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Charging of free-falling test masses in orbit due to cosmic rays: Results from LISA Pathfinder


Abstract

A comprehensive summary of the measurements made to characterize test-mass charging due to the space environment during the LISA Pathfinder mission is presented. Measurements of the residual charge of the test mass after release by the grabbing and positioning mechanism show that the initial charge of the test masses was negative after all releases, leaving the test mass with a potential in the range from −12 to −512. Variations in the neutral test-mass charging rate between 21.7 and 30.7  e s$^{−1}$ were observed over the course of the 17-month science operations produced by cosmic ray flux changes including a Forbush decrease associated with a small solar energetic particle event. A dependence of the cosmic ray charging rate on the test-mass potential between −30.2 and −40.3  e s$^{−1}$ V$^{−1}$ was observed resulting in an equilibrium test-mass potential between 670 and 960 mV, and this is attributed to a contribution to charging from low-energy electrons emitted from the gold surfaces of the gravitational reference sensor. Data from the onboard particle detector show a reliable correlation with the charging rate and with other environmental monitors of the cosmic ray flux. This correlation is exploited to extrapolate test-mass charging rates to a 20-year period giving useful insight into the expected range of charging rate that may be observed in the LISA mission.

Abstract

A comprehensive summary of the measurements made to characterize test-mass charging due to the space environment during the LISA Pathfinder mission is presented. Measurements of the residual charge of the test mass after release by the grabbing and positioning mechanism show that the initial charge of the test masses was negative after all releases, leaving the test mass with a potential in the range from −12 to −512. Variations in the neutral test-mass charging rate between 21.7 and 30.7  e s$^{−1}$ were observed over the course of the 17-month science operations produced by cosmic ray flux changes including a Forbush decrease associated with a small solar energetic particle event. A dependence of the cosmic ray charging rate on the test-mass potential between −30.2 and −40.3  e s$^{−1}$ V$^{−1}$ was observed resulting in an equilibrium test-mass potential between 670 and 960 mV, and this is attributed to a contribution to charging from low-energy electrons emitted from the gold surfaces of the gravitational reference sensor. Data from the onboard particle detector show a reliable correlation with the charging rate and with other environmental monitors of the cosmic ray flux. This correlation is exploited to extrapolate test-mass charging rates to a 20-year period giving useful insight into the expected range of charging rate that may be observed in the LISA mission.

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Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Scopus Subject Areas:Physical Sciences > Nuclear and High Energy Physics
Language:English
Date:22 March 2023
Deposited On:01 Jan 2024 14:51
Last Modified:28 Jun 2024 03:32
Publisher:American Physical Society
ISSN:2470-0010
OA Status:Hybrid
Publisher DOI:https://doi.org/10.1103/physrevd.107.062007
Project Information:
  • : FunderCentre National de la Recherche Scientifique
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  • : FunderUniversité Paris Diderot
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  • : FunderDeutsches Zentrum für Luft- und Raumfahrt
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  • : FunderInstituto Nazionale di Fisica Nucleare
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  • : FunderConsejo Superior de Investigaciones Científicas
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  • : FunderUK Space Agency
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  • : FunderSchweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
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  • : FunderUniversity of Glasgow
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  • : FunderUniversity of Birmingham
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  • : FunderImperial College London
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  • : FunderScottish Universities Physics Alliance
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  • : FunderNational Aeronautics and Space Administration
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  • : FunderSwiss Space Office
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  • Content: Published Version
  • Language: English
  • Licence: Creative Commons: Attribution 4.0 International (CC BY 4.0)