Synonymous Platform Names:
Reuven Ramaty High Energy Solar Spectroscopic Imager
LEO > Low Earth Orbit > Polar Sun-Synchronous
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The High Energy Solar Spectroscopic Imager (HESSI) mission consists of a single
spin-stabilized spacecraft in a low-altitude orbit inclined 38 degrees to the
Earth's equator. The only instrument on ... board is an imaging spectrometer with
the ability to obtain high fidelity color movies of solar flares in X rays and
gamma rays. It uses two new complementary technologies: fine grids to modulate
the solar radiation, and germanium detectors to measure the energy of each
photon very precisely. The HESSI was renamed the Reuven Ramaty High Energy
Solar Spectroscopic Imager (RHESSI). RHESSI is a NASA Small Explorer satellite
and was launched February 5, 2002.
RHESSI's imaging capability is achieved with fine tungsten and/or molybdenum
grids that modulate the solar X-ray flux as the spacecraft rotates at ~ 15 rpm.
Up to 20 detailed images can be obtained per second. This is sufficient to
track the electrons as they travel from their acceleration site, believed to be
in the solar corona, and slow down on their way to the lower solar atmosphere.
The high-resolution spectroscopy is achieved with 9 cooled germanium crystals
that detect the X-ray and gamma-ray photons transmitted through the grids over
the broad energy range of 3 keV to 20 MeV. Their fine energy resolution of
about 1 keV is more than sufficient to reveal the detailed features of the
X-ray and gamma-ray spectra, clues to the nature of the electron and ion
For more information, see;
Cape Canaveral/Kennedy Space Center, USA