Orateur
Description
One of the main challenges of the next generation of cosmic microwave background (CMB) experiments is probing the primordial gravitational waves signal that have left an imprint in the curly pattern (a.k.a B -modes) of the CMB polarization. This very weak signal, if detected, will probe the existence of the inflation era and open the path to a physics beyond the standard model.
This goal has motivated a huge technological effort to reach an unprecedented level of instrument sensitivity. However, the most limiting factors nowadays are: i) high control of instrumental systematics; ii) absolute calibration of polarization angle and iii) removal of foreground emissions. In this context, recent findings (Ritacco et al. 2023 ) have shown that important information is still lacking for the correct reconstruction of the spectral energy distribution of foreground dust in polarization signals E and B, which could therefore, if not correctly interpreted, significantly bias the CMB signal. The presentation aims at presenting these latest results that drive the motivations of a project idea, called COSMOCal, to deliver a model and instrument independent method to ensure the absolute calibration of CMB experiments with the accuracy required to probe CMB B-modes and the cosmic birefringence. This project consists on building an artificial calibration source to be mounted on a nanosatellite placed in geostationary orbit and to be used for the self calibration of ground-based telescopes. We are currently building the first prototype to be tested at IRAM 30m telescope with the NIKA2 camera. I will present the scientific motivations for this project together with the technical challenges and the status of the prototype construction.
