Active Spacecraft Potential Control in the MMS Mission: Results from Six Years in Orbit

K. Torkar*, R. Nakamura, O. W. Roberts, H. Jeszenszky, P. A. Lindqvist, Y. Khotyaintsev, B. L. Giles, A. C. Barrie

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The four spacecraft of the NASA Magnetospheric Multiscale (MMS) mission carry instruments to reduce the positive potential by means of indium ion beams. Since the start of the nominal mission in September 2015 and until the end of 2021, the instruments active spacecraft potential control (ASPOC) have been actively operating for more than 16 000 h at a nominal emission current of $20 \mu \text{A}$ per spacecraft. Based on data from more than six years in orbit with more than 50 000 h in regions of scientific interest, statistical results regarding the potential's interdependencies with ambient plasma were obtained. This article reports on the derivation of the photo electron energy spectrum from the correlation between the potential and the plasma data obtained by the fast plasma instrument with and without controlled potential. Finally, the time constants during the relaxation of the controlled potential when the active control instrument is turned off, if measured at high time resolution, allow to estimate the electric capacitance of the spacecraft system.

Original languageEnglish
Pages (from-to)2461-2467
Number of pages7
JournalIEEE Transactions on Plasma Science
Issue number9
Early online date08 May 2023
Publication statusPublished - 01 Sept 2023
Externally publishedYes


  • Electrostatic potentials
  • ion emission
  • magnetosphere
  • plasma measurements
  • solar wind
  • space vehicles
  • surface charging


Dive into the research topics of 'Active Spacecraft Potential Control in the MMS Mission: Results from Six Years in Orbit'. Together they form a unique fingerprint.

Cite this