Thermal design and preliminary performance evaluation of the cooling system for BaR-SPOrt

BaR-SPOrt is an experiment to measure the linearly polarized emission of 20°×20° sky patches at 32 GHz and 90 GHz from a stratospheric balloon. It consists of correlation polarimeters for direct measurements of the Q and U Stokes parameters, coupled to an optics providing a beam of 0°.5 (32 GHz) and 0°.2 (90 GHz). Its aim is the study of the polarization of the Diffused Galactic Background as well as the Cosmic Microwave Background Radiation (CMBR). The instrument thermal design and the preliminary performance evaluation of the cooling system are described.