China Expands Solar Exploration with Tianwen-2 Mission

Mission Overview

On May 28, 2025, at 17:31 UTC, the China National Space Administration successfully launched the Tianwen-2 spacecraft atop a Long March 3B carrier rocket from the Xichang Satellite Launch Center. With a launch mass of 2.1 metric tons, Tianwen-2 initiates a multi-target exploration of the inner and outer Solar System, building on the success of Tianwen-1’s Mars landing in 2021.

Trajectory and Timeline

The mission profile includes a 2.5-year roundtrip to near-Earth asteroid 469219 Kamoʻoalewa, arriving in July 2026, followed by sample-return to Earth in late 2027. After Earth reentry, the spacecraft will adjust its trajectory for a rendezvous with active asteroid 311P/PanSTARRS in the mid-2030s. Primary maneuvers use a hypergolic upper stage with N2O4/UDMH propellants delivering a total delta-v of ~1.2 km/s.

Payload and Sampling Systems

Tianwen-2 carries 11 scientific instruments, including:

• A high-resolution multispectral camera with 0.5 m ground resolution
• Ground-penetrating radar operating at 5 MHz bandwidth
• Laser altimeter and X-ray spectrometer for elemental mapping

The spacecraft’s sampling suite features three acquisition methods:

• Robotic arm with interchangeable end effectors for scooping and coring
• Touch-and-go nitrogen gas blow-down system to fluidize and collect regolith
• Anchor-and-attach drill legs capable of penetrating up to 10 cm into bedrock

A return container sized for ~300 g of material is designed to deliver at least 100 g of pristine samples to terrestrial laboratories.

Technical Overview of Tianwen-2 Systems

Structure and Power: Based on the DFH-4 bus, the 1.5 × 1.5 × 2.2 m chassis supports two 2.5 m diameter solar arrays generating 4 kW at 1 AU, backed by a 100 Ah lithium-ion battery for eclipse operations.

Propulsion and Attitude Control: Four 500 N main thrusters and twelve 10 N RCS thrusters handle deep-space maneuvers. Navigation relies on star trackers and a fiber optic gyro delivering 0.01° pointing accuracy, with autonomous guidance software for proximity operations.

Communications: A 1.2 m X-band high-gain antenna supports downlink at 150 kbps from 1 AU, with low-gain omnidirectional antennas for telemetry during close-approach sequences.

Risk Mitigation and Mission Architecture

Operating around a 60 m diameter body spinning once every 28 minutes with microgravity (~0.2 mm/s²) demands robust safeguards:

1. Autonomous collision avoidance leveraging LIDAR terrain mapping and real-time hazard detection
2. Redundant avionics with triple modular redundancy in flight computers
3. Extensive Monte Carlo simulations of sampling arm dynamics under variable regolith cohesion

“Our simulations indicate a 95 percent probability of successful sample acquisition using the touch-and-go system, even under worst-case surface conditions,” says Dr. Li Wei, lead engineer at the Chinese Academy of Sciences.

Comparative Analysis with Global Missions

Tianwen-2 integrates capabilities achieved separately by other agencies:

• Japan’s Hayabusa2 returned 5 g from Ryugu after a 6-year mission.
• NASA’s OSIRIS-REx delivered 60 g from Bennu following a 7-year cruise.
• ESA’s Rosetta orbited Comet 67P for two years without sample return.

By combining asteroid sampling and a main-belt comet flyby, Tianwen-2 showcases an optimized mission architecture leveraging China’s heavy-lift and precision navigation technologies.

Deep Dive: Scientific Objectives and Expected Insights

Targeting Kamoʻoalewa as a hypothesized lunar ejecta fragment, Tianwen-2 will analyze:

• Oxygen isotope ratios to confirm lunar provenance
• Mineralogical composition via onboard X-ray diffraction and synchrotron comparisons
• Space weathering effects on micrometer-scale grains

These investigations aim to refine models of lunar far-side evolution and asymmetry, shedding light on early Solar System dynamics.

Future Programmatic Outlook

Post-return in 2027, the spacecraft will head for active asteroid 311P/PanSTARRS, marking the first close-up study of a main-belt comet. This mission aligns with China’s broader Tianwen roadmap:

1. Tianwen-3: Mars sample return, launching in 2028
2. Tianwen-4: Jupiter system orbiter around Callisto, targeted for 2029
3. Tianwen-5: Venus atmospheric sampling in the 2030s

While NASA and ESA advance separate Mars Sample Return and outer planet ventures, Tianwen-2’s success will cement China’s role as a leader in multi-target, sample-return exploration.