Impact of the 1 April 2026 Artemis II Rocket Launch on the Upper Atmosphere: TIMED/GUVI Observations

Abstract The NASA Artemis II rocket was successfully launched at 06:35 p.m. ET (22:35 UTC) on 1 April 2026 from the Kennedy Space Center (28°35′28″N 80°39′03″W). The rocket plume caused enhanced Lyman α emission (up to ∼3 kR) observed by TIMED/GUVI on 2–6 April (5 days). Its peak intensity decreased linearly from April 3 at a rate ∼740 R/day. The half‐maximum width of the zonal Lyman α intensities at 20°–30° latitude (at ∼01:30 p.m. local solar time) increased from ∼3,000 km on April 2–∼9,000 km on April 6. GUVI also detected significant reductions in O‐130.4 nm and O‐135.6 nm radiances, indicating O density reduction. Weakly enhanced NO ε band intensity (NO density) was also observed on April 2 and 3. These features are due to photochemical processes associated with water vapor in the rocket plume and diffusion.