The first TLE found in the UHU project-related observations made from the ISS

During preliminary quality checks of the videos recorded during Axiom Space’s Ax-4 mission in the framework of the UHU Earth Observation experiment, we identified two distant ELVES (ring-shaped transient luminous event), captured by Ax-4 mission commander Peggy Whitson on July 4 while flying over the Philippines and Eastern Indonesia.

These are the first lightning-related optical flashes (transient luminous events, or TLEs) observed within the framework of the UHU experiment. We expect to see more TLEs but a thorough review of the available footage — along with the search for additional TLEs — will still require time. Even at this stage, however, we can already say that the UHU experiment will not end without results: beyond the identified ELVES, numerous lightning flashes are clearly visible in the video frames.

ELVES (the red flash below the green airglow) and the light from the triggering lightning stroke beyond the horizon, captured on July 4, 2025. Frame detail (color-enhanced) from a video recorded by Commander Peggy Whitson aboard the International Space Station, flying over the Philippines and Eastern Indonesia. In the foreground, part of the robotic arm of the ISS is visible.

For more details on the UHU, please see the webpage of the project.