The Simons Observatory: Frequency-resolved beam calibration for the SO SATs with POLOCALC
Abstract
We present a far-field beam calibration of the Simons Observatory (SO) Small Aperture Telescopes (SATs) using scanned single-frequency measurements of a drone-mounted source emitting in the 90 GHz band, where the SATs have an angular resolution of ∼30'. We then compare the results from two campaigns in April and December 2025 to the band-averaged beams from planet observations by the SATs. Measuring the telescope beam response at different frequencies across the observing bands enables modeling the system's frequency-dependent behavior. This helps track optical non-idealities. The comparison with planet beams informs the frequency resolution necessary to accurately reconstruct the band-averaged beams in this way; it uses only the average drone and planet products, as it is intended to demonstrate the feasibility of the frequency-resolved calibration scheme rather than to set the precise beam covariance and instrument requirements. We find that the beams of the two SATs near 90 GHz follow the frequency scaling expected for diffraction-limited optics, with only modest deviations observed in the nearest lobes of one telescope. We establish consistency between the real band-averaged planet beams and the synthesized drone band-averaged beams for the center wafers of both telescopes, with an average deviation smaller than 4% for multipoles ℓ < 500.
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BibTeX
@misc{dachlythra2026simons,
title = {{The Simons Observatory: Frequency-resolved beam calibration for the SO SATs with POLOCALC}},
author = {Nadia Dachlythra and Gabriele Coppi and Ludovico Bizzarri and Federico Nati and Alessandro Novelli and Elle C Shaw and Samuel Day-Weiss and Federico Astori and Susanna Azzoni and Dillon J Bass and Artem Basyrov and Federico Cacciotti and Rolando Dünner Planella and Nicholas Galitzki and Remington Gerras and John C Groh and Jon E Gudmundsson and Saianeesh K Haridas and Kathleen Harrington and Carlos Hervías-Caimapo and Bradley R Johnson and Brian Keating and Adrian T Lee and Anto I Lonappan and Noemi Mezzanzanica and Lyman Page and Giulia Rancati Cattaneo and Sara M Simon and Thierry Souverin and Yoshinori Sueno and Edward J Wollack and Kyohei Yamada and Mario Zannoni.},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.15913},
eprint = {2610.15913},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05829993v1},
}
RIS
TY - UNPB
TI - The Simons Observatory: Frequency-resolved beam calibration for the SO SATs with POLOCALC
AU - Nadia Dachlythra
AU - Gabriele Coppi
AU - Ludovico Bizzarri
AU - Federico Nati
AU - Alessandro Novelli
AU - Elle C Shaw
AU - Samuel Day-Weiss
AU - Federico Astori
AU - Susanna Azzoni
AU - Dillon J Bass
AU - Artem Basyrov
AU - Federico Cacciotti
AU - Rolando Dünner Planella
AU - Nicholas Galitzki
AU - Remington Gerras
AU - John C Groh
AU - Jon E Gudmundsson
AU - Saianeesh K Haridas
AU - Kathleen Harrington
AU - Carlos Hervías-Caimapo
AU - Bradley R Johnson
AU - Brian Keating
AU - Adrian T Lee
AU - Anto I Lonappan
AU - Noemi Mezzanzanica
AU - Lyman Page
AU - Giulia Rancati Cattaneo
AU - Sara M Simon
AU - Thierry Souverin
AU - Yoshinori Sueno
AU - Edward J Wollack
AU - Kyohei Yamada
AU - Mario Zannoni.
PY - 2026
DA - 2026/10/11
PB - HAL
DO - 10.48550/arxiv.2610.15913
UR - https://hal.science/hal-05829993v1
AB - We present a far-field beam calibration of the Simons Observatory (SO) Small Aperture Telescopes (SATs) using scanned single-frequency measurements of a drone-mounted source emitting in the 90 GHz band, where the SATs have an angular resolution of ∼30'. We then compare the results from two campaigns in April and December 2025 to the band-averaged beams from planet observations by the SATs. Measuring the telescope beam response at different frequencies across the observing bands enables modeling the system's frequency-dependent behavior. This helps track optical non-idealities. The comparison with planet beams informs the frequency resolution necessary to accurately reconstruct the band-averaged beams in this way; it uses only the average drone and planet products, as it is intended to demonstrate the feasibility of the frequency-resolved calibration scheme rather than to set the precise beam covariance and instrument requirements. We find that the beams of the two SATs near 90 GHz follow the frequency scaling expected for diffraction-limited optics, with only modest deviations observed in the nearest lobes of one telescope. We establish consistency between the real band-averaged planet beams and the synthesized drone band-averaged beams for the center wafers of both telescopes, with an average deviation smaller than 4% for multipoles ℓ < 500.
ER -