Hayabusa2 Targets 11-Meter Asteroid 1998 KY26 for 2031 Landing as Final Planetary-Defense Mission

Q: Is a Japanese probe about to uncover a 43-year-old Soviet secret hidden in an asteroid's orbit?

Possibly—but not yet. Hayabusa2 is not about to prove a Soviet secret now; its potentially decisive test comes in July 2031, when the Japanese probe is scheduled to rendezvous with the tiny object 1998 KY26. The reason for the speculation is a recent hypothesis that 1998 KY26 may not be a natural asteroid at all, but the lost Soviet Phobos 1 spacecraft, which failed in 1988 after a faulty command upload. If that idea were correct, Hayabusa2 would be inspecting a 43-year-old relic of the Soviet space program. There is some evidence behind the claim. Researchers have argued that 1998 KY26’s estimated size, about 11 meters, unusually high reflectivity, rapid spin, and elongated shape could fit a derelict spacecraft better than a typical small asteroid. They also say the object’s orbit could be made compatible with Phobos 1 through plausible maneuvers within the probe’s capabilities. But this remains a minority, unproven interpretation. The mainstream view is still that 1998 KY26 is a natural small body, possibly a “dark comet” showing non-gravitational acceleration without obvious outgassing. Hayabusa2’s close-up observations should be able to distinguish between a rocky object and an artificial one. For now, the answer is that Hayabusa2 is heading toward an object that some scientists suspect could hide a Soviet-era secret, but the claim is speculative and will not be settled until the 2031 encounter.

3 articles · Updated · Hackaday · Jul 15

Japan’s Hayabusa2 is now slated to investigate 11-meter asteroid 1998 KY 26 in July 2031, with plans to enter orbit, deploy its last target marker and projectile, and attempt a landing near a pole.
The extended mission follows an early-July flyby of 450-meter asteroid 98943 Torifune, where Hayabusa2 passed within 800 meters at about 5 km/s and gathered close-up surface data despite tracking limits.
That 2031 encounter will test a spacecraft launched in 2014 and already past its 2020 sample-return mission, as radiation-damaged sensors and depleted ion engines raise the difficulty of another close asteroid operation.
The KY 26 mission is expected to be Hayabusa2’s last and could yield data useful for planetary defense as well as for understanding the behavior and diversity of very small near-Earth asteroids.