COSMOCal
COSmological Microwave Observations Calibrator
Embedded Files
Sky image of CMB polarization from Planck (ESA)
Scientific motivation
Inflation, a period of rapid expansion in the early universe, is the dominant theoretical framework for elucidating the origin of the structures traced by Cosmic Microwave Background (CMB) anisotropies and which ultimately led to the formation of stars and galaxies. The CMB exhibits two primary polarization patterns: i) the E-modes, characterized by coherent and symmetrical signals originating from density fluctuations in the early universe, and ii) B-modes, in which the CMB polarization display a curl-like pattern on the sky. CMB B-modes provide a unique opportunity to test the cosmic inflation paradigm by detecting the signature (“primordial B-modes”) of primordial gravitational waves. Future CMB observations will also significantly improve our capability to detect cosmic birefringence, which may be caused by very light axions linked to electromagnetism, or primordial magnetic fields, thus creating new opportunities to explore fundamental physics and the essence of dark matter and dark energy.
Project goal
The drive for greater sensitivity to CMB polarization has led to major advances in microwave instrumentation but the promise of future CMB experiments will not simply come from more sensitive experiments, because the high dynamic range of the cosmological and Galactic sky emission makes data calibration a major challenge. It is essential to correct systematics that limit the precision with which sky emission can be separated into cosmological and galactic E and B modes. In particular, the absolute calibration of polarization angles and the characterization of telescope beams is critical.
In a competitive international context, several teams are developing artificial sources positioned on the ground or on drones to calibrate small telescopes at CMB observatories. For large microwave telescopes, the calibration source must be located in space so as to be in the far field. The aim of COSMOCal is to meet this requirement. COSMOCal will make a timely contribution to a key area of observational cosmology, in phase with the deployment of ambitious ground-based CMB experiments in Chile and at the South Pole, and in the next decade with the launch of the LiteBIRD space mission.
Institutional support
Contact: A. Ritacco (alessia.ritacco@lpsc.in2p3.fr), P. Morfin (pascal.morfin@ens.fr) & F. Boulanger (francois.boulanger@ens.fr)
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