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Instrument Descriptions



CPI The objective of this investigation is to make comprehensive observations of the three-dimensional velocity distribution functions of electrons and positive ions, with identification of ion species. The instrument contains three sets of quadrispherical analyzers with channel electron multipliers. These three obtain three-dimensional measurements for hot plasma and solar wind electrons, for solar wind ions, and for positive-ion composition measurements. The positive-ion composition measurement includes five miniature imaging mass spectrometers at the exit aperture of the analyzer, and covers masses from 1 to 550 u/Q at 100 eV, and 1 to 55 u/Q at 10 keV. The hot plasma analyzer measures electrons and ions in the range 1-50,000 eV/Q. The solar wind analyzer measures ions from 150 to 7,000 eV/Q. Sequencing of the energy analyzers and mass spectrometers, and other control functions, are provided by two microprocessors.

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Principle Investigator:

    Prof. Louis A. Frank
    Department of Physics and Astonomy
    The University of Iowa
    Van Allen Hall, Iowa cty, IA 52242-1479
    Phone:  1-319-335-1695
    Fax:    1-319-335-1753
    e-mail: frank@iowasp.physics.uiowa.edu
    

EFD The objectives of this investigation are studies of (1) the large scale configuration of the electric field in the magnetotail, (2) tail electric field variations during substorms, (3) the electric field in the plasma sheet, (4) the electric field near the magnetopause and in the plasma mantle at locations tailward of those covered by similar measurements on ISEE 1, (5) micropulsation and low frequency wave measurements at frequencies covering the local gyrofrequency (<1Hz) and lower hybrid frequency (<10Hz) in the tail, (6) plasma density as deduced from measurement of the floating potential of the spacecraft, and (7) electric field comparisons (with the aid of the other spacecraft in the ISTP program) at different points along the same magnetic field line, at different points along a common boundary, or in different regions of the magnetosphere.

The instrument consists of two orthogonal double probes, each of which is a pair of separated spheres on wire booms that are located in the satellite spin plane and whose difference of potential is measured. The separation distances between the pair of sensors are variable and as great as 160 m tip-to-tip. One operating mode involves length ratios of the two antennas of about 2:1 in order to verify instrument operation through showing that the electric field signature is proportional to the boom length. A second reason for two pairs of wire booms in the satellite spin plane is the requirement for measurements having a time resolution far better than the satellite spin period.

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Principle Investigator:

    Dr. Koichiro Tsuruda
    The Institute of Space and Astronautical Science
    3-1-1 Yoshinodai, Sagamihara
    Kannagawa 229, Japan
    Phone:  81-427-51-3911 ext. 2501
    Fax:    81-427-59-4236
    e-mail: tsuruda@fujitubo.gtl.isas.ac.jp
    

EPIC The principal objective of the EPIC (Energetic Particle and Ion Composition) investigation is to explore the distant magnetotail region and obtain information on the origin, transport, storage, acceleration and dynamics of suprathermal and non-thermal particle populations.

The instrument performs three-dimensional distribution measurements by using both total energy, E/Q and time of flight (STICS -- Supra-Thermal Ion Composition Spectrometer) and Velocity/Energy (ICS -- Ion Composition Subsystem) detectors. These measure Ions >8 keV/charge and Ions/Electrons >35 keV, respectively.

Composition measurements are made by using a thin foil time-of-flight technique which resolves the H and He isotopes, and provides elemental resolution up to approximately argon. The instrument also measures the non-thermal components to 6 MeV for protons, 480 keV for electrons, and 400 keV/nucleon for ions with Z>2. Directional measurements with a time resolution <3 s are possible.

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Principle Investigator:

    Richard McEntire
    Applied Physics Lab, Johns Hopkins University
    John Hopkins Road
    Laurel, MD 20723-6099
    Phone: 240-228-5410 
    Fax:    
    e-mail: Dick.McEntire@jhuap1.edu
    

HEP There are three scientific objectives to be studied by this investigation: (1) plasma dynamics in the geomagnetic tail, (2) solar flare particle acceleration and propagation, and (3) the origin, lifetime and propagation of cosmic ray particles. There are five instruments that make up this investigation: Low-energy particle Detector (LD), Burst Detector (BD), Medium-energy Isotope detectors (MI-1 and MI-2), and High energy Isotope detector (HI).

LD and BD are mainly dedicated to magnetospheric studies.

MI and HI concentrate on solar flare and cosmic ray studies.

The LD sensor system consists of three identical Imaging Ion Mass spectrometers which use time-of-flight/energy measurement, and covers 180 degrees in polar angle over the energy range 20--300 keV for electrons, 2 keV--1.5 MeV for protons, and 2 keV--1.5 MeV per charge for ions. LD provides distribution of electrons and ions with complete coverage of the unit sphere in phase space, and electron and proton flux in 4 azimuth sectors, helium and oxygen flux at an azimuth of 0 degrees.

The BD sensor consists of three delta-E x E telescopes which identify particles by their energy loss and residual energy over the energy range 0.12--2.5 MeV for electrons, 0.7--35 MeV for protons, and 0.7--140 MeV for helium. The three telescopes each have an opening angle of 30 degrees by 45 degrees with look directions of 30, 90, and 150 degrees to the spin axis. BD provides count rates for high energy electrons, protons and helium, as well as electron and proton fluxes in four 90 degree azimuth bins.

The MI and HI instruments are all silicon semiconductor detector telescopes utilizing the well-known dE/dx x E algorithm for isotope identification: mass and nuclear charge. The MI instrument measures elemental and isotopic compositions of solar energetic particles and energetic particles in the heliosphere with 2<Z<28 in the 2.4--80 MeV/nucleon energy range , and measures the elemental composition of solar energetic particles heavier than iron. The HI instrument also measures elemental and isotopic compositions of solar energetic particles and galactic cosmic rays with 2<Z<28 in the 10-210 MeV/nucleon energy range.

HEP operates continuously with no change in allocated bit rate. LD has two operational modes: normal and burst. Burst mode is an internal high speed mode which does not change the data output.

BD has four operational modes for calculating energy spectra for electrons, protons, and helium: 16 sectors in 1 spin (time high resolution mode), 8 sectors in 32 spins (energy high resolution mode), 8 sectors in 2 spins, and 16 sectors in 4 spins. MI and HI have only one operational mode.

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LEP The objective of this experiment is to observe plasma and energetic electrons and ions in the terrestrial magnetosphere and in the interplanetary medium.

The LEP consists of three sensors: LEP-EA, LEP-SW, and LEP-MS, with common electronics (LEP-E).

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.

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Principle Investigator:

    Prof. Toshifumi Mukai
    The Institute of Space and Astronautical Science
    3-1-1, Yoshinodai, Sagamihara
    Kanagawa 229, Japan
    Phone:  81-427-51-3911
    Fax:    81-427-59-4236
    e-mail: mukai@fujitubo.gtl.isas.ac.jp
    

MGF The objective of this experiment is to measure the magnetic field variation of the magnetotail in the frequency below 50 Hz.

The MGF experiment consists of dual three-axis fluxgate magnetometers and a three-axis search coil magnetometer. Triad fluxgate sensors, which utilize a ring core geometry, are installed at the end and middle of a 6 m deployable mast. Three search coils are mounted approximately one-half of the way out on another 6 m boom together with search coils for the VLF wave in the PWI system.

The fluxgate magnetometers are of standard design and consist of an amplifier, filter, phase sensitive detector, integrator, and a voltage-current convertor. The fluxgate magnetometers operate in seven dynamic ranges to cover various regions of the Earth's magnetosphere and the solar wind: +/-16 nT, +/-64 nT, +/-256 nT, +/-1024 nT, +/-4096 nT, +/-16384 nT, and +/-65536 nT, and supply 16 vectors/sec.

The search coil magnetometer system consists of three sensors, preamplifier, amplifier, filter, multiplexer, and an A/D converter. The search coil magnetometers operate in a frequency range of 0.5 kHz to 1 kHz, and supply 128 vectors/sec.

The fluxgate magnetometer operates in both real time and record modes, while the search coil data are used only in real time mode.

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Principle Investigator:

    Dr. Tsugunobu Nagai 
    Tokyo Institue of Technology
    Earth and Planetary Sciences
    Tokyo 152-8551  Japan
    Phone:  
    Fax:   
    e-mail: nagai@geo.titech.ac.jp
    

PWI The objective of this investigation is to determine the dynamic behavior of the plasma trapped in the earth's magnetosphere (i.e. toroidal and poloidal currents, oscillations and waves in the plasmas, ion entrance and exit via the ionosphere and solar wind, and the extent of the plasma sheath).

The instrument measures electric fields over the range 0.5 Hz to 400 kHz, and magnetic fields over the range 1 Hz to 10 kHz. Triaxial magnetic search coils are utilized in addition to a pair of electric dipole antennas. The instrument contains two sweep-frequency receivers (12 Hz to 400 kHz and 12 Hz to 6.25 kHz), a multichannel analyzer (5.6 Hz to 311 kHz for the electric antenna and 5.6 Hz to 1.0 kHz for the magnetic coils), a low frequency waveform receiver (0.01 to 10 Hz), and a wideband waveform receiver (10 Hz to 16 kHz).

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Principle Investigator:

    Prof. Hiroshi Matsumoto
    Radio Atmospheric Science Center
    Kyoto University
    Gokasho, Uji, Kyoto 611, Japan
    Phone:  81-774-33-2532
    Fax:    81-774-31-8463
    e-mail: matsumoto@kurasc.kyoto-u.ac.jp
    

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