Gabriele Coppi, Nadia Dachlythra, Federico Nati, Rolando Dünner-Planella, Alexandre E. Adler, Josquin Errard, Nicholas Galitzki, Yunyang Li, Matthew A. Petroff, Sara M. Simon, Ema Tsang King Sang, Amalia Villarrubia Aguilar, Edward J. Wollack, Mario Zannoni
Coppi et al. (2025)
The Astrophysical Journal Supplement Series 279, 30
Research overview
This paper presents PROTOCALC, a drone-borne polarized calibration source operating in the W-band (~90 GHz) to address the scarcity of bright, naturally polarized celestial calibrators. High-precision polarization angle calibration is essential for cosmic microwave background (CMB) telescopes searching for primordial B-modes and cosmic birefringence.
The 1.75 kg payload—mounted on a DJI Matrice 600 Pro drone—integrates an RF synthesizer and multiplier chain, a wire-grid polarizer, and a photogrammetry camera tracking ground targets for attitude determination. Laboratory characterization demonstrated optical alignment accuracy better than 0.01°, while field deployments in the Atacama Desert targeting the CLASS and Simons Observatory telescopes achieved a mean roll-angle reconstruction accuracy of 0.045°, validating the system’s potential for next-generation CMB experiments such as CMB-S4.
Key findings
- W-band source
- ~90 GHz operating region
- drone deployment
- optical alignment accuracy better than 0.01°
