8-10 September 2021
GMT timezone

Measuring spectral distortions of the CMB: the COSMO experiment

8 Sep 2021, 11:15


Elisabetta Marchitelli (Sapienza, University of Rome)


The COsmic Monopole Observer (COSMO) is a pathfinder, ground-based experiment, designed for the detection of the isotropic $y$-distortion of the Cosmic Microwave Background (CMB). Deviations from a pure blackbody are expected as an evidence of all the interactions that CMB photons undergo along the thermal history of the Universe. Their observation provides an insight into processes involving CMB photons that took place both before and after recombination.The upper limit on the $y$-distortion is still the one from the COBE-FIRAS mission ($y<10^{-5}$) due to the extreme accuracy required for spectral distortions measurements.
COSMO exploits a cryogenic Martin-Puplett Fourier Transform Spectrometer, comparing the radiation collected from the sky to the one from an internal, cryogenic blackbody reference with high emissivity. All the optical elements of the FTS are maintained at a temperature of 2.7 K to minimize instrument emission. The interferogram is obtained modulating the optical path difference (OPD) with cryogenic, frictionless linear motion of one of the two roof-mirrors. The maximum mirror displacement is $\pm 25$ mm, and it is measured with a resolution of $10 \mu $m. This provides a spectral resolution around 5 GHz. A flat spinning wedge mirror, at room temperature, allows to perform fast sky dips along $20^{\circ}$ diameter circle in the sky while scanning the interferogram. This strategy enables to measure and remove most of the atmospheric emission and its slow fluctuations. Fast detectors are required, so small multi-mode Kinetic Inductance Detectors (KIDs) arrays ($\tau \sim 50\mu$s), operating in the 120-280 GHz range, will equip the two focal planes.
COSMO will operate from the Concordia station, at Dome-C, in Antarctica, arguably the best site on Earth for this kind of measurements.

Primary author

Elisabetta Marchitelli (Sapienza, University of Rome)


Elia Stefano Battistelli (Sapienza, University of Rome) Paolo de Bernardis (Dipartimento di Fisica, Sapienza Università di Roma) Prof. Marco Bersanelli (Università degli studi di Milano) Dr Fabio Columbro (Sapienza University of Rome) Mr Gabriele Coppi (Università di Milano Bicocca) Alessandro Coppolecchia (Physics Department, University of Rome Sapienza, P.le Aldo Moro 5, 00185, Roma,Italy) Dr Giuseppe D'Alessandro (Sapienza University of Rome) Prof. Marco De Petris (Sapienza University of Rome) Dr Cristian Franceschet (Università degli studi di Milano) Prof. Massimo Gervasi (Università di Milano Bicocca) Dr Luca Lamagna (Sapienza University of Rome) Mr Andrea Limonta (Università di Milano Bicocca) Ms Elenia Manzan (Università degli studi di Milano) Silvia Masi (Sapienza University, Rome Italy) Lorenzo Mele (Sapienza University of Rome) Prof. Aniello Mennella (Università degli studi di Milano) Dr Federico Nati (Università di Milano Bicocca) Dr Alessandro Paiella (Sapienza University of Rome) Dr Giorgio Pettinari (Istituto di fotonica e nanotecnologie - CNR) Prof. Francesco Piacentini (Sapienza University of Rome) Prof. Lucio Piccirillo (School of Physics and Astronomy - University of Manchester) Prof. Giampaolo Pisano (Sapienza University of Rome) Dr Sabrina Realini (Università degli studi di Milano) Prof. Carole Tucker (Cardiff University) Prof. Mario Zannoni (Università di Milano Bicocca)

Presentation Materials