- SSJ/4/5 (Precipitation Electron/Proton Spectrometer) Objective: Measurement of transfer
energy, mass, and momentum of charged particles through the magnetosphere-ionosphere
in the Earth's magnetic field. The instrument looks up toward the satellite zenith.
- The SSJ/4 sensor consists of four electrostatic analyzers that record the flux of
precipitating ions or electrons at 20 fixed energy channels between 30 eV and 30 keV.
The curved plate detectors allow precipitating electrons and ions to enter through
an aperture of about 20 x 10 (FWHM). Electrons and ions of the selected energy are
deflected toward the target by an imposed electric field applied across the two plates.
The two low energy detectors consist of 10 channels centered at 34, 49, 71, 101, 150,
218, 320, 460, 670, and 960 eV. The high energy detector measures particles in 10
channels centered at 1.0, 1.4, 2.1, 3.0, 4.4, 6.5, 9.5, 14.0, 20.5 and 29.5 KeV. Each
detector integrates each channel for 0.09 s from high energy channel to low. A complete
cycle is sampled each second. The primary sources of the particles precipitating into
the upper atmosphere are the northern and southern auroral zones.
- SSI/ES (Special Sensor Ionospheric Plasma Drift/Scintillation Monitor) Objective:
Measurement of the ambient electron density and temperatures, the ambient ion density,
and the average ion temperature and molecular weight at the DMSP orbital altitude.
The instrument consists of an electron sensor (Langmuir probe) and an ion sensor mounted
on a 2.5 meter boom. The ion sensor is a planar aperture, planar collector sensor
oriented to face the spacecraft velocity vector at all times. In addition to the Langmuir
probe and planar collector which make up the SSI/E, the SSI/ES has a plasma drift
meter and a scintillation meter.
- SSM (Special Sensor Magnetometer), a triaxial fluxgate magnetometer. The SSM measures
geomagnetic fluctuations associated with solar geophysical phenomena (i.e., ionospheric
currents flowing at high latitudes). In combination with the SSI/ES and the SSJ/4,
the SSM provides heating and electron density profiles in the high-latitude ionosphere.
SSM takes and reports 12 readings/s for the Y and Z axes. Only 10 readings of the
12 readings per second are reported for the X axis due to telemetry limitations. The
SSM's axes are aligned with the spacecraft's axes where X is downward and aligned
to local vertical within 0.01 degree, Y is parallel to the velocity vector for spacecraft
with ascending node in the afternoon/evening sector, and Z is away from the solar
panel and anti-parallel to the orbit normal vector.) The measurement range is A?65535
nT for each axis, with a one-bit resolution of 2 nT. Note: The magnetic field has
three sources: 1) the magnetic field from the solid Earth, 2) the magnetic field from
electrical currents flowing in the ionosphere and magnetosphere, and 3) the magnetic
field from the spacecraft. Measurement of source 2 is the principal objective of the
SSM, the measurement of source 1 is a secondary objective, and measurement of source
3 is a nuisance which is eliminated from the data as much as possible during data