be consolidated. The radio to sub-millimeter background provides a very important window for studying cosmological reionization process in a global approach, to arrive to the complete comprehension of the involved photon and energy sources. CMB polarization provides global information of ionization history, 21-cm line tomographic view allows to reconstruct ionization and clumping history, CMB spectral distortion provides global information on these aspects and a direct view of the global energy dissipations. Given the relevance of cosmological reionization for the comprehension of early phases of structure formation and evolution and its connection with a large variety of astrophysical and cosmological questions, it is important to discriminate among the various models compatible with current data. A brief overview of the proposals of future CMB missions and of radio [namely the Square Kilometer Array (SKA) and its precursor/pathfinders] projects is presented. We then describe the scientific outcome of future CMB missions, focussing on the information carried out by polarization anisotropies, spectral (absolute temperature) distortion and dipole (anisotroy) distortions, and discuss the promising perspectives opened by forthcoming and future radio surveys, focussing on the information carried out by the redshifted 21-cm line and by the free-free diffuse emission. Finally, we describe the contribution of future radio surveys to reionization studies with CMB polarization projects

Workshop summary and the future

We present a tentative summary of the many very interesting issues that have been addresses at this workshop, focussing in particular on the perspectives for measuring the polarization power spectra of the Cosmic Microwave Background produced by scalar and tensor perturbations, in the presence of foregrounds.Comment: 8 pages, 3 figures, to appear in S. Cecchini et al., Astrophysical Polarized Backgrounds, AIP Conf. Proceeding