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MMS 4 Active Spacecraft Potential Control (ASPOC), Sensors 1 and 2, Level 2 (L2), Survey Mode, 1 s Data

Published by MMS_SDC, CDAWeb | National Aeronautics and Space Administration | Catalog Last Checked: September 01, 2026 at 11:41 PM | Dataset Last Updated: September 01, 2026
MMS 4 Active Spacecraft Potential Control (ASPOC) - Sensors 1 and 2 Ion Beam Current Rates, Beam Energies, and Instrument Status variables. In tenuous plasma regions, the floating potential of a sunlit spacecraft is positively charged, reaching up to tens of Volts. The corresponding electric field disturbs the ambient plasma measurements obtained from electron and ion sensors and the large fluxes of attracted photo-electrons can significantly reduce the lifetime of the micro-channel plate. The electric field measurements can be also contaminated by the high spacecraft potential values. The Active Spacecraft Potential Control neutralizes the spacecraft potential by releasing positively charged Indium ions. The ASPOCs neutralize the electrical potential of the spacecraft, limiting or eliminating spurious electric fields that can contaminate measurements. This allows observations of the more scientifically important low-energy ions and electrons.

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Complete Metadata
@type dcat:Dataset
accessLevel public
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[
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]
contactPoint 
{
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}
description MMS 4 Active Spacecraft Potential Control (ASPOC) - Sensors 1 and 2 Ion Beam Current Rates, Beam Energies, and Instrument Status variables. In tenuous plasma regions, the floating potential of a sunlit spacecraft is positively charged, reaching up to tens of Volts. The corresponding electric field disturbs the ambient plasma measurements obtained from electron and ion sensors and the large fluxes of attracted photo-electrons can significantly reduce the lifetime of the micro-channel plate. The electric field measurements can be also contaminated by the high spacecraft potential values. The Active Spacecraft Potential Control neutralizes the spacecraft potential by releasing positively charged Indium ions. The ASPOCs neutralize the electrical potential of the spacecraft, limiting or eliminating spurious electric fields that can contaminate measurements. This allows observations of the more scientifically important low-energy ions and electrons.
distribution 
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identifier https://doi.org/10.48322/3470-wp93
keyword 
[
  "instrumentstatus"
]
landingPage https://doi.org/10.48322/3470-wp93
license https://www.usa.gov/government-works
modified 2026-09-01
programCode 
[
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publisher 
{
  "name": "MMS_SDC, CDAWeb",
  "@type": "org:Organization"
}
theme 
[
  "Heliophysics"
]
title MMS 4 Active Spacecraft Potential Control (ASPOC), Sensors 1 and 2, Level 2 (L2), Survey Mode, 1 s Data

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