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Double-probe spaceborne electric field sensor (DSEFS) was used to detect the ionospheric electric field abnormal of
earthquake precursor. The DSEFS is comprised of four probes and four booms outside the satellite and one signal
acquisition and processing system inside the satellite. Four cylindric electrodes called C2 of the probes were used to
connect the booms and the probes. The length of C2 is one of the most important geometric parameter need to be
optimized to ensure the detecting precision of DSEFS. In order to understand the operation of the electric field probes
and optimize its performance, Spacecraft Plasma Interaction System (SPIS) software and DEMETER detected data were
used to study the influence of C2 length on the DSEFS detection precision. The simulation results showed that when the
C2 length is bigger than 2 Debye lengths, the influence of the boom potential had almost no disturbance on the DSEFS
probes. In the case of short C2 length, when the boom had a potential which is positive with respect to the probes, the
local electric field between the boom and the probe was the dominant factor, the probe collected currents monotonously
increased with the increasing of C2 length. When the boom has a negative potential with respect to the probe, the probe
collected current did not monotonously increased with the increasing of C2 length, when the length of C2 is relatively
short (less than 20cm), the effect of boom sheath was the dominant factor, the probe collected current increased with the
increasing of C2 length; when the length of C2 is larger than 20cm, the local electric field became the dominant factor,
the probed colleted current decreased with the increasing of C2 length. The computer simulation result provided good
guidance on optimization design of the C2 length of DSEFS.
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