Abstract : The cosmic microwave background centaine much information about the universe when it vas young, a few hundred. thousand years after the Big-Bang. The statistical analysis of its temperature and polarization fluctuations permits us te mosanes cosmological parameters and te constrain theories of the primordial universe. Moreover, polarisation gives direct accuse; te primordial gravity waves.
The first part of this thesis prescrits the standard model of cosmology and, more specifically, the polarization of the cosmic microwave background.
The polarized signal is not expected te be more than 10% of the temperature fluctuations and should be detected at a level of the order of a few micro-Kelvin. To achieve this sensitivity we can use cooled bolometers coupled to polarizers I show that there exist optimized configurations of the detectors in the focal plane of the instrument which lead to a minimal error box volume; these configurations also ensure that the errors on the Stokes parameters (used te quantify the polarization) are rot correlated.
The main sources of noise in these measurements come from thermal fluctuations, electronics, gain instabilities and optics. These processes lead to important low frequency drifts which significantly reduce the sensitivity of the experiment. I prescrit a simple method which allows us to efficiently remove these drifts; this method uses the redundancies provided by the scanning strategy of the instrument. The results show that the low frequency noise can be removed down to the white noise level.
The last part of this thesis is dedicated to a preliminary analysis of the COSMOSOMAS experiment. The goal of this experiment is to map the polarized emission of the galaxy and the cosmic microwave background fluctuations.