The Electric Field Instrument (EFI) for THEMIS
The design, performance, and on-orbit operation of the three-axis electric field instrument (EFI) for the NASA THEMIS mission is described. The 20 radial wire boom and 10 axial stacer boom antenna systems making up the EFI sensors on the five THEMIS spacecraft, along with their supporting electronics have been deployed and are operating successfully on-orbit without any mechanical or electrical failures since early 2007. The EFI provides for waveform and spectral three-axis measurements of the ambient electric field from DC up to 8 kHz, with a single, integral broadband channel extending up to 400 kHz. Individual sensor potentials are also measured, providing for on-board and ground-based estimation of spacecraft floating potential and high-resolution plasma density measurements. Individual antenna baselines are 50- and 40-m in the spin plane, and 6.9-m along the spin axis.
The EFI has provided for critical observations supporting a clear and definitive understanding of the electrodynamics of both the boundaries of the terrestrial magnetosphere, as well as internal processes, such as relativistic particle acceleration and substorm dynamics. Such multi-point electric field observations are key for pushing forward the understanding of electrodynamics in space, in that without high-quality estimates of the electric field, the underlying electromagnetic processes involved in current sheets, reconnection, and wave-particle interactions may only be inferred, rather than measured, quantified, and used to discriminate between competing hypotheses regarding those processes.
KeywordsElectric field instrumentation Electrodynamics Reconnection Substorms
Unable to display preview. Download preview PDF.
- C. Cattell, J.R. Wygant, K. Goetz, K. Kersten, P.J. Kellogg, T. von Rosenvinge, S.D. Bale, I. Roth, M. Temerin, M.K. Hudson, R.A. Mewaldt, M. Wiedenbeck, M. Maksimovic, R. Ergun, M. Acuna, C.T. Russell, Discovery of very large amplitude whistler-mode waves in Earth’s radiation belts. Geophys. Res. Lett. 35, L01105 (2008). doi:10.1029/2007GL032009 CrossRefGoogle Scholar
- C.M. Cully, R.E. Ergun, A.I. Eriksson, Electrostatic structure around spacecraft in tenuous plasmas, J. Geophys. Res. (2006) Google Scholar
- Cully et al., THEMIS DFB, Space Sci. Rev. (2008a, this issue) Google Scholar
- E. Engwald, Numerical studies of spacecraft-plasma interaction: simulation of wake effects on the Cluster electric field instrument EFW. IRF Scientific Report 284, Feb 2004 Google Scholar
- M. Ludlam et al., THEMIS magnetic cleanliness specification. Space Sci. Rev. (2008, this issue) Google Scholar
- J.P. McFadden, C.W. Carlson, D. Larson, J. Bonnell, F.S. Mozer, V. Angelopoulos, K.-H. Glassmeier, U. Auster, Structure of plasmaspheric plumes and their participation in magnetopause reconnection: first results from THEMIS. Geophys. Res. Lett. 35, L17S10 (2008a). doi:10.1029/2008GL033677 CrossRefGoogle Scholar
- J.P. McFadden, C.W. Carlson, D. Larson, V. Angelopoulos, M. Ludlam, R. Abiad, B. Elliot, P. Turin, M. Marckwordt, The THEMIS ESA plasma instrument and in-flight calibration. Space Sci. Rev. (2008b, in press) Google Scholar
- F.S. Mozer, J.-J. Berthelier, U.V. Fahleson, C.-G. Fälthammar, A proposal to measure the quasi-static vector electric field on the low altitude and the elliptic orbiting electrodynamics explorer satellites. Research Proposal to the National Aeronautics and Space Administration, UCBSSL No. 552/75, 1974 Google Scholar
- A. Pedersen, F. Mozer, G. Gustafsson, Electric field measurements in a tenuous plasma w0ith spherical double probes, in Measurement Techniques in Space Plasmas: Fields. Geophysical. Monograph, vol. 103 (AGU, 1998) Google Scholar
- K. Sahu, S. Kniffen, Technical memo, PPM-98-008, Radiation report on OP15 (Analog Devices) (LDC9722A), Unisys Corporation—Federal Systems Division, 23 April 1998 Google Scholar