The possible reentry in Kenya on 2024 Dec 30

(Source: AirLive, wire services)

It was suggested that the ring is space debris, but the evidence is marginal. The most likely space related possibility is the reentry of the SYLDA adapter from the Ariane V184 flight, object 33155. I originally discounted this identification because Space Force reported a much later reentry time, but now I realize that their reentry estimate is an unreliable extrapolation.

Nevertheless I am not fully convinced that the ring is space debris at all.

Here are the cases I considered.

1. Reentry of Ariane 5 Sylda double payload adapter from launcher L541, flight V184(object 33155). Maybe.
   • Rocket Ariane 5 L541 launched Protostar 1 and Badr 6 on 2008 Jul 7. The upper stage is 5.5m in diameter, so it seems too large. However the upper payload adapter ring of the Sylda adapter is about the correct 2.5m. diameter (but I could be wrong there).
   • Space Force reports reentry occurred on Dec 30, sometime between 2038 and 2238 UTC, well after the Kenya report.
   • However there were no orbit data reported after Dec 23. The orbit on that data was elliptical, around 146 x 1923 km. Such orbits have signficant uncertainty near reentry.

     Furthermore the Ariane V184 flight placed the SYLDA in a very low inclination orbit of i= 2.0 deg. Space Force ability to track objects at such very low inclinations is poor once the objects reach a low altitude orbit, which explains the lack of tracking in the final week.

     This means we can't really be confident about when and where it reentered, especially if Space Force's estimate is really just an extrapolation of data from a week previously.

   • The orbit was equatorial and it did pass over Nairobi at 1118 UTC based on the SGP4 extrapolation of the Dec 23 orbit data (again, unreliable). Makueni County seems to be a bit south of the southernmost extent of the object's orbit but the reports on the location are not really precise - a good latitude and longitude would be nice.
   • But the Sylda isn't the right mass, it's too light. Total Sylda is 440 kg, the ring is probably 50 kg at most. Maybe the 500 kg reported mass of the debris is incorrect.

     

2. Reentry of US rocket stage Centaur AC-167 (28385). Maybe.
   • AC-167 was launched on 2004 Aug 31 by Atlas IIAS from Canaverl, carrying a secret NRO satellite.
   • Reentry was reported by Space Force to have happened at 2130 UTC on Dec 30, over 108E 55N, inconsistent in both time and space with the Kenya report. Space Force continued issuing new orbital data at around 1500 UTC, three hours after the Kenya event.
   • But perhaps the Space Force data is incorrect, or a piece came off a bit earlier. In fact, object 28385 passed directly over Makueni County at 0711 UTC (10:11 am Kenya time), about 5 hours before the reported event.
   • The mass of Centaur is also too low to match the reports

     

   • The Centaur stage is 3.1 metres in diameter. But the forward adapter has a conical section and maybe it has a smaller diameter ring like this.
3. Launch of the ISRO SPADEX PSLV mission from India. No, because
   • launch was at 1630 UTC, after the cited timeframe.
   • All suborbital parts of the launch fell in the Bay of Bengal or (in the case of the third stage) southwest of Australia. See plot:

     

   • All expected orbital components (SPADEX A, SPADEX B and POEM 4) are currently being tracked in orbit by Space Force, so did not unexpectedly reenter.
4. Starlink 1538. No - wrong time and place.
   • Starlink 1538 (object 46071) was launched on 2020 Aug 7 and was retired from the constellation on 2024 Nov 5.
   • According to Space Force, it reentered on 2024 Dec 30 at 1958 UTC over 2 E 0 S (Gulf of Guinea).
   • Orbits earlier that day passed over Somalia and Zambia but not over Kenya.

     

5. Starlink 2115 No - wrong time and place.
   • Starlink 2115 (object 47394) was launched on 2021 Jan 20 and was retired from the constellation on 2024 Nov 5.
   • According to Space Force, it reentered on 2024 Dec 30 at 2320 UTC over 97E 39N (Northern China, near the Jiuquan spaceport).

     

6. Starlink 2351. No - wrong time and place.
   • Starlink 2351 (object 47891) was launched on 2021 Mar 14 and was retired from the constellation on 2024 Sep 28.
   • According to Space Force, it reentered on 2024 Dec 30 at 1757 UTC over 83E 48N (Central Asia)

     

7. Starlink 4785. No - wrong time and place.
   • Starlink 4785 (object 53865) was launched on 2022 Sep 19 and was retired from the constellation on 2024 Nov 8.
   • According to Space Force, it reentered on 2024 Dec 30 between 0201 and 0225 UTC over the Pacific.
   • Orbits later that day would have passed over other parts of Africa, but not over southern Kenya.