5 minute read•Updated 1:48 PM EDT, Fri April 18, 2025
A team of Chinese space engineers has revealed the behind-the-scenes struggles and rapid-response ingenuity that saved two lunar satellites stranded in Earth orbit after a launch anomaly, transforming a near-total loss into a landmark mission for deep space operations and intersatellite communications.
The DRO-A and DRO-B satellites; each part of an ambitious mission to test long-distance communication networks and demonstrate the utility of distant retrograde orbits (DRO) around the Moon, were launched together on March 13, 2024, aboard a Long March 2C rocket from the Xichang Satellite Launch Center.
Their destination: a high, stable lunar orbit where spacecraft circle the Moon in the opposite direction of its orbit around Earth, ideal for long-duration missions. However, the mission nearly failed before it began.
A Spin, a Shortfall, and a Race Against Time
A malfunction in the Yuanzheng-1S upper stage left the satellites in a highly elliptical Earth orbit, far short of the intended trans-lunar trajectory. The satellites’ apogee reached just 134,000 kilometers, well below the required 400,000 kilometers to achieve DRO.
Worse, the satellites were spinning uncontrollably at a rate of one full rotation every 1.8 seconds, fast enough to risk structural damage and prevent stable communication with ground control.
“The situation was extremely dangerous,...It wasn't just about the orbit anymore. We had to stop the spin, regain control, and then try to get them to the Moon, with very limited fuel.” - China Researcher
The DRO-B satellite's attitude control system was quickly activated. In a carefully executed 20-minute procedure, the team was able to slow and stop the spin. Yet problems continued. Telemetry showed irregularities with the solar panels on both satellites, damage that later turned out to be severe.
Rapid Response, Limited Resources
A team composed of experts from the Innovation Academy for Microsatellites (IAMCAS) and the Technology and Engineering Center for Space Utilization (CSU), both under the Chinese Academy of Sciences (CAS), convened immediately. Working around the clock, they developed a 40-hour rescue strategy that required flawless execution.
“We had just days to make the first burn...If we missed the opportunity, the window to reach DRO would close, and the mission would be lost.” - CSU Mission Planner
On March 18, just five days after launch, a 1,200-second engine burn was performed to raise the apogee from 134,000 km to 240,000 km, bringing the satellites back on a viable path for lunar capture.
Over the next four months, the DRO-A and DRO-B spacecraft executed four additional complex orbital maneuvers, including Earth-Moon gravity assists and fine-tuned trajectory corrections. Each burn required precise timing and calculation, balancing the satellites’ fragile state and dwindling fuel reserves.
By July 15, 2024, the satellites had traveled approximately 8.5 million kilometers, reaching distances more than one million kilometers from Earth. This enabled a low-energy capture into DRO using gravitational dynamics, akin to those used in past missions like NASA’s ARTEMIS and China’s Chang’e-2.
Bent Panels, Broken Wings; But It Worked
The final triumph came on August 28, when DRO-A and DRO-B successfully separated from each other and completed mutual imaging.
The images revealed that the DRO-A satellite’s solar panels were bent almost 90 degrees; survivable, but heavily deformed, while DRO-B’s panels resembled “broken wings,” as described by mission engineers.
Despite their condition, the satellites successfully established K-band microwave intersatellite links with the previously launched DRO-L satellite in low Earth orbit. This created a three-node communication network spanning Earth and lunar space—a breakthrough in long-distance space communication.
“For the first time internationally, we have achieved the ability to use satellites to track other satellites, instead of relying on ground stations...This essentially turns a ground station into a satellite itself, ushering in new capabilities for future Earth-Moon operations.” - Wang Wenbin, CSU Researcher
Scientific and Strategic Significance
Beyond its role as a technology demonstrator, the DRO-A satellite carries an all-sky gamma-ray detector, similar to the one flown on China’s 2020 GECAM mission. Scientists aim to use the spacecraft to monitor gamma-ray bursts and support astrophysical research from a unique orbital vantage point.
The mission’s long-term goal is to use DRO as a platform for fundamental science, including experiments in quantum mechanics, atomic physics, and gravitational physics—taking advantage of the orbit’s long-term dynamical stability.
A Rescue Mission Turned Historic
The recovery and success of DRO-A and DRO-B is being hailed as a milestone for Chinese spaceflight and a powerful demonstration of mission resilience and innovation under pressure. What began as a failure has now become a case study in how deep space missions might survive and thrive after unexpected setbacks.
As space agencies around the world prepare for more complex operations across the Earth-Moon system, the lessons learned from this mission may shape the next generation of autonomous navigation, satellite networking, and lunar infrastructure.
