Status and future development of the COSMOCal Project for absolute CMB polarization calibration
Silvia Micheli, Alessia Ritacco, Alessandro Carones, Jonathan Aumont, Stefano Berta, Ludovico Bizzarri, François Boulanger, Andrea Catalano, Francesco Cuttaia, Anne Denis, François-Xavier Désert, Anne Laure Fontana, David González-Ovejero, Benedetta Kalemi, Nicoletta Krachmalnicoff, Samuel Leclercq, Thibaut Louis, Juan-Francisco Macías-Pérez, Bruno Maffei, Tania Mcnamara, Marina Migliaccio, Ludovic Montier, Pascal Morfin, Michel Moulin, Louise Mousset, Matteo Murgia, Ioannis Myserlis, Federico Nati, Pierluigi Ortu, Michel Pérault, Giampaolo Pisano, Tonino Pisanu, Nicolas Ponthieu, Sofia Savorgnano, Luca Terenzi, Jeanne Treuttel, Léo Vacher, Christophe Vescovi, Mario Zannoni
astro-ph.IM, astro-ph.CO
Submitted: 2026-07-14
Comments: Submitted to Proceedings of SPIE, Astronomical Telescopes + Instrumentation 2026. 12 pages, 3 figures
License: http://creativecommons.org/licenses/by/4.0/
The gist: Cosmic Microwave Background (CMB) polarization measurements are pushing instrumental sensitivities to levels where calibration systematics become a dominant limitation.
Terminology
Abstract
Cosmic Microwave Background (CMB) polarization measurements are pushing instrumental sensitivities to levels where calibration systematics become a dominant limitation. The large dynamic range between cosmological and Galactic emission prevents future experiments from relying only on diffuse sky measurements or standard celestial calibrators. To address this challenge, the COSmological Microwave Observations Calibrator (COSMOCal) project proposes an artificial calibration source deployed as a guest payload on a geostationary satellite, scheduled for launch by the Eutelsat group by 2030. This source will provide stable, well-characterized polarized microwave signals accessible to multiple ground-based observatories. In this work, we present the status of the project, the updated development timeline, and the refined scientific and technical requirements, defined with the observatories that plan to use this calibration source. Furthermore, we investigate the interplay between instrumental systematics and component separation in the presence of complex models of interstellar dust emission. We discuss in this paper how this can impact the recovery of the primordial signal, and whether residual calibration errors can degrade the performance of foreground cleaning algorithms.
Sources
- The LiteBIRD mission to explore cosmic inflation
- Cosmic Birefringence from the Atacama Cosmology Telescope Data Release 6
- Absolute calibration of the polarisation angle for future CMB $B$-mode experiments from current and future measurements of the Crab nebula
- BROOM: a python package for model-independent analysis of microwave astronomical data
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