The North Korean satellite Malligyong-1 manoeuvered again, and this time it is different

click diagram to enlarge

In two contributions to The Space Review (part 1 here and part 2 here) for the first instance, as well as two follow-up blog posts for later manoeuvers (here, and here), I analyzed three periodic orbit raising manoeuvers by the North Korean military reconnaissance satellite Malligyong-1 (2023-179A) done in February, June and September 2024. They followed a similar pattern: an orbit raise (orbit maintenance manoeuver) in five daily increments, all taking place on late evening passes (13 - 14h UTC = 22 - 23h local time) passes over North Korea.

Now Malligyong-1 has manoeuvered for a fourth time. And while there are some similarities, this time the followed pattern was different.

The orbit raising manoeuver was done between 2025 January 16 and 18, a month later than I had anticipated. However, as can be seen in the diagram above, it was this time done in three daily increments, not five as was the case in previous orbit raising events. 

Compared to the previous orbit raises, the raise during each daily increment was larger, some 2.5 km per increment rather than 1.2 km as in the previous cases, for a total orbital altitude raise of about 7.5 km, which is also somewhat larger than the previous orbit raises (which was 4 km in February 2024 and 6 km in June and September 2024). As during the previous orbital altitude maintenance raises, it brought back the orbital altitude to the initial value from November 2023, when the satellite was launched. See the diagrams below:

click diagram to enlarge

click diagram to enlarge

The three sequential manoeuvers between January 16 and 18 raised both apogee and perigee. The daily rate of RAAN precession is still very close to the ideal sun-synchronous value.

click diagram to enlarge

As was the case for all previous orbit raises, the times I reconstruct for the three incremental orbit raises correspond to the orbital plane of Malligyong-1 passing over or near North Korea (for the method used, see here);

#   DATE       UTC    LAT     LON      ORBITS USED FOR ANALYSIS          RAISE
M1  16-01-2025 13:14  28.6 N  53.4 W   25016.48110101  25017.33556354    2.50 km
M2  17-01-2025 12:52  19.4 N  46.3 W   25017.33556354  25018.12465384    2.51 km
M3  18-01-2025 12:33  20.5 N  41.7 W   25018.45348685  25019.24307946    2.52 km

However, there is a clear difference: all nominal positions do not plot near North Korea this time, but over the mid-Atlantic. Nominal manoeuver times were about half an hour before passing over/near North Korea.

The map below plots the nominal manoeuver positions I reconstruct, as well as a part of the ground trajectory from 10 minutes before to ten minutes after the nominal reconstructed manoeuver time.

click map to enlarge

The red circle in the map is the area where the satellite would be above the horizon as seen from Pyongyang. Clearly - and unlike previous occasions - the manoeuver points do not coincide with this area, although the satellite would pass through the area about 30 minutes after the reconstructed manoeuver moments (for one of the manoeuver moments, I depicted a longer part of the ground trajectory as well with markers each 5 minutes of flight time).

The manoeuvers not conciding with the satellite being over the horizon as seen from the Pyongyang General Satellite Control Center (PGSC), is something new and intriguing. The nominal manoeuver points being over the mid-Atlantic is interesting. 

So how where these manoeuvers initiated? Assuming my reconstruction of the manoeuver points is correct, here are three options, all having their own implications:

(1) use of a pre-programmed, automated orbit raising burn;

(2) an orbit raising burn command sent through a (Russian? Chinese?) relay satellite in GEO;

(3) an orbit raising burn command sent from a groundstation or ship near/around the mid-Atlantic.

The white area depicted in the map is from where a command from a ground station or ship should have been sent in the case of option (3), possibly a location in Brazil or the mid-Atlantic. 

It might be interesting if someone better versed in that than me, could check the presence of North Korean vessels (and Russian and Chinese space tracking vessels) in the mid-Atlantic between January 16 and 18, 2025.

All three nominal positions correspond to a manoeuver just after passing through the Ascending Node, which is often a standard practise with orbit raising manoeuvers when smaller or larger alterations to the orbital inclination are required. However, no such alterations to the orbital inclination are apparent:

click diagram to enlarge

This was the fourth orbit rasing manoeuver episode since Malligyong-1 was launched on 21 November 2023. Here are they all in a table:

#  period           incr    raise    before  after    interval
1  2024 19-23 Feb    5x     4.0 km   498 km  502 km   90  days
2  2024 03-07 Jun    5x     5.7 km   497 km  503 km   105 days
3  2024 06-10 Sep    5x     5.9 km   498 km  504 km   95  days
4  2025 16-18 Jan    3x     7.5 km   496 km  504 km   132 days

A next raise might occur in the period April to June 2025. It will be interesting to see where those manoeuver locations will end up geographically and whether at some point the orbital inclination is adjusted or not.

Possible Space Debris impact in Kenia: a piece of the Ariane SYLDA 2008-034C? [updated]

the metal ring found near Mukuku in Kenia. Image: Kenia Space Agency

the metal ring found near Mukuku in Kenia. Image: Kenia Space Agency

the metal ring found near Mukuku in Kenia. Image: Kenia Space Agency

 

On 30 December 2024, reportedly near 12:00 UTC, an odd object is believed to have fallen from the sky near the village of Mukuku in Kenia (approximately 1.58 S, 37.61 E, some 100 km from the Kenian capital Nairobi). It is metal ring of about 2.5 meter in size and reportedly 500 kg mass, although that mass could be an estimate only.

The Kenya Space Agency is investigating, believing it to be Space Debris. Apart from the metal ring in the pictures, other fragments looking consistent with space debris, for example what looks like carbon wrap and isolation foil, were found several kilometers away from it (see video below):

 

It is still not entirely clear if the object is space debris (although it looks likely), and if so, which object from what launch. There are two reentry candidates for this date, only one of which looks viable as a candidate (see also Jonathan McDowell's summary here).

That viable candidate is object 33155 (2008-034C), an Ariane SYLDA adapter from flight V184, the launch of ProtoStar 1 and BADR 6 to geosynchonous orbit on 7 July 2008. This SYLDA adapter was left in a 1.6 degree inclined GTO following the launch and had its reentry on or near December 30. 

As I will investigate below, using a reentry simulation, both the location where the ring was found and the reported fall time are realistic for it to be this object.

CSpOC, the US military tracking network, last recorded 2008-034C in a 1923 x 146 km orbit on December 23, i.e. a week before the Kenia impact. As this is a very low inclination orbit (1.56 degrees), it belongs to a class of objects that is ill-tracked due to a lack of tracking stations close to the equator. This explains the 1-week gap between the last available orbit and the reentry.

As a note: what is a SYLDA? A SYLDA ("SYstème de Lancement Double Ariane") is a kind of hollow shell put over the first payload, in order that a second payload can be mounted above it.The conical upper part of the SYLDA has a smallest diameter near 2.6 meter, i.e. similar to the size of the ring found in Kenia, which then could be an upper Payload Adapter Fitting (PAF).

A SYLDA (black) as part of a stage, satellite and fairing stack (image: ESA)

An Ariane SYLDA (image: ESA)

CSpOC issued a reentry TIP for this SYLDA for 30 December 2024, 21:38 UTC +- 59 minutes. That is the date of the Kenia event, but not the correct time, as the Kenia event reportedly happened near 12:00 UTC, nine hours earlier. However, the quoted uncertainty of 59 minutes from this TIP is not realistic, if based on the last available orbit (a week old at the time!). A more realistic uncertainty estimate would be +- 1.5 days. 

Ignoring the CSpOC TIP time, I did an independent impact prediction, using the development version of the open source TU Delft Astrodynamics Toolbox (TUDAT).

I used the last available orbit (epoch 24358.42010446) and the nrlmsise00 model atmosphere to run a reentry prediction, using a trial-and-error approach to see whether I could tinker with the drag area such that it would reenter near 1.58 S, 37.61 E near 12:00 UTC on December 30. 

From @DutchSpace on twitter, who is very knowledgeable on Ariane hardware, I got a mass of 505 kg for the SYLDA in question. The dimensions for the SYLDA on flight V184 should have been about 4.5 x 6.4 meter (there are different versions of SYLDA with different mass and sizes).

After some trial-and-error, I can make the object reenter at 1.57 S, 37.61 E  on 30 December 2024 at 11:49 UTC, close to the reported location and time, if I use an average drag area of ~18.24 m². That is a value which is about 63% of the maximum drag area of this SYLDA (roughly 28.8 m²). This is a reasonable value: during earlier reentry analysis for elongated objects like rocket stages (or in this case, a hollow elongated adapter), I found that a drag area of about 60% - 62% of the maximum area is usually a good approximation to account for the variability in drag due to tumbling .

Below is what the approach trajectory from this simulation would be:

click map to enlarge

While my TUDAT simulation does not prove that the object is debris from 2008-034C (SYLDA), it does show that it is feasible for the reported time and location.

How about that 'other' candidate? That was an Atlas Centaur booster, 2004-034B, for which CSpOC gives a TIP of 30 December 2024 21:30 +- 1 m UTC. However, the orbital plane of this candidate did not pass over Kenia at the reported time (12:00 UTC), and moreover, this object was still detected on-orbit several hours after the reported time of the Kenia event (see also Jonathan McDowell's analysis here): the last reported orbit is for epoch 30 December 2024 15:50 UTC (but it is always possible that a part came off earlier). For these reasons, it is not that likely that the Kenia event was due to a part of this object.

@DutchSpace on twitter, who as mentioned is very knowledgeable on Ariane hardware, so far has trouble positively identifying the ring as a SYLDA part (and that worries me). If the reported mass of 500 kg is correct, that is too heavy for it to be part of this SYLDA too. I have some suspicion however that the reported mass is an overestimate.

For now the verdict is: possibly the reentry of parts of the Ariane SYLDA 2008-034C, but not proven beyond doubt yet.

Here is the final output [revised after running both a TUDAT and TUDAT script update] of my TUDAT reentry model (I had it stop at 50 km altitude, as at that altitude the object should have completely fragmented and decelerated, with fragments falling down basically vertically):

mass: 505 kg
drag area: 18.236375 m^2
altitude limit: 50000.0 meter

propagation start: 2024-12-23 10:04:57.030000 UTC
propagation end:   2024-12-30 11:49:25.029545 UTC
final altitude:    49.879

reentry after 7.072 days

REENTRY AT:
2024-12-30 11:49:25.029545 UTC
lat: -1.57
lon: 37.61

Values in the last three lines are nominal only, the error margins over a 7-day integration period are large. Also ignore the superfluous digits. As a reminder: I tinkered with the drag area untill I got a value that made it reenter as close to 1.58 S, 37.61 E and 12:00 UTC as possible, and the above output gives the relevent drag area and the resulting modelled reentry time and location.

The TUDAT script used can be downloaded here (note: you have to use this script with the 'development version' of TUDAT, as the current non-development release of TUDAT has a bug where the epoch of a TLE is incorrectly read). The development version of TUDAT and installation instructions can be found here.

UPDATE 9 Jan 2025:

In a statement to Gaël Lombart of Le Parisien, Arianespace engineers have cast doubt on the identification of the crashed object as a SYLDA part, indicating that the size of the ring does not fit and stating that "this part does not belong to an element of a European launcher operated by Arianespace". So the mystery remains as to what this object's origin is.