Speaker
Description
Of the six ΛCDM parameters, five are constrained to percent level or lower by Planck data. The constraints on the optical depth to reionisation τ, are however ten times looser. Indeed, τ is almost fully degenerate with the primordial power spectrum amplitude As. Breaking the degeneracy between As and τ is important for several cosmological challenges, including measuring the sum of neutrino masses. Thanfully, in CMB polarisation spectra, the degeneracy is lifted at very large angular scales on the sky (>10°). Accurate measurements of CMB polarisation on those scales require an experiment with a very wide sky coverage. In this talk, I will present Taurus, a stratospheric balloon experiment that should observe the polarized microwave sky for a month in four frequency bands between 150 and 350 GHz. Its launch is scheduled from New Zealand in the mid 2020s. Results from Taurus should greatly the uncertainty on τ and be complementary with other upcoming CMB experiments, like CMB-S4.
