THEMIS Electric Field Instrument EFI J W Bonnell

THEMIS Electric Field Instrument (EFI) J. W. Bonnell Space Sciences Laboratory Univ. of Calif. , Berkeley THEMIS SRR 1 UCB, June 8 -9, 2003

EFI Block Diagram A High-Input Impedance, Low-Noise Voltmeter in Space sheath sensor preamp floating ground generation bias generation THEMIS SRR 2 UCB, June 8 -9, 2003

Science Requirements • • EFI-1: The EFI shall determine the 2 D 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 1830 Re (4. 1. 1. 3). The EFI shall measure the 3 D 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). THEMIS SRR 3 UCB, June 8 -9, 2003

Performance Requirements • • • EFI-5: The EFI shall measure the 2 D spin plane DC E-field with a time resolution of 10 s (EFI-1, EFI-2). EFI-6: The EFI shall measure the 3 D AC E-field from 1 Hz to 4 k. Hz (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 k. Hz, with df/f~25% (EFI-3). EFI-9: The EFI shall measure DC-coupled signals of amplitude up to 300 m. V/m with 16 -bit resolution. EFI-10: The EFI shall measure AC-coupled signals of amplitude up to 100 m. V/m with 16 -bit resolution. EFI-11: The EFI noise level shall be below 10 -4 (m. V/m)/Hz 1/2 [TBR]. EFI-12: The EFI HF RMS (log power) measurement shall cover 100 -500 k. Hz 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 m. V/m in the SC XY E-field components during times of onset (EFI-1, EFI-2). THEMIS SRR 4 UCB, June 8 -9, 2003

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 m. V resolution, better than 46 u. V/m resolution (allows ground reconstruction of E from spacecraft potential to better than 0. 1 m. V/m resolution). DC-coupled E-field: +/- 300 m. V/m, 9 u. V/m resolution. AC-coupled E-field: <= +/- 100 m. V/m, 3 u. V/m resolution. THEMIS SRR 5 UCB, June 8 -9, 2003