DRO A, B

DRO A [CCTV]

DRO B [CCTV]

DRO A and B (Distant Retrograde Orbit) are lunar test satellites designed by the Microsatellite Innovation Institute of the Chinese Academy of Sciences (CAS) to demonstrate relative navigation in cislunar space together with their low earth orbit counterpart DRO L.

The DRO project will demonstrate a single-beam differential relative navigation method to solve the relative navigation requirements of Distant Retrograde Orbit (DRO) satellite formation in cislunar space. The formation of the DRO A and B satellites can be covered by a beam of measurement sent by a Low Earth Orbit (LEO) satellite (DRO L), thus establishing two Satellite-to-Satellite Tracking (SST) links with the LEO satellite at the same time. Then differential measurement data can be obtained by these two SST links. This method can get relative states of the DRO satellite information by combining the differential measurement data and three-body orbital dynamics model.

Additionally DRO A carries a Gamma-ray Transient Monitor.

The pair was launched in March 2024 on a CZ-2C (3) YZ-1S booster from Xichang, but due to an upper stage failure, they remained attached to the upper stage in a lower than planned orbit. The satellites were able to seperate from the upperstage and raise the apogee by themselves to enter distant retrograde lunar orbits to fullfil their mission. In March 2025, DRO B has been moved from DRO to a resonant earth orbit for furter experiments.