Geoscience Reference
In-Depth Information
waves up to 10 MHz for electric field and up to 640 kHz for magnetic field.
SORBET is connected to the WPT, MEFISTO, and DB-SC sensors.
The AM
2
P measures the antenna impedance of the MEFISTO elec-
tric field sensors. It feeds a series of current pulses onto the electric field
sensors and monitors the voltage response. The obtained data sets pro-
vide us with information on the antenna impedance, which is used for
precise calibration of the observed electric field data. Since the antenna
impedance strongly depends on plasma parameters, the data sets of AM
2
P
are also useful for measuring
in situ
plasma densities and temperatures.
The function of measuring the WPT antenna impedance is provided by a
part of EWO.
The PWI electronics board will be installed into the MDP-2 (Mission
Data Processor) chassis developed by ISAS/JAXA, as the MMO system
team. Data processing unit (DPU) in the MDP-2 will manage the data
processing and command control for PWI and will employ event detection
algorithm to find expected or unknown events and will distribute triggering
signal among other experiments.
MDP-2 will also be in charge of controlling the data flows and the oper-
ation of the MGF-I (magnetic field-inboard), MSASI (sodium exosphere
imager) and MDM (dust monitor).
4. Expected Performance
4.1.
Electric field detection: from DC to 10MHz
WPT and MEFISTO each measure orthogonal components of the elec-
tric field in the spacecraft spin plane using complementary sensor designs.
WPT offers superior sensitivity at high frequencies whereas MEFISTO
offers superior sensitivity at low frequencies. For all intermediate frequen-
cies both sensors offer excellent sensitivity and the electric field vector in
the spin plane can be reconstructed. Weak radio waves will mainly be reg-
istered by WPT whereas weak low-frequency fluctuations will mainly be
detected by MEFISTO. For DC electric fields, both sensors provide su-
cient sensitivity for all scientific objectives.
For DC electric fields (sampled by EWO), the PWI will cover the
dynamic range and resolution of the DC electric field expected in Mercury's
magnetosphere and in the solar wind, less than 500 mV/m with resolution
of 0.015 mV/m. The sensitivities for AC electric field measurements (by
EWO and SORBET) are summarized in Fig. 4.
