The High Energy Solar Spectroscopic Imager (HESSI) Small Explorer mission for
the next (2000) solar maximum
R.P. Lin and the HESSI team
Physics Department. & Space Sciences Lab
University of California
Berkeley, California
The primary scientific objective of the NASA High Energy Solar Spectroscopic
Imager (HESSI) Small Explorer mission is to investigate the physics of particle
acceleration and energy release in solar flares. Observations will be made of
X-rays and gamma-rays from ~3 keV to ~20 MeV with an unprecedented combination
of high resolution imaging and spectroscopy. The HESSI instrument utilizes
Fourier-transform imaging with 9 bi-grid rotating modulation collimators and
cooled germanium detectors. The instrument is mounted on a Sun-pointed spin-
stabilized spacecraft and placed into a 600 km-altitude, 38 degree inclination
orbit. It will provide the first imaging spectroscopy in hard X-rays, with ~2
arcsecond angular resolution, time resolution down to tens of ms, and ~1 keV
energy resolution; the first solar gamma-ray line spectroscopy with ~1-5 keV
energy resolution; and the first solar gamma-ray line and continuum imaging,
with ~36 arcsecond angular resolution. HESSI is planned for launch in July
2000, in time to detect the thousands of flares expected during the next solar
maximum.