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In a groundbreaking achievement for lunar navigation, Chinese scientists have successfully conducted laser ranging to the Tiandu-1 satellite in Earth-moon space during daylight hours, marking a world first that overcomes long-standing technical barriers.
Key Takeaways
- Chinese scientists successfully captured laser return signals from the Tiandu-1 satellite approximately 130,000 km away despite strong daylight interference.
- The achievement marks the world's first daytime satellite laser ranging in Earth-moon space, previously limited to nighttime operations.
- The precision required is comparable to "hitting a single hair from 10,000 meters away" while tracking a fast-moving satellite.
- This breakthrough significantly expands observation windows for collecting orbital data, enhancing navigation capabilities for future lunar missions.
- The Tiandu-1 satellite was launched in March 2024 as part of China's efforts to build an Earth-moon communication and navigation network.
- The technology will support major deep-space exploration projects, including the International Lunar Research Station.
- The research team utilized a newly upgraded near-infrared laser ranging system with a 1.2-meter telescope at Yunnan Observatories.
The Daylight Breakthrough
For decades, laser ranging in Earth-moon space has been restricted to nighttime operations due to overwhelming solar interference that drowns out laser signals during daylight hours. This limitation has significantly constrained observation periods and reduced the frequency of orbital data collection for lunar missions.
In a remarkable technological leap, Chinese scientists successfully conducted a laser ranging experiment with the Tiandu-1 satellite under strong daylight conditions on April 26-27, 2025. The achievement effectively removes a major obstacle in deep-space tracking and navigation.
According to researchers at Yunnan Observatories of the Chinese Academy of Sciences (CAS), the team captured the laser return signal from the retroreflector of the Tiandu-1 satellite using their newly upgraded near-infrared lunar laser ranging system mounted on a 1.2-meter telescope.
The precision required for this feat is extraordinary. China's Deep Space Exploration Laboratory (DSEL) compared the accuracy to aiming at a single hair from 10,000 meters away while performing precise tracking and signal acquisition. Other sources described it as similar to "hitting a single hair from 6.2 miles away," highlighting the remarkable precision achieved.
Technical Challenges Overcome
The primary challenge in daylight laser ranging is the suppression of strong solar background noise. The team had to develop sophisticated filtering and signal processing techniques to detect the extremely faint laser return signal against the overwhelming brightness of daylight.
Li Yuqiang, a researcher at Yunnan Observatories, confirmed that this achievement represents a new technological breakthrough for China in the field of precise deep-space orbit measurement. The success hinged on overcoming the strong solar background noise that typically overwhelms laser signals during the day.
The research consortium behind this achievement brings together expertise from multiple institutions, including China's Deep Space Exploration Lab, Yunnan Observatories, Shanghai Astronomical Observatory, Sun Yat-sen University, the Shanghai Institute of Satellite Engineering, and the Beijing Aerospace Control Center.
The Tiandu Satellite Mission
Tiandu-1 is a communication and navigation technology test satellite launched on March 20, 2024. It was sent into space alongside Tiandu-2 and the Queqiao-2 relay satellite, forming part of China's ambitious plans to establish an Earth-moon communication and navigation network.
After launch, the satellites entered their target circumlunar orbits on March 29 and separated on April 3, according to reports. Since then, they have been conducting a series of technological experiments for lunar communication and navigation.
The Tiandu satellites represent the first spacecraft ever developed by DSEL and are foundational elements of China's upcoming Queqiao relay constellation. This planned network will support future lunar landers, rovers, and even crewed missions expected before 2030.
Implications for Lunar Exploration
The successful daylight laser ranging test significantly expands the observation window for this technology, providing a practical engineering foundation for its widespread application in deep space missions.
By enabling around-the-clock laser ranging, China has effectively removed one of the final blind spots in Earth-Moon tracking. This capability is crucial for autonomous spacecraft operations, high-precision landing guidance, and the real-time coordination of rover fleets on the Moon's surface.
The technology will also play a central role in approach, descent, and landing systems for future missions to the lunar south pole. It will strongly support the validation and implementation of major deep space exploration missions, such as the International Lunar Research Station.
This milestone comes amid a broader wave of advancements in China's lunar program. The country's Chang'e-6 mission recently returned the first-ever samples from the Moon's far side, and the upcoming Chang'e-8 mission (scheduled for 2028) is slated to test small nuclear reactors and other infrastructure to power the International Lunar Research Station.
China's achievement in daylight laser ranging represents a significant advancement in deep-space navigation technology that will enable more continuous and precise operations between Earth and the Moon, accelerating progress toward sustained lunar presence and exploration.
