  Angular power spectrum of the cosmic microwave background (CMB) temperature
anisotropies is one of the most important on characteristics of the Universe
such as its geometry and total density. Using flat sky approximation and
Fourier analysis, we estimate the angular power spectrum from an ensemble of
least foreground-contaminated square patches from WMAP W and V frequency band
map. This method circumvents the issue of foreground cleaning and that of
breaking orthogonality in spherical harmonic analysis due to masking out the
bright Galactic plane region, thereby rendering a direct measurement of the
angular power spectrum. We test and confirm Gaussian statistical characteristic
of the selected patches, from which the first and second acoustic peak of the
power spectrum are reproduced, and the third peak is clearly visible albeit
with some noise residual at the tail.
