What is FOXSI?
The Focusing Optics X-ray Solar Imager (FOXSI) is a sub-orbital rocket project with four successful launches (and gearing up for a fifth in 2026!) It is the first solar-dedicated instrument to observe hard X-rays using focusing optics. Direct imaging enables the experiment to study solar X-ray radiation with enhanced sensitivity and dynamic range, exploring issues of energy release and particle acceleration in the corona—the outermost layer of the Sun.
FOXSI-4
The rocket’s fourth launch successfully occurred in April 2024 at Poker Flat Research Range in Alaska as part of NASA's first-ever solar flare campaign. Two experiments flying on two different rockets -- Hi-C and FOXSI-4 -- observed an M1 class solar flare simultaneously.
FOXSI-5
The FOXSI-4 experiment was recovered successfully a few days after the launch, although it had a harsh landing. (You try landing on the side of an Alaskan mountain and see how you feel...) The team took apart everything and tested it...and immediately started reassembling for another flight. FOXSI-5 is a reflight of FOXSI-4 with a few touch-ups. The experiment is planned to fly from the White Sands Missile Range with a launch campaign arranged over clusters of a few days in 2026. FOXSI-5 is led by Dr. Juan Camilo Buitrago-Casas from the University of California at Berkeley.