CIRCULAR SCANS FOR COSMIC MICROWAVE BACKGROUND ANISOTROPY OBSERVATIONAND ANALYSIS

A number of experiments for measuring anisotropies of the cosmic micro wave background (CMB) use scanning strategies in which temperature flu ctuations are measured along circular scans on the sky. It is possible , from a large number of such intersecting circular scans, to build tw o-dimensional sky maps for subsequent, analysis. However, since instru mental effects - especially the excess low-frequency 1/f noise - proje ct on to such two-dimensional maps in a non-trivial way, we discuss th e analysis approach which focuses on information contained in the indi vidual circular scans. This natural way of looking at CMB data from ex periments scanning on the circles combines the advantages of elegant s implicity of Fourier series for the computation of statistics useful f or constraining cosmological scenarios, and superior efficiency in ana lysing and quantifying most of the crucial instrumental effects.