Japan and China both checked off asteroid milestones over the weekend, with one spacecraft squeezing more science out of an old sample-return mission and another beginning the hard part of a new one.
Japan’s space agency, JAXA, said Hayabusa2 successfully flew close to 98943 Torifune on Sunday, years after the spacecraft had already delivered asteroid material to Earth. Hours later, the China National Space Administration released imagery from Tianwen-2 after the probe reached the near-Earth asteroid 469219 Kamoʻoalewa.
The two encounters are very different missions. Hayabusa2 is doing bonus work after its main job ended in 2020. Tianwen-2 is at the start of a sample-collection campaign that China says should send material back to Earth late next year.
Hayabusa2 gets another target
Hayabusa2 launched in December 2014 and reached the near-Earth asteroid 162173 Ryugu in June 2018. After collecting samples there, the spacecraft used its ion engines to head back toward Earth. During a 2020 flyby, it released a return capsule that was later recovered with 5.4 grams of asteroid material, according to JAXA mission results cited in the report.
The spacecraft had more life left than a one-and-done mission needed. Its propulsion system still carried about 30 kilograms of xenon, from an original load of 66 kilograms. That gave JAXA engineers enough margin to plan a long extension with two additional asteroid visits.
The first of those was Torifune, a roughly 450-meter-long object described as peanut-shaped. JAXA began observations about two weeks before the encounter. The flyby brought Hayabusa2 to within about 10 kilometers of the asteroid.
JAXA said the spacecraft kept observing Torifune until shortly before closest approach, but could not continue once it had passed the asteroid. The agency said only some instrument data has come down so far, with the rest expected during later communications sessions.
If the spacecraft keeps behaving, Hayabusa2’s next planned stop is 1998 KY26, a much smaller near-Earth object believed to be about 11 meters across. That encounter is scheduled for July 2031 under the current mission plan.
Tianwen-2 arrives at a quasi moon
China’s Tianwen-2 reached within 20 kilometers of Kamoʻoalewa on July 2, the China National Space Administration said. The agency released an image of the asteroid that shows a small, irregular body with a shape loosely resembling an arrowhead.
Kamoʻoalewa is only about 20 meters across. It is often called a quasi moon because it travels around the Sun with an orbital period similar to Earth’s, about 365 days, and moves ahead of Earth. It is not bound by Earth’s gravity. At its closest, it comes within about 4.6 million kilometers of Earth, more than 10 times the distance to the Moon.
CNSA said Tianwen-2’s arrival starts more detailed work to measure the asteroid’s shape, composition, rotation and other properties. After that survey, the spacecraft is expected to try to collect samples.
China has set a tentative November 2027 return date for the sample capsule. If that succeeds, CNSA has outlined an extended mission in which Tianwen-2 would travel to 311P/PanSTARRS and orbit it. That object has tails, which makes it a candidate for comet-like behavior, according to the Chinese plan described for the mission.
This story draws on original reporting from Ars Technica.
