| The Space Environment Monitor (SEM) instrument package on-board all GOES satellites
has provided magnetometer, energetic particle, and soft X-ray data continuously since
July 1974. Usually two GOES satellites operate at the same time in the Earth’s equatorial
plane. They travel in geosynchronous orbit (6.6 Earth radii) and are generally located
at 75 and 135 degrees west longitude. This trajectory allows the detectors an unobstructed
view of the sun for all but the few hours per year, around equinox and near midnight,
when the Earth eclipses the sun. Higher resolution values for allthree sensors are
averaged for each 5.0 minutes, which permits one month of data from one satellite
to be stored on a single high density, IBM compatible, diskette (5.25" or 3.5"). Solid
state detectors with pulse height discrimination measure protons from 0.8 to 500 MeV,
alpha particles from 4.0 to 392 MeV,and electrons with kinetic energies greater than
or equal to 2.0 MeV. Because charged particles in these energy ranges, accelerated
in solar flares, can reach the vicinity of Earth in large numbers,they pose a hazard
to satellites, manned space flight and to high-altitude aircraft. They also significantly
affect the high-latitude ionosphere and may cause magnetic storms. See Entry_ID =
G00036 for digital data.
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