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HESSI
(High Energy Solar Spectroscopic Imager)
The High Energy
Solar Spectroscopic Imager (HESSI), a SMEX
mission currently scheduled for launch in October, 2001. HESSI
is designed to study the hard X-ray/gamma-ray continuum and gamma-ray lines that are
the direct signatures of energetic electrons and ions, respectively,
at the Sun. HESSI combines an imaging system consisting of 9 rotating
modulation collimators (RMCs), with a high-resolution spectrometer
consisting of 9 germanium detectors covering energies from soft
X-rays (3 keV) to high-energy gamma-rays (20 MeV). HESSI's hard
X-ray imaging spectroscopy provides spectral resolution of ~1 keV,
spatial resolution down to ~2 arcsec, and temporal resolution as
short as tens of milliseconds.
The goal of our program at UNH is to measure the angular distribution
of the accelerated electrons by performing measurements of the hard
X-ray polarization of solar flares. An important advantage of polarization
measurements is the ability to derive, from measurements by a single
instrument, the beaming (or anisotropy) of particle distributions
for a single flare. Measurements with sufficient temporal resolution
can even measure the evolution of the anisotropy in the particle
distributions. We will be using HESSI to perform hard X-ray polarimetry of
solar flares (and perhaps other cosmic sources). Coupled with the
other data obtained by HESSI, this will offer a unique opportunity
to probe solar flare particle acceleration processes.
For further information on the HESSI mission itself check
out the following web sites:
- The HESSI Home
Page at Goddard Spaceflight Center
- The HESSI Home Page
at UC Berkeley
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