DRO-A & DRO-B

DRO-A and DRO-B are Chinese Academy of Sciences technology demonstration spacecraft designed to operate in a distant retrograde orbit around the Moon. They test K-band intersatellite communication links at Earth-Moon distances, demonstrate relative navigation techniques for distributed satellite formations in cislunar space, and carry instruments for gamma-ray burst detection.

The Yuanzheng-1S upper stage suffered a premature shutdown after separation - the first failure in the Yuanzheng series - stranding both satellites in a highly elliptical Earth orbit instead of a trans-lunar trajectory. A 123-day rescue effort executed five major propulsive maneuvers alongside lunar and Earth gravity assists, delivering the spacecraft to their intended distant retrograde orbit on 15 July 2024. Both satellites survived solar panel damage sustained during the anomaly and went on to complete their planned mission.