Japan’s H3 Rocket Likely Made 1.5 Trips Around Earth; Analyst Believes Satellite Almost Certainly Lost As Well

By Keiichi Nakane / Yomiuri Shimbun Correspondent

16:02 JST, December 25, 2025

WASHINGTON — Japan’s No. 8 H3 rocket likely reentered the atmosphere over South America about two hours after launch, according to analysis by Dr. Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics.

The Monday launch of the H3 rocket ended in failure. The Cabinet Office’s Michibiki No. 5 positioning satellite was aboard and is also believed to have been lost.

McDowell calculated the rocket’s trajectory using flight altitude and velocity data released by the Japan Aerospace Exploration Agency (JAXA). The rocket was launched at 10:51 a.m. Japan time on Monday, and it likely reentered the atmosphere somewhere over Brazil or Argentina around 1 p.m. the same day, after making 1½ orbits around the Earth.

Its speed before atmospheric reentry was about 27,000 kph, below the roughly 28,000 kph needed to maintain Earth orbit.

According to JAXA, the second-stage engine of the rocket ceased burning about five minutes earlier than planned. The Education, Culture, Sports, Science and Technology Ministry and JAXA have established a task force to investigate the cause of the failure and how the satellite became separated from the rocket.

In an interview with The Yomiuri Shimbun, McDowell said that even if the satellite had separated successfully, it likely reentered the atmosphere as well, because its orbit is nearly identical to the rocket’s.

It is 99% certain that the rocket and satellite fell into the atmosphere, he said.