Dense GNSS Observations of a Candidate Recovery-Related Secondary Traveling Ionospheric Disturbance Following the Zhuque-3 Reusable Rocket Flight

Reusable launch vehicles introduce new anthropogenic sources for atmosphere-ionosphere coupling, but ionospheric signatures associated with recovery operations remain poorly constrained. We examine the Zhuque-3 reusable flight test on 3 December 2025 and the Long March 12A comparison launch on 23 December 2025 using dense ground-based GNSS observations over mainland China, multi-constellation total electron content (TEC), fixed ionospheric pierce points from BeiDou GEO satellites, and both 1 Hz and 30 s data. Both launches produced trajectory-aligned TEC depletion and an initial traveling ionospheric disturbance (TID), indicating a repeatable launch-phase response. In the Zhuque-3 case, localized depletion also coincided with short-lived Precise Point Positioning fluctuations along affected links. A distinct later wave packet was observed only after Zhuque-3. This packet appeared after the primary response had decayed, had a slower along-track apparent speed of about 1.05 km s-1, and was visible in 1 Hz snapshots. Its timing relative to publicly reported terminal-recovery milestones and order-of-magnitude acoustic travel-time estimates are consistent with upward coupling from a low-altitude source during the final recovery phase. Because direct measurements of the terminal source and full propagation path are unavailable, we interpret this feature as a well-observed candidate recovery-related secondary TID rather than a uniquely proven recovery signature. The results show that reusable-rocket ionospheric effects may extend beyond ascent and motivate targeted recovery-phase monitoring with dense GNSS and complementary atmospheric observations.