The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed the Van Allen Probes) are designed to measure three dimensional quasi-static and low frequency electric fields and waves associated with the major mechanisms responsible for the acceleration of energetic charged particles in the inner magnetosphere of the Earth. For this measurement, the instrument uses two pairs of spherical double probe sensors at the ends of orthogonal centripetally deployed booms in the spin plane with tip-to-tip separations of 100 meters. The third component of the electric field is measured by two spherical sensors separated by ∼15 m, deployed at the ends of two stacer booms oppositely directed along the spin axis of the spacecraft. The instrument provides a continuous stream of measurements over the entire orbit of the low frequency electric field vector at 32 samples/s in a survey mode. This survey mode also includes measurements of spacecraft potential to provide information on thermal electron plasma variations and structure. Survey mode spectral information allows the continuous evaluation of the peak value and spectral power in electric, magnetic and density fluctuations from several Hz to 6.5 kHz. On-board cross-spectral data allows the calculation of field-aligned wave Poynting flux along the magnetic field. For higher frequency waveform information, two different programmable burst memories are used with nominal sampling rates of 512 samples/s and 16 k samples/s. The EFW burst modes provide targeted measurements over brief time intervals of 3-d electric fields, 3-d wave magnetic fields (from the EMFISIS magnetic search coil sensors), and spacecraft potential. In the burst modes all six sensor-spacecraft potential measurements are telemetered enabling interferometric timing of small-scale plasma structures. In the first burst mode, the instrument stores all or a substantial fraction of the high frequency measurements in a 32 gigabyte burst memory. The sub-intervals to be downloaded are uplinked by ground command after inspection of instrument survey data and other information available on the ground. The second burst mode involves autonomous storing and playback of data controlled by flight software algorithms, which assess the "highest quality" events on the basis of instrument measurements and information from other instruments available on orbit. The EFW instrument provides 3-d wave electric field signals with a frequency response up to 400 kHz to the EMFISIS instrument for analysis and telemetry (Kletzing, et al. Space Sci. Rev. 2013).
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Acknowledgements We would like to acknowledge the many contributions of the RBSP Project team at Johns Hopkins Applied Physics Laboratory. We would like to also thank the EFW team of scientists and engineers at Space Science Laboratory at the University of California, Berkeley and the staff at the Laboratory for Atmospheric and Space Physics at the University of Colorado in the development and test of the instrument. We also thank the efforts of the other instrument teams on the RBSP mission. We would like to acknowledge the contributions of the EMFISIS team, the ECT team (MagEIS, HOPE and REPT), and the RBSPICE team. In this paper, the energetic electron figures were provided by Joe Fennell, J.B. Blake, and Harlan Spence of the MagEIS/ECT teams. This work was supported by RBSP-ECT funding provided by JHU/APL Contract No. 967399 under NASA’s Prime Contract No. NAS5-01072. The work by the EFW team was conducted under JHU/APL contract 922613 (RBSP-EFW).
- Electric fields