Photometric evolution unveils debris generation process of rocket bodies in geostationary transfer orbits

The study of the long-term evolution of space debris is critically important for understanding debris generation mechanisms and, consequently, for the protection of orbital resources. Here we present a photometric survey of the CZ-3 series rocket bodies in Geostationary Transfer Orbit (GTO), revealing that their standardized brightness exhibits a multi-stage variation pattern over an in-orbit timespan of 41 years. Specifically, the brightness initially decreases, then rapidly increases, followed by a subsequent decrease that eventually stabilizes. Based on our understanding of the CZ-3 rocket bodies' multilayer surface structure, we propose that the shedding of surface materials caused by space weathering is the primary driver behind these brightness variations. A similar evolutionary trend is observed in the Atlas V series rocket bodies. Based on this mechanism, we also explore the potential origins of previously unidentified debris in GTO reported in earlier studies.