POLarization Orientation CALibrator for Cosmology

I will enable groundbreaking results for cosmology and fundamental physics, thanks to a novel method for measuring the angle of the polarization plane of the Cosmic Microwave Background (CMB) photons with unprecedented accuracy.

Existing and planned CMB polarimeters looking for primordial B-mode signals need an independent, experimental method for systematics control on the absolute polarization orientation.

The lack of such a method limits the accuracy of the detection of inflationary gravitational waves, the efficiency in removing polarized foregrounds, the constraining power on the neutrino sector through measurements of gravitational lensing of the CMB, the possibility of detecting Cosmic Birefringence, and the ability to measure primordial magnetic fields.My 5-year project will dramatically improve instrumental accuracy by means of artificial calibration sources flying on aerial drones and tethered balloons, within sight of the most advanced ground CMB telescopes, operating at high-elevation angles and far-field distances.

The calibrators will make use of linearly-polarized microwave emitters optimally coupled to the Simons Observatory (SO) polarization-sensitive detectors, the world-leading CMB project for the next decade.

The orientation of the source polarization plane will be registered to absolute celestial coordinates by star cameras and ground photogrammetry with arcminute accuracy. POLOCALC will take advantage of my leading role in SO, and will operate from its site in the Atacama Desert in Chile.

This project will become a pivot for the field: any existing or future instrument in Atacama will be able to observe my novel polarization calibrator, and future projects will intercalibrate their detectors with the resulting calibrated observations of sky sources.

POLOCALC will produce the first experimentally-calibrated data of the polarization angle of the CMB and its contaminants, allowing existing and future CMB polarimeters to fully mine the cosmic sky.