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Instrument Descriptions


WAVES

Experiment Overview

    The Sun and the Earth emit radio waves that affect particles in the interplanetary plasma and carry some of the energy flowing there. The Radio and Plasma Wave experiment will measure the properties of these waves and other wave modes of the plasma over a wide frequency range. Analyses of these measurements, in coordination with the other onboard plasma, energetic particles, and field measurements, will further the understanding of solar wind and interplanetary plasma processes.

Science Objectives

    To provide comprehensive measurements of the radio and plasma wave phenomena which occur in the solar wind upstream of the Earth's magnetosphere and in key regions of the magnetosphere.

Measurement Objectives

    To obtain the following measurements:
    • Low-frequency electric waves and low-frequency magnetic fields, from DC to 10 kHz.
    • Electron thermal noise, from 4 kHz to 256 kHz.
    • Radio waves, from 20 kHz to 14 MHz.
    • Time domain waveform sampling, to capture short duration events which meet quality criteria set into the WAVES data processing unit (DPU).
Description of Instrument
    The sensor system of the WAVES experiment consists of three electric antenna systems (two coplanar, orthogonal wire antennas in the spin-plane and a rigid spin-axis dipole) and a triaxial magnetic search coil. The longer and shorter spin plane dipoles have lengths of 50 m and 7.5 m for each wire, respectively, while each spin-axis dipole extends 5.28 m from the top and bottom surfaces of the spacecraft. The triaxial magnetic search coil for measuring bi-frequency magnetic fields is mounted at the outboard end of a 12-m radial boom.

    There are five main receiver systems: a bi-frequency (DC to 10 kHz) Fast Fourier Transform receiver, a broadband (4 kHz to 256 kHz) electron thermal noise receiver, two swept-frequency radio receivers (20 kHz to lMHz, and lMHz to 14 MHz), and a time domain waveform sampler (up to 120,000 samples per second). The DPU controls and acquires data from all operations of the experiment, and can be reprogrammed from the ground. The receiver systems and DPU are housed within the spacecraft body. WAVES has onboard interconnects with 3-D PLASMA and with SWE.

See also the WAVES Homepage.


EPACT

Experiment Overview

    The Energetic Particle Acceleration, Composition, and Transport (EPACT) investigation will provide a comprehensive study of energetic particle acceleration and transport processes in solar flares, the interplanetary medium, and planetary magnetospheres, as well as the galactic cosmic rays and the anomalous cosmic ray component.

    EPACT measurements will determine elemental and isotopic abundances for the minor ions making up the solar wind, with energies in excess of 20keV. This direct sampling of solar matter is a way to study events on the solar surface and the incorporation of solar material into the solar wind. EPACT will also provide information on shocks in the interplanetary medium, which accelerate particles from solar-wind energies to several hundred keV.

Science Objectives

    To study acceleration, composition and transport of energetic particle populations, including particles from solar flares, particles accelerated in interplanetary shocks, and the anomalous component and galactic cosmic rays.

Measurement Objectives

    To provide:
    • Energy spectra of electrons and atomic nuclei of different charge and isotopic composition, from hydrogen to iron, over an energy range extending from 0.1 to 500 MeV/nucleon.
    • Isotopic composition of medium energy particles (2 - 50 MeV/nucleon) in solar flares, in the anomalous component and in galactic cosmic rays, extending up to Z = 90.
    • Determination of angular distributions of these fluxes.

Description of Instrument

    The EPACT instrument consists of three integrated telescope/electronics boxes mounted on the body of the spacecraft. The extensive dynamic range of particles to be measured is divided between three Low Energy Matrix Telescopes (LEMT), two Alpha-Proton-Electron Telescopes (APE), an Isotope Telescope (IT), and a Supra Thermal Energetic Particle Telescope (STEP). The APE and IT instruments are contained in a single package known as the Electron Isotope Telescope (ELITE). These solid state detector telescopes all use the dE/dx by E method of particle identification, except STEP, which obtains particle mass by measuring time-of flight and energy. An onboard recorder allows continuous observations to be made.

SWE

Experiment Overview

    The Solar Wind Experiment (SWE) will measure ions and electrons in the solar wind and the foreshock regions (particles whose energies are in the kiloelectronvolt range). From these measurements, the solar wind velocity, density, temperature and heat flux can be deduced. Electron and ion velocity distributions should reveal properties of the following plasmas and their pivotal role in the transfer of mass, momentum, and energy from the Sun to the Earth. Measurements made in the foreshock region will contribute to understanding the structure of the bow shock.

    See also the Solar Wind Experiment Homepage.

Science Objectives

    To study the solar wind and its fluctuations and the interaction of the solar wind with the magnetospheric system.

Measurement Objectives

    To provide:
    • High time-resolution 3-D velocity distributions of the ion component of the solar wind, for ions with energies ranging from 200 eV to 8.0 keV.
    • High time-resolution 3-D velocity distributions of subsonic plasma flows including electrons in the solar wind and diffuse reflected ions in the foreshock region, with energies ranging from 7 eV to 22 keV.
    • High angular resolution measurements of the "strahl" (beam) of electrons in the solar wind, along and opposite the direction of the interplanetary magnetic field, with energies ranging from 5 eV to 5 keV.

Description of Instrument

    The SWE instrument consists of fve integrated sensor/electronics boxes and a data processing unit (DPU). The sensor units are mounted on the top and bottom shelves of the spacecraft, extending through the top and bottom surfaces.

    3D velocity distribution measurements of the ion component in the solar wind are made by a pair of Faraday Cup analyzers, which provide a wide field-of-view and the capability for flow characterizatbn within one spin revolution (3 seconds). 3D velocity distribution measurements of ions and electrons in plasmas having Mach numbers <1 are made using six cylindrical electrostanic deflection analyzers, called Vector Electron Spectrometers (VEIS), arranged in two triaxial sets.

    A toroidal electrostanic analyzer with channelplate detectors functions as the strahl sensor, measuring electron velocity distribution and pitch angle. An ultra-violet calibration unit for the VEIS is mounted inside the spacecraft with the DPU.


SMS

Experiment Overview

    The Solar Wind and Suprathermal Ion Composition Studies (SWICS/MASS/STICS) experiment comprises three major instruments: Solar Wind Ion Composition Spectrometer (SWICS), High Mass Resolution Spectrometer (MASS), and Suprathermal Ion Composition Spectrometer (STICS). This experiment will determine the abundance, composition and differential energy spectra of solar wind ions, and the composition, charge state and 3-D distribution functions of suprathermal ions. These ions and their abundance fluctuations provide information about events on the solar surface and the formation of the solar wind, complementing the EPACT and 3D-PLASMA investigations.

Science Objectives

    To provide the instantaneous characteristics of matter entering the Earth's magnetosphere, determine solar abundances, characterize physical properties of the acceleration regions in the lower corona, and study the following processes: physical processes in the solar atmosphere, plasma processes affecting solar wind kinetic properties, solar wind acceleration, interplanetary acceleration mechanisms, and interstellar ion pick-up processes.

Measurement Objectives

    To obtain the following measurements:
    • Energy, mass and charge composition of major solar wind ions from H to Fe, over the energy range from 0.5 to 30 keV/e. (SWICS)
    • High mass-resolution elemental and isotopic composition of solar wind ions from He to Ni, having energles from 0.5 to 12 keV/e. (MASS)
    • Composition, charge state and 3-D distribution functions of suprathermal ions (H to Fe) over the energy range from 8 to 230 keV/e. (STICS)

Description of Instrument

    The SMS experiment consists of five separate packages mounted on the spacecraft body. SWICS uses electrostatic deflection, post-acceleration, and a time-of-flight vs. energy measurement to determine the energy and elemental charge state composition of solar wind ions.

    MASS uses energy/charge analysis followed by a time of flight measurement, to determine solar-wind ion composition with high mass-resolution (M/delta M > 100), for the first time.

    STICS, similar to SWICS but not using post-acceleration, has a large geometric factor and wide angle viewing for studies of suprathermal ions.

    The SMS data processing unit and STICS analog electronics unit are mounted separately.


MFI

Experiment Overview

    The Magnetic Fields Investigation (MFI) will investigate the large-scale structure and fluctuation characteristics of the interplanetary magnetic field, which influence the transport of energy and the acceleration of particles in the solar wind and dynamic processes in the Earth's magnetosphere. The fundamental observations of solar wind magnetic fields are important to the study of the solar wind and magnetosphere coupling process and also to the interpretation of other observational data from WIND.

Science Objectives

    To establish the large-scale structure and fluctuation characteristics of the interplanetary magnetic field as functions of time, and through correlative studies to relate them to the dynamics of the magnetosphere.

Measurement Objectives

    To provide:
    • Accurate, high resolution vector magnetic field measurements in near real time on a continuous basis.
    • A wide dynamic measuring range, from +/- 0.004 nT up to +/- 65,536 nT, in eight discrete range steps.
    • Measurement rates up to 44 vector samples per second for analysis of fluctuations.
Description of Instrument
    The MFI instrument consists of dual triaxial fluxgate rnagnetometers mounted on a 12-meter radial boom, and a data processing and control unit within the body of the spacecraft. The magnetometer sensors each produce analog signals proportional to the strength of the magnetic field component aligned with the sensor. These signals are then digitized and processed by a microprocessor controlled data system. Mounting the magnetometers at the outboard end and at an inboard location on the boom helps substantially to reduce contamination of the measurements by spacecraft-generated magnetic fields. MFI has a very wide field measurement capability, from +/- 0.004 nT to +/- 65,536 nT, with both automatic and commandable range-change capability. Measurement rates are: one vector per 92 seconds for key parameter data, 10.9 vectors per second for rapid data for standard anatysis, and 44 vectors per second for Fast Fourier Transform data, and data from the snap-shot memory which can be triggered automatically for predefined field changes.

    See also The Magnetic Fields Investigation Homepage


3D PLASMA

Experiment Overview

    The 3-D Plasma and Energetic Particle Analyzer investigation will measure ions and electrons in the interplanetary medium with energies including that of the solar wind and the energetic particle range. It will study the particles upstream of the bow shock in the foreshock region and the transient particles emitted by the Sun during solar particle events following solar flares. This experiment will cover the gap between the energy ranges covered by SWE and EPACT.

    For more information see the 3-D Plasma and Energetic Particle Homepage.

Science Objectives

    To explore the interplanetary particle population in the thermal and suprathermal energy range; to study the particle acceleration at the Sun, in the interplanetary medium, and upstream from the Earth; to study transport of particles and basic plasma processes in the interplanetary medium; and to measure the particle and plasma input to and output from the Earth's magnetosphere.

Measurement Objectives

    To obtain the following measurements:
    • The three dimensional distribution of plasma and energetic electrons and ions over the particle energy range from solar wind to cosmic ray energies, a few eV to several MeV.
    • Energy resolution of 0.20 (deltaE/E) and angular resolution from 3 eV to 30 keV; and energy resolution of 0.3 (deltaE/E) and angular resolution of 22.5 degrees X 36 degrees, for particals from 20 keV to 11 MeV.
    • Perturbations to the electron distribution function, in wave-particle interactions.

Description of Instrument

    The 3-D PLASMA instnument consists of two sensor packages mounted on small radial booms, and an electronics package mounted inside the spacecraft. One boom-mounted sensor package contains an array of 6 double-ended semiconductor telescopes, each with two or three closely sandwiched silicon detectors to measure ebctrons and ions above 20 keV. One side of each telescope is covered with a thin foil which absorbs ions below 400 keV. On the other side, the incoming electrons below 400 keV are swept away by a magnet so that electrons and ions are cleanly separated. Higher energy electrons (up to ~1 MeV) and ions (up to 11 MeV) are identified by the two double-ended telescopes which have a third detector. The first sensor package also contains a pair of ion electrostatic analyzers (PESA-L and -H) for measuring ion fluxes from ~3 eV to 40 keV. The second sensor package contains a pair of electron electrostatic analyzers (EESA-L and -H) for measuring electron fluxes from ~3 eV to 30 keV, and for making input (from EESA-H) to a fast particle correlator (FPC). The FPC, using also plasma wave data from WAVES as input, measures perturbations to the electron distribution function and studies other wave-particle interactions.

TGRS

Experiment Overview

    The Transient Gamma-Ray Spectrometer (TGRS) will detect transient gamma-ray burst events and will make the first high-resolution spectroscopic survey of cosmic gamma-ray bursts, and will also make measurements of gamma-ray lines in solar flares.

    Cosmic gamma-ray bursts are among the most violent and energetic processes known to exist in nature, characteristically emitting most of their luminosity at gamma-ray wavelengths. The high-resolution spectroscopy of solar flares will contribute to the study of solar flare activities and help in understanding the coupling between the active corona and photosphere.

    For additional information see the TGRS Home Page.

Science Objectives

    To provide the first high resolution spectroscopic survey of cosmic gamma-ray bursts and the first high-resolution spectroscopy of solar flares, and search for possible diffuse background lines and monitor the 511 keV positron annihilation radiation from the galactic center.

Measurement Objectives

    To obtain:
    • Spectroscopic measurements of transient gamma-ray events, in the energy range from 15 keV to 10 MeV.
    • Energy resolution of 2.0 keV @ 1.0 MeV (E/delta E = 500).
    • Monitoring of the time variability of the 511 keV line emission from the galactic center, on time scales from ~2 days to >1 year.

Description of Instrument

    The TGRS instrument consists of four assemblies: detector cooler assembly, pre-amp, and analog processing unit, all mounted on a tower on the +Z end of the spacecraft, and a digital processing unit mounted in the body of the spacecraft. The detector is a 215 cubic cm high purity n-type germanium crystal of dimensions: 6.7 cm (diameter) X 6.1 cm (length), radiatively colled to 85 degrees K. The germanium serves as a reaction medium for incoming gamma rays, which, depending on their energy, are either stopped by or passed through the detector crystal. Particle energy and angle of incidence are calculated based on a number of primary and secondary interaction processes, including photoelectric, Compton, pair and bremsstrahlung radiation as well as the ionization energy losses of secondary electrons. A two-stage cooler surrounds the detector, providing a field of view of 170 degrees. Gamma-ray bursts and solar flares are expected to be detected at a frequency of several per week, with typical durations between 1 second and several minutes. Between bursts the instrument is maintained in a waiting mode, measuring background counting rates and energy spectra. When a burst or flare occurs, the instrument switches to a burst mode, where each event in the detector is pulse-height analyzed and time tagged in a burst memory. Then the instrument switches to a dump mode for reading out the burst memory.

KONUS

Experiment Overview

    The Gamma Ray Burst Studies investigation will perform gamma-ray burst studies similar to the TGRS studies. It will perform event detection and will measure time history and energy spectra. Although KONUS has a lower resolution than TGRS, it has broader area coverage to complement that of TGRS so that, when their data are combined, they provide coverage of the full sky. KONUS is the first Russian instrument to fly on an American satellite since civil space cooperation between the U.S. and Russia was resumed in 1987.

Science Objectives

    To continuously monitor cosmic gamma-ray bursts and solar flares in the energy range 10keV to 10 MeV.

Measurement Objectives

    To obtain:
    • Measurement of gamma-ray burst energy spectra over the energy range 10 keV to 10 MeV, with energy resolution E/deltaE = 15 @ 200 keV.
    • Measurement of burst time histories in three energy ranges covering 10 to 770 keV.
    • High-time-resolution measurement (2 ms resolution) for the high-intensity sections of a burst time history.
    • Continuous measurement of the gamma- and cosmic ray background, interrupted only to read out bursts.

Description of Instrument

    The Konus instrument consists of two Russian sensors mounted on the top and bottom of the spacecraft aligned with the spin axis, a U.S. interface box, and a Russian electronics package mounted in the spacecraft body. The sensors, copies of ones successfully flown on the Soviet COSMOS, VENERA and MIR missions, are identical and interchangeable Nal scintillation crystal detectors of 200 cm2 area, shielded by Pb/Sn. The design and location of the two sensors ensure practically isotropic angular sensitlvity. The relative count rates recorded by the two detectors can provide a burst source locus to within a few degrees relative to the spin axis. On-board analysis of background and burst events is performed by four pulse height analyzers, four time history analyzers, two high resolution time history analyzers and a background measurement system.

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