Japan’s H3 suffers second-stage anomaly, QZS-5 satellite lost

HELSINKI — Japan’s flagship H3 rocket suffered an issue with its second stage late Sunday resulting in the loss of the Michibiki 5 (QZS-5) navigation satellite.

The H3 rocket lifted off at 8:51 p.m. Eastern Dec. 22 (0151 UTC, Dec. 23) from Tanegashima Space Center carrying the Michibiki 5 (Quasi-Zenith Satellite System 5 (QZS-5)) satellite. The liquid hydrogen and liquid oxygen first stage performed nominally, but issues with the second stage meant the satellite was not inserted into its intended geosynchronous transfer orbit. 

A Japan Aerospace Exploration Agency (JAXA) press release later stated that the second stage engine’s second ignition failed to start normally and shut down prematurely. As a result QZS-5 could not be put into the planned orbit and the launch failed.

A post-launch press conference revealed that the first second stage engine cutoff occurred 27 seconds later than planned, while the second ignition was delayed by 15 seconds and terminated almost immediately after startup. Telemetry showed that hydrogen tank pressure in the second stage began falling during the first-stage burn, a behavior now under investigation.

It is unclear if the satellite separated from the launch vehicle. U.S. Space Force cataloged an object in a 109 by 441-kilometer orbit consistent with a launch from Tanegashima. The satellite and second stage are expected to reenter within a few orbits due to the low perigee.

JAXA stated that the agency has set up a special task force headed by JAXA president Yamakawa and investigations into the cause have been started. 

QZSS is Japan’s navigation satellite system, designed to provide positioning, navigation and timing services over Japan while augmenting GPS accuracy and reliability across the Asia-Pacific region. The Michibiki 6 (QZ-6) satellite was successfully sent to geostationary orbit in February.

The launch was the seventh for the 63-meter-long H3, Japan’s flagship launch designed to replace the older H-IIA and H-IIB rockets. It is also the second failure, following the loss of the first launch in March 2023, again due to a second stage issue. The rocket most recently launched the first HTV-X cargo spacecraft in October.

The failure will have potentially significant knock-on effects for Japan’s space sector. The expendable rocket was due to launch a further QZSS satellite and a second HTV-X in the coming year, among other launches. 

Notably, the Martian Moons eXploration (MMX) mission is scheduled to launch on an H3 in November-December 2026 during a short launch window to Mars. MMX was due to launch during the previous window in fall 2024, but the mission was delayed in part due to the failure of the first H3 launch. H3 is also slated to launch an asteroid mission for the United Arab Emirates, currently scheduled for 2028.

Sunday’s H3 launch was the third time the rocket flew this year, and the fourth Japanese launch overall in 2025. A number of Japanese payloads also flew on Rocket Lab Electron and SpaceX Falcon 9 rockets, including commercial firm ispace’s second moon lander.