Abstract
Destriping methods for constructing maps of the Cosmic Microwave Background (CMB) anisotropies have been investigated extensively in the literature. However, their error properties have been studied in less detail. Here we present an analysis of the effects of destriping errors on CMB power spectrum estimates for Planck-like scanning strategies. Analytic formulae are derived for certain simple scanning geometries that can be rescaled to account for different detector noise. Assuming {Planck-like low-frequency noise, the noise power spectrum is accurately white at high multipoles (l<50). D estriping errors, though dominant at lower multipoles, are small in comparison to the cosmic variance. These results show that simple destriping map-making methods should be perfectly adequate for the analysis of Planck data and support the arguments given in an earlier paper in favour of applying a fast hybrid power spectrum estimator to CMB data with realistic `1/f' noise.
Highlights
The problem of constructing a map of the CMB anisotropies from a set of time-ordered data (TOD) has been studied by many authors
The TOD can be averaged on rings and the effects of low frequency noise noise approximated by a constant offset for each ring
We have presented an analytic analysis of the effects of destriping errors on the CMB power spectrum for various scanning strategies
Summary
The problem of constructing a map of the CMB anisotropies from a set of time-ordered data (TOD) has been studied by many authors. A brute force application of ‘optimal’ methods requires the inversion of large matrices and is computationally impractical for large TODs such as those expected from WMAP and Planck⋆. Iterative algorithms have been developed (e.g. Wright et al 1996; Natoli et al 2001; Dore et al 2001) which do not require matrix inversions. For Planck-sized datasets, these iterative algorithms are computationally expensive and require the use of supercomputers. Destriping algorithms are well suited to a Planck-type scanning strategy in which the sky is scanned many times on rings. Even for Planck-sized TODs it is practical to apply destriping map making methods on many thousands of simulations to test the effects of various systematic errors (see e.g. Poutanen et al 2004)
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