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- The Electric Field Instrument (EFI) on the Polar spacecraft measures the three
components of the ambient vector electric field and the thermal electron
density.
The electric field and plasma density measurements are made over a frequency
range of DC to above 20 kHz. The dynamic range of the electric field
measurement is 0.02 to 1000 mV/m, while the plasma density will be measured at
least over the range of 0.1 to 100 particles per cubic centimeter. A by-product
of the experiment is measurement of the floating potential of the spacecraft
over the range of about +1 to +90 volts.
An important component of the Electric Field Instrument is a two megabyte burst
memory that allows storage of high time resolution field and plasma density
measurements, allowing study of rapid variations of non-linear spatial
structures and waves.
The EFI sensors are arranged as three orthogonal sphere pairs whose potential
differences and Langmuir probe characteristics are measured. Two of these
sphere pairs are in the satellite spin plane on the ends of wire booms that
provide tip to tip sphere separations of 100 and 130 meters respectively, while
the third pair is aligned along the spacecraft spin axis with a 14 meter tip to
tip separation that is provided by rigid stacer booms.
The electric field preamplifiers have frequency responses to above one mHz to
accommodate their use by the Plasma Wave Instrument. In addition, the Electric
Field Instrument interfaces on the spacecraft with the Magnetic Field
Expirement (which provides information for deciding when to trigger bursts of
data collection), the Hydra plasma experiment (in order that both instruments
collect high time resolution data simultaneously), and the low energy plasma
experiment, Tide, (which wants to know when the Electric Field Instrument is
collecting data in the burst mode).
The heritage for the Electric Field Instrument encompasses instruments
previously flown on the S3-3, GEOS, ISEE-1, Viking, and CRRES satellites, as
well as experiments being built for the Freja, FAST, and Cluster satellites.
Harvey, P., F. S. Mozer, D. Pankow, J. Wygant, N. C. Maynard, H. Singer, W.
Sullivan, P. B. Anderson, R. Pfaff, T. Aggson, A. Pedersen, C. G. Falthammar,
and P. Tanskannen, THE ELECTRIC FIELD INSTRUMENT ON THE POLAR SATELLITE, Space
Science Reviews 71: 583-596, 1995.
http://ssed.gsfc.nasa.gov/PolarEFI/Instrument/instrument.html
For more information, see:
http://ssed.gsfc.nasa.gov/PolarEFI/
and
http://pwg.gsfc.nasa.gov/polar/polar_inst.shtml
Group: Instrument_Details
Entry_ID: EFI
Group: Instrument_Identification
Instrument_Category: Solar/Space Observing Instruments
Instrument_Class: Magnetic Field/Electric Field Instruments
Short_Name: EFI
Long_Name: Electric Fields Investigation
End_Group
Group: Associated_Platforms
Short_Name: POLAR
End_Group
Online_Resource: http://ssed.gsfc.nasa.gov/PolarEFI/index.html
Online_Resource: http://ssed.gsfc.nasa.gov/PolarEFI/Instrument/instrument.html
Group: Instrument_Logistics
Instrument_Start_Date: 1996-02-24
Instrument_Owner: NASA
End_Group
End_Group
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