Articles | Volume 23, issue 8
Ann. Geophys., 23, 2813–2823, 2005

Special issue: Double Star - First Results

Ann. Geophys., 23, 2813–2823, 2005

  08 Nov 2005

08 Nov 2005

Spacecraft potential control for Double Star

K. Torkar1, H. Arends2, W. Baumjohann1, C. P. Escoubet2, A. Fazakerley3, M. Fehringer2, G. Fremuth1, H. Jeszenszky1, G. Laky1, B. T. Narheim4, W. Riedler1, F. Rüdenauer5, W. Steiger5, K. Svenes4, and H. Zhao6 K. Torkar et al.
  • 1Space Research Institute, Austrian Academy of Sciences, A-8042 Graz, Austria
  • 2ESA/ESTEC, NL-2200 AG Noordwijk, The Netherlands
  • 3Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, UK
  • 4Norwegian Defence Research Establishment (FFI), N-2007 Kjeller, Norway
  • 5Austrian Research Centers Seibersdorf, A-2444 Seibersdorf, Austria
  • 6Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100080, P. R. China

Abstract. The spacecraft potential of Double Star TC-1 is positive in large parts of the orbits due to the photo-effect from solar EUV irradiation. These positive potentials typically disturb low energy plasma measurements on board. The potential can be reduced, and thereby the particle measurements improved, by emitting a positive ion beam. This method has successfully been applied on several other spacecraft and it has also been chosen for TC-1. The instrument TC-1/ASPOC is a derivative of the Cluster/ASPOC instruments, from which it has inherited many features. The paper describes the adaptations and further developments made for the ion emitters and the electronics. The instrument performs very well and can support higher beam currents than on Cluster. The expected significant improvement of the low energy particle measurements on board was indeed observed. The modifications of the electron distributions are analysed for a one-time interval when the spacecraft was located in the magnetosheath. The change in the potential due to the ion beam was determined, and first studies of the 3-D electron distributions in response to the spacecraft potential control have been performed, which indicate that the method works as expected.