arXiv subjects

J. Treuttel

Publications and source records attributed to J. Treuttel.

4 recordsLinked to original sources

arXiv2026

Proof of concept of the COSMOCal project at the IRAM 30m telescope

This work reports on a test campaign conducted at the IRAM 30m telescope to validate the COSMOCal instrument, a novel concept for absolute calibration of polarization angle, beam properties, and instrumental efficiency. The development is motivated by the stringent calibration requirements of current and next-generation Cosmic Microwave Background (CMB) experiments, whose goal is the precise measurement of CMB polarization. Such measurements are essential to probe fundamental physics, including the possible imprint of primordial inflation. The COSMOCal concept is designed as a space-borne calibration reference intended to provide a stable and absolute polarized signal observable simultaneously by multiple large-aperture ground-based observatories. Prior to any space deployment, a terrestrial prototype was developed and characterized in the laboratory, as reported in Ritacco et al. 2024. The results presented here describe the first validation of the system coupled to an antenna, carried out at the IRAM 30m telescope in September 2024. This campaign aimed at assessing the performance of the full instrument under realistic observational conditions, including its ability to reconstruct polarization observables and interface with a state-of-the-art millimeter-wave polarimeter.

astro-ph.IM↗

arXiv2026

Status of the COSmological Microwave Observations CALibrator

As the sensitivity of CMB telescopes increases, the need for precise calibration becomes critical. Started in 2022, the COSMOCal project aims to place an artificial polarized source in geostationary orbit, which will serve as a reference for CMB telescopes. This source will emit at 90, 150 and 270 GHz and will be linearly polarized with a highly precise orientation smaller than 0.1 deg. This proceeding presents the scientific motivations for the project, the current status of the development of the instrument and the results of a calibration campaign performed in March 2026 at the Institut d'Astrophysique Spatiale.

astro-ph.IM↗

arXiv2024

Absolute reference for microwave polarization experiments -- The COSMOCal project and its proof of concept

The cosmic microwave background (CMB), a remnant of the Big Bang, provides unparalleled insights into the primordial universe, its energy content, and the origin of cosmic structures. The success of forthcoming terrestrial and space experiments hinges on meticulously calibrated data. Specifically, the ability to achieve an absolute calibration of the polarization angles with a precision of < 0.1 deg is crucial to identify the signatures of primordial gravitational waves and cosmic birefringence within the CMB polarization. We introduce the COSMOCal project, designed to deploy a polarized source in space for calibrating microwave frequency observations. The project aims to integrate microwave polarization observations from small and large telescopes, ground-based and in space, into a unified scale, enhancing the effectiveness of each observatory and allowing robust combination of data. To demonstrate the feasibility and confirm the observational approach of our project, we developed a prototype instrument that operates in the atmospheric window centered at 260 GHz, specifically tailored for use with the NIKA2 camera at the IRAM 30 m telescope. We present the instrument components and their laboratory characterization. The results of tests performed with the fully assembled prototype using a KIDs-based instrument, similar concept of NIKA2, are also reported. This study paves the way for an observing campaign using the IRAM 30m telescope and contributes to the development of a space-based instrument.

astro-ph.CO↗

arXiv2023

Polarization angle accuracy for future CMB experiments. The COSMOCal project and its prototype in the 1mm band

The Cosmic Microwave Background (CMB) radiation offers a unique window into the early Universe, facilitating precise examinations of fundamental cosmological theories. However, the quest for detecting B-modes in the CMB, predicted by theoretical models of inflation, faces substantial challenges in terms of calibration and foreground modeling. The COSMOCal (COsmic Survey of Millimeter wavelengths Objects for CMB experiments Calibration) project aims at enhancing the accuracy of the absolute calibration of the polarization angle $\psi$ of current and future CMB experiments. The concept includes the build of a very well known artificial source emitting in the frequency range [20-350] GHz that would act as an absolute calibrator for several polarization facilities on Earth. A feasibility study to place the artificial source in geostationary orbit, in the far field for all the telescopes on Earth, is ongoing. In the meanwhile ongoing hardware work is dedicated to build a prototype to test the technology, the precision and the stability of the polarization recovering in the 1 mm band (220-300 GHz). High-resolution experiments as the NIKA2 camera at the IRAM 30m telescope will be deployed for such use. Once carefully calibrated ($\Delta\psi$ < 0.1 degrees) it will be used to observe astrophysical sources such as the Crab nebula, which is the best candidate in the sky for the absolute calibration of CMB experiments.

astro-ph.IM↗