22.02.2025

Render of the Tianwen-2 near-Earth asteroid/comet orbiter spacecraft. Credit: CNSA

HELSINKI — The spacecraft for China’s Tianwen-2 combined near-Earth asteroid sample return and comet rendezvous mission has arrived at Xichang spaceport for launch preparations.

The Tianwen-2 spacecraft arrived at Xichang Satellite Launch Center in Sichuan province, southwest China, Feb. 20, according to a statement from the China National Space Administration (CNSA). 

CNSA stated vaguely that the launch is scheduled to be carried out in the first half of this year. The mission was previously stated by officials to launch around May 2025 on a Long March 3B rocket.

Tianwen-2 will first target near-Earth asteroid Kamoʻoalewa (2016 HO3), considered a quasi-satellite of Earth due to its co-orbital dynamics. It aims to collect samples from the roughly 40 to 100-meter-diameter asteroid and deliver them to Earth around 2027. Kamoʻoalewa is possibly a chunk of the moon blasted into space following an impact event, according to researchers.

The main spacecraft will then head for main-belt comet 311P/PANSTARRS, which has asteroid-like orbital characteristics but also features comet-like activity.

The two mission phases aim to provide insight into the composition and evolution of near-Earth objects and understand distribution of water and organic molecules and the history of the early solar system.

“The launch site facilities are in good condition, and the pre-launch test preparations are being carried out in an orderly manner as planned,” the statement read.

Sampling Kamoʻoalewa

Tianwen-2 will use two sampling techniques to collect material from the asteroid. These will be the touch-and-go (TAG) approach used by both NASA’s OSIRIS-REx and JAXA’s Hayabusa2, and an anchor-and-attach system featuring drills at the tips of landing legs. 

Early proposals for the mission, then named Zheng He for the Chinese admiral and explorer born in the 14th Century, indicated the spacecraft would aim to collect between 200 and 1,000 grams of samples.

Analysis of the samples aims to reveal the nature and origin of the asteroid, analyze its mineral content and provide comparisons with other asteroids. 

While China has conducted two successful sample return missions from the moon’s near and far sides with Chang’e-5 and last year’s Chang’e-6 mission, the velocity of the reentry module will be greater, adding new challenges. The China Aerospace Science and Technology Corporation (CASC) conducted high-altitude parachute deployment tests for the mission in 2023. In contrast to the lunar sampling missions, Kamoʻoalewa will have negligible gravity, requiring different approaches to settling on the body and obtaining samples.

China’s first excursion to an asteroid was a flyby of 4179 Toutatis in 2012, when the Chang’e-2 lunar orbiter made the pass as an extended mission objective. 

Comet rendezvous

Delivering samples to Earth will not be the end of the mission. The spacecraft will release a return module which will reenter the atmosphere, but also use the approach to the planet for a gravitational slingshot maneuver. This will send the main spacecraft on its way to the main-belt comet 311P/PANSTARRS, with arrival scheduled for around 2034.

The comet is seen as an ideal target for studying transitional objects between asteroids and comets. It orbits between 1.94 and 2.44 astronomical units from the Sun and the spacecraft is expected to rendezvous with the body in the mid-2030s. The Tianwen-2 spacecraft will conduct remote sensing of the comet to characterize its orbit, shape, and rotation, examine its surface composition and volatile elements, and investigate dust emissions and activity mechanisms to understand cometary behavior in the main belt. 

Tianwen-2 carries a suite of scientific instruments to analyze its targets. Multispectral and infrared spectrometers will study surface composition, while high-resolution cameras will map geological features. A radar sounder will probe subsurface structures, and a magnetometer will search for residual magnetic fields. Dust and gas analyzers will examine comet activity, and charged particle detectors will investigate solar wind interactions. The Space Research Institute of the Russian Academy of Sciences is understood to have contributed to the particle detectors. 

Tianwen deep space series

The Tianwen-2 mission is part of China’s expanding deep space ambitions. it follows the Tianwen-1 Mars orbiter and landing mission launched in 2020. The Zhurong rover successfully landed on the Red Planet in 2021. Tianwen-3 will be a Mars sample return mission and will launch around late 2028 or 2030. 

Tianwen-4 will launch around 2030. It will include a solar-powered Jupiter orbiter which will observe the system and then enter orbit around the moon Callisto. A smaller, radioisotope-powered spacecraft to make a flyby of Uranus.

Chinese researchers last year called for a focus on asteroid sample return missions, citing untapped potential for groundbreaking discoveries and technological innovation

Quelle: SN