Japan's Hayabusa2 Sets July 5 for a 5 km/s Flyby of Asteroid Torifune, a Dress Rehearsal for Its 2031 Visit to 1998 KY26
JAXA's extended Hayabusa2 mission will pass roughly 1 km from asteroid Torifune at 5 km/s on July 5, testing guidance for planetary defense.
Overview
Japan’s Hayabusa2 spacecraft is scheduled to make a high-speed flyby of the near-Earth asteroid Torifune on July 5, 2026, passing approximately 1 km from the body at a relative velocity of 5 km/s, according to a JAXA press release dated June 9. The encounter is the first major science target of the probe’s extended mission and is designed as much to rehearse precision navigation as to study a new world.
The Japan Aerospace Exploration Agency says the pass is timed for around 18:30 JST, with the caveat that “the time may vary depending on operational conditions,” per JAXA.
What We Know
Hayabusa2 completed its primary mission when it delivered its sample capsule back to Earth on December 6, 2020, according to JAXA/ISAS. That capsule carried approximately 5.4 grams of material from asteroid 162173 Ryugu, as reported by New Space Economy. JAXA subsequently approved an extended mission, designated Hayabusa2♯ (“Hayabusa2 sharp”), and redirected the spacecraft toward new targets, per JAXA/ISAS.
The July target, Torifune, carries the former designation 2001 CC21 and the formal number (98943), according to a mission overview paper led by Masatoshi Hirabayashi and Masahiko Hayakawa and posted to arXiv. That paper states the asteroid’s equivalent diameter is approximately 450 m, with an earlier taxonomic class reported as L-type while other spectral observations suggested it belongs to the S-complex. It cites a measured rotation period of 5.02124±0.00001 hours; ISAS describes the spin as approximately five hours and notes “indications that the shape may be elongated,” per JAXA/ISAS.
The flyby geometry is demanding. The overview paper specifies that “the flyby speed is planned to be 5.25 km/s, while the encounter location is 0.81 au from the sun,” and that the reference flyby distance from the asteroid’s center is 1–10 km, according to arXiv. Observations will use the spacecraft’s onboard instruments — the ONC-T and ONC-W1 optical cameras, the TIR thermal infrared imager, the NIRS3 spectrometer, and LIDAR, per arXiv. ISAS notes the cameras have a fixed orientation, so imaging will run up to just before closest approach, according to JAXA/ISAS.
JAXA frames the pass primarily as a technology demonstration. The flyby “aims to demonstrate high-precision orbital guidance and develop technology applicable to implementing intentional orbit changes to an asteroid,” and will “acquire fundamental data for the technology required to accurately guide a probe to impact with small celestial bodies,” according to JAXA. ISAS adds that the mission serves “not only [to] further planetary science through the study of a new asteroid, but also serves to support planetary defense,” echoing the kind of kinetic-impact targeting NASA demonstrated with its 2022 DART test, per JAXA/ISAS.
The Longer Mission
Torifune is a waypoint, not the destination. Hayabusa2 is scheduled to reach asteroid 1998 KY26 in 2031 to conduct what JAXA calls a world-first rendezvous, with the agency listing the target as roughly 30 m in diameter, according to JAXA.
That final leg carries some uncertainty. Newer measurements suggest 1998 KY26 is only about 11 meters wide and rotating once every roughly five minutes — smaller and faster-spinning than earlier estimates — and its smaller size, faster rotation, and higher albedo present challenges for mission operations, according to Universe Today. The spacecraft retained about 30 kg of xenon propellant for its ion drives, and Universe Today notes Hayabusa2 will be near the end of its fuel when it arrives, making propellant efficiency critical, per Universe Today.
What We Don’t Know
JAXA has cautioned that the exact flyby time may shift with operations, and the precise closest-approach distance is still being finalized within the 1–10 km reference range, according to JAXA/ISAS. It also remains to be seen how much surface detail the cameras can resolve during a pass at more than 5 km/s, and whether the revised, smaller dimensions of 1998 KY26 will force changes to the 2031 rendezvous plan flagged by Universe Today.