A Clock Stabilization System for CHIME/FRB Outriggers
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Mena-Parra_2022_AJ_163_48.pdf
Description
Published version
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1.06 MB
Format
Adobe PDF
Checksum (MD5)
a4e2e6c50a8f8ab24a22d974807a2a5a
Author(s)
Mena-Parra, J
Leung, C
Cary, S
Masui, KW
Kaczmarek, JF
Amiri, M
Bandura, K
Boyle, PJ
Cassanelli, T
Cliche, J-F
Date Issued
February 1, 2022
Journal
The Astronomical Journal
Publisher
American Astronomical Society
Citation
Mena-Parra, J, Leung, C, Cary, S, Masui, KW, Kaczmarek, JF et al. 2022. "A Clock Stabilization System for CHIME/FRB Outriggers." The Astronomical Journal, 163 (2).
Version
Final published version
Abstract
Abstract
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has emerged as the prime telescope for detecting fast radio bursts (FRBs). CHIME/FRB Outriggers will be a dedicated very-long-baseline interferometry (VLBI) instrument consisting of outrigger telescopes at continental baselines working with CHIME and its specialized real-time transient-search backend (CHIME/FRB) to detect and localize FRBs with 50 mas precision. In this paper, we present a minimally invasive clock stabilization system that effectively transfers the CHIME digital backend reference clock from its original GPS-disciplined ovenized crystal oscillator to a passive hydrogen maser. This enables us to combine the long-term stability and absolute time tagging of the GPS clock with the short- and intermediate-term stability of the maser to reduce the clock timing errors between VLBI calibration observations. We validate the system with VLBI-style observations of Cygnus A over a 400 m baseline between CHIME and the CHIME Pathfinder, demonstrating agreement between sky-based and maser-based timing measurements at the 30 ps rms level on timescales ranging from one minute to up to nine days, and meeting the stability requirements for CHIME/FRB Outriggers. In addition, we present an alternate reference clock solution for outrigger stations that lack the infrastructure to support a passive hydrogen maser.
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has emerged as the prime telescope for detecting fast radio bursts (FRBs). CHIME/FRB Outriggers will be a dedicated very-long-baseline interferometry (VLBI) instrument consisting of outrigger telescopes at continental baselines working with CHIME and its specialized real-time transient-search backend (CHIME/FRB) to detect and localize FRBs with 50 mas precision. In this paper, we present a minimally invasive clock stabilization system that effectively transfers the CHIME digital backend reference clock from its original GPS-disciplined ovenized crystal oscillator to a passive hydrogen maser. This enables us to combine the long-term stability and absolute time tagging of the GPS clock with the short- and intermediate-term stability of the maser to reduce the clock timing errors between VLBI calibration observations. We validate the system with VLBI-style observations of Cygnus A over a 400 m baseline between CHIME and the CHIME Pathfinder, demonstrating agreement between sky-based and maser-based timing measurements at the 30 ps rms level on timescales ranging from one minute to up to nine days, and meeting the stability requirements for CHIME/FRB Outriggers. In addition, we present an alternate reference clock solution for outrigger stations that lack the infrastructure to support a passive hydrogen maser.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
Massachusetts Institute of Technology. Department of Physics
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Creative Commons Attribution 4.0 International license
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DOI of Published Version
https://doi.org/10.3847/1538-3881/ac397a
