The Focusing Optics X-ray Solar Imager (FOXSI) is the first solar-dedicated NASA-sounding rocket experiment that performs imaging spectroscopy in hard X-rays (HXRs) using direct focusing techniques. FOXSI has improved the sensitivity and imaging dynamic range by orders of magnitude compared to its predecessors (e.g., RHESSI), demonstrated in three successful flights (2012, 2014, and 2018). FOXSI is currently funded to fly a fourth time in NASA’s first solar flare campaign. The FOXSI rocket payload is a pathfinder to indicate the sort of scientific accomplishments that a solar-dedicated spacecraft based on this technology could achieve in the future. 

For more, see the FOXSI research overview webpages.