In a ground-breaking feat, Chinese scientists have broken new ground in satellite laser ranging by firing a laser across more than 80,000 miles and bouncing it off a Moon-orbiting satellite in broad daylight.
Satellite laser ranging, often described as the gold standard for orbit tracking, is a method that involves firing ultra-short laser pulses at satellites equipped with retroreflectors. These pulses bounce back to Earth, allowing researchers to calculate distances with extreme precision, down to the centimeter. While this method is commonplace for satellites in low-Earth orbit, extending it across the vast Earth-Moon gap during daylight has long been a formidable challenge due to interference from solar light.
China’s Deep Space Exploration Laboratory (DSEL) has now overcome this limitation, proving that high-precision laser measurements can be reliably conducted even under daylight conditions. One expert likened the achievement to “aiming at a sub-millimeter target—essentially a single hair—from over 6.2 miles away,” capturing just how meticulous and refined this technology has become.
The successful daylight ranging of the Tiandu-1 satellite means that China can now collect orbital data more frequently and with higher consistency. This is especially important as China builds out its Queqiao satellite constellation, a system designed to provide uninterrupted communication and navigation services for lunar exploration.
Tiandu-1, together with its sister satellite Tiandu-2 and the Queqiao-2 relay satellite, already serves as the structural backbone of China’s Moon-focused endeavors. These spacecraft have returned high-resolution images of the lunar surface and demonstrated robust inter-satellite communication, both key for supporting more complex missions in the near future.
Looking ahead, the China National Space Administration (CNSA) is pressing forward with plans for a crewed Moon landing by 2030. By 2035, it aims to begin construction of the International Lunar Research Station, in collaboration with Russia. In these ventures, laser ranging will be critical not just for orbital calculations, but also for guiding landers, coordinating fleets of robotic rovers, and establishing safe, efficient lunar logistics.
