The Effect of Large Apertures on Atmospheric Noise Spectra for Millimeter-wave Telescopes
Abstract
Ground-based millimeter and submillimeter telescopes produce astronomical maps that contain a combination of noise inherent to themselves as well as contamination from foregrounds, with the strongest foreground being fluctuating atmospheric emission. While the emission of the turbulent atmosphere itself follows a scale-free power law, the atmosphere as seen by the telescope is modified by the properties of the instrument optics. A naive power-law extrapolation of the atmospheric noise spectrum ignores the blurring effect of the near-field beam, which becomes more pronounced for larger telescope apertures and at higher multipoles. In this work, we use a toy model to derive a semianalytic estimate of the atmospheric noise spectrum that takes into account the effects of near-field optics. We show that it has an appreciable effect for large-aperture telescopes, suggesting that ultra-sensitive, high-resolution experiments are not necessarily limited by the atmosphere on small angular scales. We also present an estimate of the atmospheric knee as a function of the primary aperture, the atmospheric scale height, and the outer scale of turbulence.
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BibTeX
@misc{morris2026effect,
title = {{The Effect of Large Apertures on Atmospheric Noise Spectra for Millimeter-wave Telescopes}},
author = {Thomas W. Morris and Neelima Sehgal},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.41252},
eprint = {2610.41252},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.41252},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Effect of Large Apertures on Atmospheric Noise Spectra for Millimeter-wave Telescopes
AU - Thomas W. Morris
AU - Neelima Sehgal
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2610.41252
UR - https://arxiv.org/abs/2610.41252
AB - Ground-based millimeter and submillimeter telescopes produce astronomical maps that contain a combination of noise inherent to themselves as well as contamination from foregrounds, with the strongest foreground being fluctuating atmospheric emission. While the emission of the turbulent atmosphere itself follows a scale-free power law, the atmosphere as seen by the telescope is modified by the properties of the instrument optics. A naive power-law extrapolation of the atmospheric noise spectrum ignores the blurring effect of the near-field beam, which becomes more pronounced for larger telescope apertures and at higher multipoles. In this work, we use a toy model to derive a semianalytic estimate of the atmospheric noise spectrum that takes into account the effects of near-field optics. We show that it has an appreciable effect for large-aperture telescopes, suggesting that ultra-sensitive, high-resolution experiments are not necessarily limited by the atmosphere on small angular scales. We also present an estimate of the atmospheric knee as a function of the primary aperture, the atmospheric scale height, and the outer scale of turbulence.
ER -