RHESSI SAMPEX

Explorer 81, Reuven Ramaty High Energy Solar Spectroscopic Imager

Mission Profile

RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager, Explorer 81) is a NASA solar observation satellite launched on 5 February 2002 to study the physical processes in solar flares by imaging and taking spectra of X-ray and gamma-ray emissions from 3 keV to 17 MeV. Its rotating modulation collimator system allowed unprecedented imaging of hard X-ray and gamma-ray emission from flares at arcsecond resolution, revealing the locations of particle acceleration and energy deposition in the solar atmosphere. RHESSI discovered that antimatter (positrons) is routinely produced in major solar flares and provided the most detailed measurements of the gamma-ray spectroscopy of solar energetic particle events. The mission was decommissioned in 2018 after 16 years of operation.