|Instrument: LEP : Low Energy Particles (Geotail)|
Solar/Space Observing Instruments
Instrument Class: Particle Detectors
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The objective of the LEP experiment on Geotail is to observe plasma and
energetic electrons and ions in the terrestrial magnetosphere and in the
The LEP consists of three sensors: LEP-EA, LEP-SW, and LEP-MS, with common
LEP-EA measures three-dimensional velocity distributions of hot plasma in the
magnetosphere. EA consists of two nested sets of quadrispherical electrostatic
analyzers. The inner analyzer measures electrons in the energy range from 6--36
eV, and the outer one measures positive ions from 7 eV/Q to 42 keV/Q. The field
of view for each quadrispherical analyzer covers 10 degrees by 145 degrees,
where the longer dimension is parallel to the satellite spin axis.
LEP-SW measures three-dimensional velocity distributions of solar wind ions in
the energy range from 0.1--8 keV/Q with a 270 degree spherical electrostatic
analyzer with a field of view of 5 degrees by 60 degrees.
LEP-MS is an energetic ion mass spectrometer, which provides three-dimensional
determinations of the ion composition in 32 steps over the energy range of
0--25 keV/Q. All sensors operate continuously as long as the spacecraft power
budget can allow, except for the orbit/attitude maneuvering operation.
When spacecraft power budget is not sufficient to fully operate the
instruments, priority is given to LEP-EA and LEP-E.
Although this experiment ceased operation shortly after launch, the LEP-EA and
LEP-SW portions of the experiment resumed operation in late 1993 and have
worked well ever since.
Dr. Tsugunobu Nagai
Tokyo Institue of Technology
Earth and Planetary Sciences
Tokyo 152-8551 Japan
Instrument Start Date: 1992-07-24
Instrument Owner: ISAS, Japan