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THEMIS Electric Field Instrument (EFI) J. W. Bonnell Space Sciences Laboratory

THEMIS Electric Field Instrument (EFI) J. W. Bonnell Space Sciences Laboratory Univ. of Calif., Berkeley. EFI Block Diagram. A High-Input Impedance, Low-Noise Voltmeter in Space. sheath. sensor. preamp. floating ground generation. bias generation. Science Requirements.

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THEMIS Electric Field Instrument (EFI) J. W. Bonnell Space Sciences Laboratory

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  1. THEMIS Electric Field Instrument (EFI) • J. W. Bonnell • Space Sciences Laboratory • Univ. of Calif., Berkeley

  2. EFI Block Diagram A High-Input Impedance, Low-Noise Voltmeter in Space sheath sensor preamp floating ground generation bias generation

  3. Science Requirements • EFI-1: The EFI shall determine the 2D spin plane electric field at the times of onset at 8-10 Re (4.1.1.7, 4.1.1.9). • EFI-2: The EFI shall determine the dawn-dusk electric field at 18-30 Re (4.1.1.3). • The EFI shall measure the 3D wave electric field from 1-600 Hz at the times of onset at 8-10 Re (4.1.1.11). • The EFI shall measure the waves at frequencies up to the electron cyclotron frequency that may be responsible for electron acceleration in the radiation belt (radiation belt science).

  4. Performance Requirements • EFI-5: The EFI shall measure the 2D spin plane DC E-field with a time resolution of 10 s (EFI-1, EFI-2). • EFI-6: The EFI shall measure the 3D AC E-field from 1 Hz to 4 kHz (EFI-3). • EFI-7: The EFI shall measure the Spacecraft Potential with a time resolution better than the spin rate (3 s; from ESA to compute moments). • EFI-8: The EFI FFT Spectra range shall be 16 Hz to 4 kHz, with df/f~25% (EFI-3). • EFI-9: The EFI shall measure DC-coupled signals of amplitude up to 300 mV/m with 16-bit resolution. • EFI-10: The EFI shall measure AC-coupled signals of amplitude up to 100 mV/m with 16-bit resolution. • EFI-11: The EFI noise level shall be below 10-4 (mV/m)/Hz1/2 [TBR]. • EFI-12: The EFI HF RMS (log power) measurement shall cover 100-500 kHz with a minimum time resolution of the spin rate (on-board triggers). • EFI-13: The EFI shall achieve an accuracy better than 10% or 1 mV/m in the SC XY E-field components during times of onset (EFI-1, EFI-2).

  5. Performance Specification • EFI radial sensor baseline will be 40 m, tip-to-tip. • EFI axial sensor baseline will be ~10 m, tip-to-tip. • 16-bit resolution. • Spacecraft potential: +/- 60 V, 1.8 mV resolution, better than 46 uV/m resolution (allows ground reconstruction of E from spacecraft potential to better than 0.1 mV/m resolution). • DC-coupled E-field: +/- 300 mV/m, 9 uV/m resolution. • AC-coupled E-field: <= +/- 100 mV/m, 3 uV/m resolution.

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