NASA's HESSI mission, which involves the work of OU scientists, was successfully launched at 2100 UT on 5th February 2002. HESSI - the High Energy Solar Spectroscopic Imager - is on a mission to explore the basic physics of particle acceleration and explosive energy release in solar flares. For the past 3 years Dr Andrew Conway, Lecturer in the Open University's Department of Physics and Astronomy, has been working on the imaging capabilities of HESSI as well as the theory of how energetic particles are produced in solar flares. He and PhD student Ben Eves, co-supervised with Dr Andy Norton, will now be able to analyse observations of solar flares from HESSI and test whether these theories are correct.