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.

X-37B Spaceplane OTV 7 to lower orbit by aerobraking

X-37B OTV 7 near apogee  imaged by the author on 3 October 2024. Click to enlarge

It looks like the time on orbit is about to end for mission OTV 7 of the enigmatic US Space Force X-37B spaceplane (2023-210A). Launched on 29 December 2023, it went into an unusual Highly Elliptical Orbit with apogee near 38 600 km and perigee near 300 km and an orbital inclination of 59 degrees (see various earlier blogposts).

On October 10, the US Space Force announced that OTV 7 "will begin executing a series of novel maneuvers, called aerobraking, to change its orbit around Earth and safely dispose of its service module components in accordance with recognized standards for space debris mitigation"

I already wrote earlier, e.g. in this blogpost from February, that the mission likely would end by using aerobraking in perigee to lower apogee, circularize in a Low Earth Orbit, and then land. 

Aerobraking is a technique where, by a manoeuver in apogee, the perigee altitude of the orbit is lowered such that it is in the top of the atmosphere: not low enough to make it reenter, but enough to significantly slow it down. When the spacecraft goes through perigee in that situation, it experiences enhanced drag, that will result in drastically lowering the apogee of the orbit, certainly after a few of such perigee passages. 

This will bring the orbit down and eventually change the Highly Elliptical Orbit character into a Low Earth Orbit. Orbital velocity near perigee (over 10 km/s while in a Highly Elliptical orbit with apogee near 39 000 km) will be drastically reduced (to 6.8 km/s) by this, allowing the vehicle to reenter the atmosphere and land without experiencing too excessive forces during reentry.

It looks like the process of lowering perigee might already have started around October 4, when for the first time perigee (while earlier just above 300 km) seems to drop below 300 km:

OTV 7 apogee and perigee altitudes over time. NOTE: logarithmic Y-axis! Click to enlarge

This is difficult to say for certain, as frequent larger and smaller manoeuvers by OTV 7 (it seems to have manoeuvered daily, as it never was on the ephemerids during a next observation) combined with a sketchy observational coverage (most of the observations from the last two months have been done by me, with some by Tomi Simola), means that orbit determinations are not always that easy and it is not clear how real the minor variations in perigee altitude from orbit determination to orbit determination are.

The wording of the US Space Force news item is such, that it seems to suggest that after apogee lowering and orbit circularization through aerobraking, OTV 7 might for a while continue its mission in a lower (Low Earth) orbit, as they write:

"Once the aerobrake maneuver is complete, the X-37B will resume its test and experimentation objectives until they are accomplished, at which time the vehicle will de-orbit and execute a safe return as it has during its six previous missions".

So rather than land directly after the aerobraking sequence is finished, it might stay on orbit for days, weeks or months, in an orbit that is more like those of previous X-37B missions.

Over the past two months, perigee has been kept on the equator (argument of perigee kept near 180 degrees). That is a situation where during a perigee pass, there is the possibility to change the orbital inclination. So it is possible that near the end of the aerobraking sequence, the orbital inclination (currently 59 degrees) will be changed to a lower value, e.g. around 40 degrees as with previous X-37B missions in LEO.

As an interesting aside, the US Space Force bulltein also mentions that mission OTV 7 in its unusual HEO orbit "has conducted radiation effect experiments and has been testing Space Domain Awareness technologies in a Highly Elliptical Orbit".

X-37B spaceplane. Image: US Space Force

A Chinese ICBM test launch at full range, into the central Pacific, on September 25

click image to enlarge

click image to enlarge

In a surprise move, China conducted a (for them) unusual ICBM test launch on September 25, 2024. They launched an ICBM at full range, targetting an RV splash-down area in the central Pacific.

According to China the missile, with a "dummy warhead", was launched at 00:44 UTC (Sept 25) "to the high seas in the Pacific Ocean". Several countries (including the US, Japan) were reportedly informed before the test, and Navigational Warnings were issued for the RV impact area and missile stage splashdown areas two days before the test.

The Navigational Warnings and NOTAM's indicate that the missile was launched from the northern part of Hainan Island, with RV splashdown near 10.4 S, 146.5 W near French Polynesia, some 700 km west of Nuku Hiva and 875 km northeast of Bora Bora. The indicated range flown by the ICBM was about 11 700 km.

I have plotted the relevant hazard areas from the Navigational Warnings (HYDROPAC 3118/24, HYDROPAC 3121/24) and a NOTAM (A3054/24) with a matching reconstructed ballistic flight path on the map below, while the two illustrations in top of this post show the approximate trajectory in 3D (assuming apogee at 1200 km and launch on the Hainan coast).

click map to enlarge

Given the launch from Hainan, it was likely a road-mobile ICBM (perhaps a DF-31 or DF-41 [UPDATE: it was a road-mobile DF-31A or AG, see update at bottom of post]) launched from a TEL. The exact launch location is still unclear at the moment. The location of the hazard areas (especially that from NOTAM A3054/24) seem to rule out launch from the Wenchang Space Launch Complex, as they rather point to slightly more north on Hainan.

China usually test launches its ICBM's over land, on lofted trajectories (e.g. see this 2019 blog post). The last time they launched one at full range on a non-lofted trajectory into the Pacific was 44 years ago, in 1980. So this launch is far from a standard test.

In addition to being an ICBM non-lofted test, the test could perhaps also have been for the purpose of testing China's TJS/Huoyan early warning satellites in geosynchronous orbit.

Relevant Navigational Warnings and NOTAM:

231141Z SEP 24
HYDROPAC 3118/24(91,93).
PHILIPPINE SEA.
PHILIPPINES.
DNC 23.
1. HAZARDOUS OPERATIONS, SPACE DEBRIS
   242200Z TO 250400Z SEP IN AREAS BOUND BY:
   A. 19-46.00N 118-15.00E, 19-36.00N 119-48.00E,
      18-33.00N 119-41.00E, 18-44.00N 118-08.00E.
   B. 19-06.00N 124-41.00E, 18-57.00N 125-42.00E,
      18-11.00N 125-36.00E, 18-21.00N 124-34.00E.
2. CANCEL THIS MSG 250500Z SEP 24.


231521Z SEP 24
HYDROPAC 3121/24(83).
SOUTH PACIFIC.
DNC 06.
1. HAZARDOUS OPERATIONS, SPACE DEBRIS
   242200Z TO 250400Z SEP IN AREA BOUND BY
   09-37.00S 147-14.00W, 10-18.00S 145-31.00W,
   11-08.00S 145-44.00W, 10-27.00S 147-29.00W.
2. CANCEL THIS MSG 250500Z SEP 24.


A3054/24 NOTAMN
Q) ZGZU/QRDCA/IV/BO/W/000/999/1952N11145E018
A) ZGZU B) 2409250020 C) 2409250230
E) A TEMPORARY DANGER AREA ESTABLISHED BOUNDED BY:
N200247E1113156-N200222E1120118-N194011E1120042-N194142E1113027,BAC
K TO START.
VERTICAL LIMITS:SFC-UNL.
F) SFC G) UNL

 

There are three more NOTAM's that correspond to the areas from the Navigational Warnings. (HT to Cosmic Penguin on Twitter for the NOTAM).

 

UPDATE 26 Sep 2024:

China has published images of the launch. It shows a launch from a TEL, with a missile and TEL consistent with a DF-31A or AG.

Image: PLA

The Russian SIGINT satellite LUCH (OLYMP-K) 2 has moved again

LUCH (OLYMP) 2 position change. Click image to enlarge

 

Luch (OLYMP) 2 (2023-031A), the second Russian OLYMP-K/LUCH 5X SIGINT satellite in geosynchronous orbit, has changed position several times since its launch in 2023. Each time, it was placed near a commercial communications satellite. I have written about it before on this blog (e.g. here), and two (here and here) 2023 Space Review article by Bart Hendrickx provides more background on the OLYMP-K program.

And now LUCH (OLYMP) 2 has moved again. From its previous position stalking THOR 7 (2015-022A) at longitude 0.54 W, where it arrived on July 1 2024, it has now made a small hop to the other side of the THOR + INTELSAT grouplet, to 0.92 W, taking a position inbetween THOR 6 (2009-058B) and INTELSAT 1002 (2004-022A).  

The move started on 16 September 2024 near 22 UTC and was completed on September 18.

LUCH 2 positions over time. Click diagram to enlarge

 

detail of the lastest move (top). Click diagram to enlarge

The photographs in top of this blogpost shows the change in position by LUCH (OLYMP) 2 over the past week: basically moving from one end of the grouplet to the other.

(as soon as the moon is less of a nuisance, I will attempt to get a better picture of LUCH (OLYMP) 2 at its new position, with a larger phase angle).

This is not the first "small hop" of LUCH (OLYMP) 2 to the other side of a visited satellite grouplet. In December 2023, it also made a small hop, from 3.2 E to 2.6 E, moving from EUTELSAT 3B to EUTELSAT KONNECT VHTS.

Meanwhile, it is not the first time either that a LUCH (OLYMP-K) satellite is checking out INTELSAT 1002. The latter has been visited by an earlier LUCH (OLYMP) satellite, LUCH (OLYMP) 1 (2014-058A) twice before.

The relocations of LUCH (OLYMP) 2 so far come at intervals of roughly 3 months.

It is still a bit mysterious why exactly these LUCH (OLYMP) satellites are stalking commercial satellites. The roles of their victims are somewhat diverse, although most of the stalking targets in one way or another have to do with data transmissions and TV broadcasts (but there appear to be no relations to recent Russian satellite TV hacks). They could perhaps be mapping contact networks, tapping data streams, analysing frequency hopping patterns, or even analyse weak energy field transmissions within their target satellites. Or they are just there to feed paranoia and provoke counterspace methods.

The North Korean satellite Malligyong-1 has manoeuvered again

click map to enlarge

At the end of the first week of September, the North Korean military reconnaissance satellite Malligyong-1 (2023-179A) made an orbit raising manoeuver again, as I predicted in June.

The raise can be seen as sudden altitude jumps at the righthand side in the diagrams below, that plot the change in the satelllite's apogee and perigee altitude over time. The first diagram shows Malligyong's orbital evolution since launch in 2023, with three orbit raising events, one in February 2024, one in June 2024 and now one in September 2024 (the gradual sinusoid trends are due to natural orbit decay and periodical evolution of the orbital eccentricity: the sudden stepped "jumps" are manoeuvers). The second diagram is a detail and shows the current September orbit raise, in five distinch daily steps:

click diagram to enlarge

click diagram to enlarge

As was the case for the orbit raising manoeuvers in February and June 2024, the raise was performed in five incremental steps, one per day. The first manoever was on September 6, the last on September 10. It raised the average orbit by 5.9 km, similar to the altitude raise in June, to 504 km (see diagram below), slightly above the initial orbit insertion altitude from the launch in November 2023. While the June manoeuvers raised both perigee (slightly) and apogee, this time only the apogee was raised, from 499 km to 511 km, a raise of 12 km (see diagrams above).

click diagram to enlarge

As a result of the manoeuver, the value for the daily RAAN precession is now slightly under, but still very close to, the ideal sun-synchronous value, with the match improving over time (se diagram above)

From the pre- and post-manoeuver orbital data, I reconstruct these five sequential nominal manoeuver times (for an explanation of how these times were determined, see my earlier analysis of the February manoevres in The Space Review of 8 April 2024):

 

#  DATE         UTC     LAT     LON       ORBITS USED FOR ANALYSIS          RAISE
M1 06 Sep 2024  13:12   36.9 N  137.4 E   24250.58978379  24251.57588172    1.17 km
M2 07 Sep 2024  14:24   48.6 N  122.4 E   24251.57588172  24252.49645891    1.18 km
M3 08 Sep 2024  14:01   60.6 N  133.0 E   24252.49645891  24253.21993764    1.19 km
M4 09 Sep 2024  13:43   55.0 N  134.8 E   24253.54879868  24254.20668986    1.20 km
M5 10 sep 2024  13:32   26.0 N  130.6 E   24254.20668986  24254.93046907    1.19 km

 

These nominal positions correspond to the crosses in the map below, with the lines showing the trajectory from 10 minutes before to 10 minutes after the nominal manoeuver time:

click map to enlarge

As can be seen, and as was the case in February and June, all manoeuver times correspond to passes within direct line-of-sight range of the Pyongyang General Satellite Control Center (PGSC) in North Korea (the red oval in the map is the geographical area where the satellite will be above the horizon as seen from Pyongyang). And as was the case in February and June, all manoevers were done on late evening passes, between roughly 13 -14 UTC (10-11 pm local time in Pyongyang).

The manoeuvers started three days earlier than I had predicted. In June, I had predicted the next manoeuver to start either Sept 9, Sept 16 or Sept 23. That was based on the time between previous manoeuvers, and the fact that these were initiated on Mondays. This time however, the series of manoeuvers started on a Friday.

We can expect the next orbit raising manoeuver to happen mid-December 2024, most likely somewhere around December 13-16, on local late evening passes (13-14 UTC) within direct range of  Pyongyang.

ACS 3 appears to be tumbling or gyrating

 

(this post was lightly editted and extended after initial posting)

In a previous post I reported my first post-sail-deployment observations of NASA's ACS 3 (2024-077B), the Advanced Composite Solar Sail System.

I observed the Solar Sail again in the evening of September 1, 2024, and this time the brightness of the Solar Sail was quite different. As it rose in the south, it became very bright, reaching magnitude 0 (as bright as the brightest stars in the sky). It then faded again, and next displayed a slow brightness variation with multiple bright maxima and very faint minima.

The video above, shot with my WATEC 902H2 Supreme camera and a Samyang 1.2/85 mm lens, shows some of the brightness variation (NOTE: the footage is not a continuous sequence!) with several peaks and valleys.

Below is a fragmentary brightness curve. During minima I lost the satellite a few times, and during maxima it was oversaturated (so the diagram does not capture the peak brightness well). The brightness seems to indicate a slow cycle of around half a minute:

 

click diagram to enlarge

 

The brightness variation could be suggestive of a slow tumble or wobble (a gyration around an axis) that must have been initiated after August 29, when it appeared more steady (apart from a brief bright flare, probably due to a favourable sun-sail-observer geometry). There might be other explanations though (which is why I use the word "appears" and "could").

Interestingly enough, in the orbital data a clear and sudden change can be seen after August 30.4 UTC, when the orbital eccentricity increased, and as a result both apogee and perigee changed (see diagram below). Perhaps that was the moment the tumble or wobble, if it is one, started. It will be interesting to see whether it stabilizes again over the next days.

It is to be expected that once the solar sail is unfurled, the Solar Radiation Pressure acting upon it will cause the orbit to change (that is the whole point of the solar sail experiment). That is likely what we see here. The orbital change started ~0.8 days after sail deployment, so that might perhaps be the moment they reoriented the sail to take advantage of the SRP to change the orbit. The ACS 3 mission blog on August 29 indeed wrote that "during the next few weeks, the team will test the maneuvering capabilities of the sail in space".

click diagram to enlarge

The Advanced Composite Solar Sail System 3 (ACS 3) observed after sail deployment [UPDATED]

ACS 3 on 29 August 2024. Click to enlarge

 

On April 23, 2024, Rocketlabs launched an Electron rocket for NASA carrying ACS 3 (2024-077B) , the Advanced Composite Solar Sail System, into a 994 x 1023 km, 97.4 degree inclined Sun-Synchronous orbit. 

ACS 3 is a 12U cubesat carrying a deployable 9.9 x 9.9 meter solar sail with a total effective surface of 80 m² . The sail is very thin (2.115 micrometer). For more information on the mission  see here on the mission page, and this scientific paper here.

Due to power issues it took a while (over 4 months) before the sail was actually deployed. That happened on August 29 and was completed near 17:33 UTC.

Three hours after the deployment, I observed a pass of the spacecraft over my home in Leiden, the Netherlands, near 20:26 UTC (August 29).

The image above shows the solar sail near peak brightness, ascending over my rooftop near 20:26:42 UTC (August 29). The image was taken with a Canon EOS 80D + Samyang 1.4/35 mm lens at F2.0 and ISO 800 with an exposure time of 5 seconds.

It was not very bright, briefly reaching magnitude +3 (moderate naked eye visibility) but for most of the pass it was much fainter (below naked eye visibility).  Nevertheless, it has become much brighter than before sail deployment,( see below), as was to be expected, by at least 4-5 magnitudes.

The observation was during a west pass in the evening, i.e. not the most favourable illumination angle. It is possible (I haven't had the opportunity to re-observe it yet) that it is brighter during an evening east pass. Given that it is a flat reflective sail, it is also possible that under specific circumstances a narrow strip on Earth might see a much larger brightness. On the other hand, the reflective coating of the sail is pointing towards the sun, away from earth.

I had targetted the object a couple of times earlier over the past few months, before the sail was deployed, using the WATEC 902H2 Supreme and a 1.2/85 mm lens. Most of the passes it was beyond visibility: on two occasions, I had a positive but very faint detection of the 12U cubesat bus plus solar panels. As it orbits at 1000 km altitude, the bus was much less easy to detect that other cubesats that are usually in lower orbits (400-500 km).

Below is a framestack from a positive detection on May 3, 2024 (see also this earlier post), when it was briefly but very faintly seen with a brightness near magnitude +9.5. The very faint trail can be seen in the lower right of the image:

click to enlarge

Over the coming months, the solar sail will be used to manoeuver the spacecraft. They will first raise and then lower the orbit, using the Solar Radiation Pressure (SRP) on the sail as propulsion. They expect to be able to change the semi-major axis this way by up to 1-2 km/day.

I vividly remember observing another experimental solar sail, Nanosail-D in 2011, which was in a lower orbit and quite bright in twilight, with a stroboscopic flash pattern due to tumbling (see amongst other this earlier post from 2011). 

 

UPDATE 2 Sept 2024:

On September 1, I observed the Solar Sail again and this time it was much brighter and showed clear brightness variations perhaps indicating tumbling or a gyration. More in this follow-up post.

More X-37B spaceplane OTV 7 observations

OTV 7 imaged on August 11. Click image to enlarge

In a previous blogpost I wrote about recovering the X-37B Spaceplane OTV 7 (2023-210A) on July 30. I have now observed it a couple of times, at intervals of a few days due to a combion of weather conditions and favourable or less-favourable pass times. Above is an image from August 11. The diagram below shows where it was in its orbital position at that time, coming down from apogee:

click image to enlarge

 

Between mid-March and end-of-July, OTV 7 had brought down its apogee by a few thousand kilometers. Since recovery on July 30, it is continuously making smaller manoeuvers as well (currently, it seems to make small orbit raising manoeuvers adjusting both apogee and perigee). As a result, it is invariably off predictions (usually being a bit 'late') and a small plane scan is necessary to recover it. Having a wide-field instrument (the FOV of the instrument I currently use, an ASI 6200 MM PRO with 1.2/85 mm lens, is 24 x 16 degrees) is useful in this aspect.

The brightness of OTV 7 strongly depends on where it is located in its orbit during observation (as well as, of course, phase angle and condition of the local sky). When it is in or near apogee, it is fainter and the trail is short.

When following the object over (a part of) a pass, the brightness and apparent angular rate of movement (trail length) notably changes. How clearly it can be seen in the imagery is complex interaction of actual brightness, apparent angular movement (when it moves faster, each image pixel is illuminated less), range to the observer and phase angle.

Below are two images from the night of August 14-15, some 3 hours after OTV 7 passed apogee. The second of these images shows OTV 7 not far from M31, the Andromeda galaxy. Even though the two images are not at the same image scale (the one with M31 is reduced in size, to show a wider FOV), the difference in trail length after a mere half an hour can already be seen (both images are 10-second exposures with a ZWO ASI 6200 MM PRO and Samyang 1.2/85 mm lens).

Recovery of the X-37B spaceplane OTV 7

click to enlarge

 

The classified US Space Force X-37B spaceplane OTV 7 (2023-210A) was launched on 29 December 2023, in an unusual Highly Elliptical Orbit. Five weeks after launch, in the first week of February 2024, it was found on-orbit by Tomi Simola from Finland in a 38600 x 300 km, 59.15 degree inclined orbit (see this earlier blogpost). We followed it for a month and then lost it: the last observation was on March 15.

But now it has been recovered! On the night of July 30-31, I was imaging geosynchronous objects when I noted a short trail made by an unidentified interlooper.  Mike McCants identified the UNID as OTV 7.

The image in top of this post (one out of four images spanning half an hour) shows the short faint trail created by OTV 7. The ~9 by 4.5 meters large X-37B spaceplane was near apogee of its orbit at that time, at about 35535 km altitude (and a range of some 38775 km to my observing location). The image is a 10-second exposure with a ZWO ASI 6200 MM PRO and Samyang 1.2/85 mm lens, and shows only a small part of the original image. It was taken from Leiden, the Netherlands.

Weather next initially conspired against me, but last night, August 3-4, I again observed it, some 25 minutes late on the initial elset estimate. This is a small part of one of the images, shsowing the faint trail created by OTV 7:

click image to enlarge

The observing conditions were very dynamic this time: after rainshowers, small but bright, stamp-sized clearings were sometimes present in the clpud cover. I managed to image the object through such gaps in the cloud cover a few times over an half-an-hour-period, 25 minutes late on the preliminary orbit. 

Below is an example of what I am talking about when I say "stamp-sized clearings": this is the last image (reduced in size as the true image is 9576 x 6388 pixels) on which I could find it. All the white is clouds....:

click to enlarge

The new observations constrain the orbit a little bit better: 314 x 35552 km, 59.15 degree inclined. A provisional elset:

OTV 7
1 58666U 23210A   24216.90625742 0.00000000  00000-0  00000+0 0    01
2 58666  59.1511 329.1636 7247171 178.5736 186.3429  2.29027449    03

rms 0.004 deg   from 9 obs, arc July 30.96 - Aug 3.96 UTC

Below is a comparison between the (forward propagated) orbit from March (red), and the current orbit (white). Apogee is some 2300 km lower than it was in March (and this is not due to natural orbital decay, but due to manoeuvering). The orbital plane itself is still similar.

click image to enlarge

The Russian SIGINT satellite LUCH (OLYMP) 2 has arrived at its new destination, next to THOR 7

LUCH (OLYMP) 2 imaged at its new location on July 6. Click image to enlarge

 

In a previous blogpost I signalled that the Russian military SIGINT satellite LUCH (OLYMP) 2 (2023-031A), also known as LUCH-5X, a satellite that stalks other satellites, started another relocation move on July 22, leaving its position near ASTRA 4A at longitude 4.8 E and drifting west at 0.9 degrees per day. 

On July 1, the drift stopped as it arrived at its new target destination at longitude 0.54 W. As expected, it has been placed close to yet another western commercial geosynchronous satellite: the Norwegian satellite THOR 7 (2015-022A).

The image above shows both satellites - plus a couple of other neighbouring ones - as imaged by me from Leiden in the night of July 6/7, when I finally had clear skies again, albeit briefly. The image is a 10-second exposure taken with a ZWO ASI 6200 MM PRO + 1.2/85 mm lens. 

At the moment the image was taken, LUCH (OLYMP) 2 and THOR 7 were some 84 km apart. That distance might diminish further: the Russian satellite is still slowly drifting closer to THOR 7.

This is the sixth relocation of LUCH (OLYMP) 2, and the fifth satellite it visits (see diagram above). I expect that it will stay close to THOR 7 for a few weeks and then move on again, possibly to one of the neighbouring satellites (THOR 5 or 6, or INTELSAT 1002), or to a new location altogether.

I also imaged LUCH (OLYMP) 1 (2014-058A), the predecessor of LUCH (OLYMP) 2 (see image below). It has been parked close to INTELSAT 37E (2017-059A) at longitude 18.1 W since September 2022, following an earlier life of frequent relocations (some 30 relocations between 2014 and 2022):

 

LUCH (OLYMP) 1 near INTELSAT 37E on July 6. Click image to enlarge

More on both LUCH (OLYMP) 1 and 2 and their program backgrounds can be found in this article from 2023 by Bart Hendrickx in The Space Review.

As I wrote in a previous blogpost, what LUCH (OLYMP) 2 and its predecesssor LUCH (OLYMP) 1 are doing so close to commercial satellites is an interesting issue. To name a few possibilities: they might be gathering information to map contact networks; geolocating targets that use the satellites; eavesdropping on data communications; prepare for or actually do jamming or spoofing activities; or checking these satellites for vulnerabilities that might provide a means to disable them, might need come.

LUCH (OLYMP) 2 is on the move again [UPDATED]

Image from June 27, 2024. Click to enlarge

 [ UPDATED on 5 July 2024 ]

The Russian military geosynchronous SIGINT satellite LUCH (OLYMP) 2 (2023-031A) is on the move again. It has left its position at longitude 4.7 E with a manoeuver initiated on 22 June 2024, likely around 11:40 UTC. It is now drifting westwards with a drift rate of approximately 0.9 degrees per day. 

The change in several orbital elements after mid June 22 is well visible in the TLE data:

It will be interesting to see what LUCH (OLYMP) 2's next stalking victim will be.

LUCH (OLYMP) 2, which was launched on 12 March 2023, is building a history of frequent relocations, like its predecessor LUCH (OLYMP) 1 (2014-048A) did. With each relocation, it is placed close to a commercial satellite. Below shows the position it had between April 1 and June 22 close (daily varying between 20-75 km) to ASTRA 4A at 4.7 E, where it arrived on April 2, 2024 (see this earlier blogpost) until it left there on June 22. 

 

 

So far LUCH (OLYMP) 2 has stalked at least four commercial satellites:

ARRIVED      LEFT         LON      NEXT TO
22-05-2023   25-09-2023   9.0 E    EUTELSAT (KA SAT) 9A/EUTELSAT 9B
04-10-2023   04-12-2023   3.2 E    EUTELSAT 3B
05-12-2023   26-03-2024   2.6 E    EUTELSAT KONNECT VHTS
01-04-2024   22-06-2024   4.7 E    ASTRA 4A

Below, the movements since launch in diagram form, showing the longitude of placement The first two placements at 78 E and 58 E were probably check-out placements.

click diagram to enlarge

What LUCH (OLYMP) 2 (and its predecesssor LUCH (OLYMP) 1) is doing so close to commercial satellites is an interesting issue. To name a few possibilities: it might be gathering information to map contact networks; geolocating targets that use the satellites; eavesdropping on data communications; prepare for or actually do jamming or spoofing activities; or checking these satellites for vulnerabilities that might provide a means to disable them, might need come.

 

UPDATES 5 and 7 July 2024

The westward drift of LUCH (OLYMP) 2 stopped on July 1, at longitude 0.54 W, where it has now stabilized its position. LUCH (OLYM) 2 is now close to the Norwegian commercial geosat THOR 7 (2015-022A). Due to bad weather, I have not been able to image it there yet. I imaged it at its new position on July 6/7, see this new blogpost.

The North Korean satellite Malligyong-1 raised its orbit again early June

 

click diagram to enlarge

Early February 2024, the North Korean satellite Malligyong-1 (2023-179A) made a series of orbital raising manoeuvers, the first we have ever seen a North Korean satellite do. I wrote about the character and significance of it at the time in two brief articles in The Space Review, which you can read here (part 1) and here (part II).

And now Maligyong-1 has raised its orbit again, in early June, slightly over 3 months after the February orbit raise. As was the case for the February orbit raise, it was done in five increments, one on each successive day, the first incremental raise in this series happening on June 3 and the last on June 7, 2024. The fifth and last of the June incremental raises also raised the apogee, by 1.6 km, something that did not happen during the previous orbit raise in February.

click diagram to enlarge

 

Each incremental raise raised the average orbital altitude by about 1.15 kilometer, for a total orbit raise of 5.8 kilometer. Perigee was raised by 10 km in total, apogee by 1.6 km. The series of incremental raises lifted the orbit to 504 x 502 km. The average orbital altitude was lifted to 503 km, half a kilometer higher than the initial insertion orbit from November 2023 (see diagram below). The new manoeuvers also further circularized the orbit (see diagrams above).

As was the case for the February manoeuvers, the orbit raise effectively compensates for the loss in orbital altitude due to natural orbital decay since February (and since launch in November 2023), maintaining the orbit within the preferred operational altitude limits.

In addition to raising the orbit back to its initial altitude, and further circularization of the orbit, the current series of orbit raises also served to bring the rate of RAAN precession even closer to the ideal sun-synchronous value than it was before. The orbit has a repeating ground track after 76.007 revolutions, i.e. each 5 days.

click diagram to enlarge

 

From what we have observed so far, we now likely can expect periodic orbit maintenance raises to happen about each three months, The first orbit maintenance raise in February 2024 was three months after launch, and the current second orbit maintenance raise three months after the previous. 

The next orbit raise therefore probably will happen near mid-September 2024.  

Both in February and June, the first sequential raise was on a Monday and the last on a Friday. We might therefore likely see the next orbit raise initiate on Monday 9, Monday 16 or Monday 23 September, 2024.

Like I did for the sequential orbit raises in February, I tried to reconstruct the approximate moment and location for each sequential burn between June 3 and 7. 

For the February series of orbit raises, I found that all incremental raises appeared to correspond to late local evening passes within direct line-of-sight of the Satellite Control Center in Pyongyang (see this article in The Space Review). 

The tracking data available for this series are a bit more sparse than for those in February (especially around the third incremental raise), yet when doing a similar analysis for this series a very similar pattern emerges again: all manoeuvers occurred around 13h-14h UTC (22h-23h local time), one of two moments in the day when the orbital plane of the satellite is passing over North Korea.

click map to enlarge

Nominal calculated manoeuver locations (for the method, see here) are all either in the area where the satellite is above the horizon as seen from North Korea, or close enough to it that they in reality very likely were too, taking uncertainties into account. The third incremental manoeuver (green) does not, but tracking coverage around that specific manoeuver is sparse, so that determination is a bit suspect.

Each line on the map above depicts the satellite's ground track from 10 minutes before, to 10 minutes after the nominal calculated manoeuver moment. The red circle is the boundary of the range where the satellite is above the horizon as seen from Pyongyang. Two out of the five nominal calculated manoeuver positions are within this circle, three are not. But even though for these three the calculated nominal manoeuver point is not within this circle, the satellite would have passed within the circle within minutes of the calculated manoeuver time on two of the three occasions, as can be seen from the mapped T-10m to T+10m ground tracks.