I used our TU Delft Astrodynamics Toolkit (Tudat) to explore this idea further, mostly by trial-and-error with various assumed masses and break-up altitudes. I so far have trouble getting results with breakup during or just before the 12:39 UTC first TIP. It requires significant masses separating well before the TIP time, and then the modelled reentry of the R/B no longer fits well with the TIP. However: I am able to reproduce the two TIP times and locations by having a surprisingly small solid object separate at the *PREVIOUS* perigee pass, around 11:24 UTC (so 1h 15m before the first of the two TIP moments). Assuming a solid steel sphere, a 7.9 kg (12.4 cm diameter) object separating from the R/B at the previous perigee around 11:24 UTC at an altitude of about 109.5 km, does indeed survive the next perigee where the R/B reenters at 12:39 UTC (first TIP), and reenters around 13:43 UTC near 5 S, 62 E, values close to the second TIP. - Marco Op 31-1-2026 om 19:25 schreef Marco Langbroek via Seesat-l: >> The ZQ-3 RB reentry was from a somewhat eccentric orbit (more so than your >> average reentry. The last available orbit was 211 x 102 km. >> >> The 12:39 UTC first "reentry" point could be where the R/B started to ablate >> and fragment near perigee. One relatively massive fragment however might have >> survived perigee and finally reentered half an orbital revolution later at >> 13:43 UTC. >> >> I wonder whether that fragment was the dummy payload, still attached to the >> upper stage, that might have come loose during the first "reentry" moment and >> survived, for example because it was a massive dummy mass with relatively >> large weight to size, while the rest of the R/B (the R/B proper) reentered at >> the 12:30 first reentry point. ------ Dr Marco Langbroek Lecturer in optical Space Situational Awareness (SSA) TU Delft, Faculty of Aerospace Engineering section Astrodynamics and Space Missions ------ _______________________________________________ Seesat-l mailing list https://lists.seesatmail.org/mailman/listinfo/seesat-lReceived on Sun Feb 01 2026 - 09:56:17 UTC
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