Orateur
Description
In the context of future experiments measuring the polarization of the Cosmic Microwave Background (CMB), COSMOCal proposes a method independent of laboratory calibration of CMB instruments and cosmological model assumptions to calibrate next-generation millimeter-wave telescopes. The primary objective is to achieve polarization angle calibration with a precision better than 0.1 degrees. This absolute calibration, required for accurate measurements of CMB B-modes according to leading inflationary models, may also enable an unbiased detection of Cosmic Birefringence by disentangling instrumental effects from the physical process naturally converting E-modes into B-modes.
The key challenge is to distinguish between E and B modes in the CMB and the Galactic foreground emissions, requiring precise control over E-to-B leakage. COSMOCal’s ambition extends beyond absolute angle calibration: deploying an artificial, well-characterized calibration source in the sky enables the study and mitigation of instrumental systematics in ground-based telescopes, including beam distortions and polarization efficiency.
The selected telescopes for this project are so far the IRAM 30m telescope, the Sardinia Radio Telescope (SRT), and the Simons Observatory LAT. Once these telescopes are accurately calibrated, they will observe astrophysical sources to create a catalog of standard candles for other telescopes operating in the same frequency range, both terrestrial and space-based. This will allow the cross-calibration of different data sets. The COSMOCal prototype was successfully tested at the IRAM 30m telescope in October 2024.
This presentation will provide an overview of the COSMOCal project, detailing its goals and outlining the future development roadmap.
