Analytic Approximations of Scattering Effects on Beam Chromaticity in 21‐cm Global Experiments
Name
Radio Science - 2022 - Rogers - Analytic Approximations of Scattering Effects on Beam Chromaticity in 21‐cm Global.pdf
Description
Published version
Size
377.6 KB
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Adobe PDF
Checksum (MD5)
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Author(s)
Rogers, Alan EE
Barrett, John P
Bowman, Judd D
Cappallo, Rigel
Lonsdale, Colin J
Mahesh, Nivedita
Monsalve, Raul A
Murray, Steven G
Sims, Peter H
Date Issued
November 30, 2022
Journal
Radio Science
Publisher
American Geophysical Union
Citation
Rogers, A. E. E., Barrett, J. P., Bowman, J. D., Cappallo, R., Lonsdale, C. J., Mahesh, N., et al. (2022). Analytic approximations of scattering effects on beam chromaticity in 21-cm global experiments. Radio Science, 57, e2022RS007558.
Version
Final published version
Abstract
Scattering from objects near an antenna produce correlated signals from strong compact radio sources in a manner similar to those used by the “Sea Interferometer” to measure the radio source positions using the fine frequency structure in the total power spectrum of a single antenna. These fringes or ripples due to correlated signal interference are present at a low level in the spectrum of any single antenna and are a major source of systematics in systems used to measure the global redshifted 21‐cm signal from the early universe. In the Sea Interferometer a single antenna on a cliff above the sea is used to add the signal from the direct path to the signal from the path reflected from the sea thereby forming an interferometer. This was used for mapping radio sources with a single antenna by Bolton and Slee in the 1950s. In this paper we derive analytic expressions to determine the level of these ripples and compare these results in a few simple cases with electromagnetic modeling software to verify that the analytic calculations are sufficient to obtain the magnitude of the scattering effects on the measurements of the global 21‐cm signal. These analytic calculations are needed to evaluate the magnitude of the effects in cases that are either too complex or take too much time to be modeled using software.
MIT Department
Haystack Observatory
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DOI of Published Version
https://doi.org/10.1029/2022rs007558
