Reentry predictions for the Chinese CZ-5B rocket stage 2021-035B [UPDATED]

UPDATE:

CSpOC/18th Space Control Squadron report that the CZ-5B rocket booster 2021-035B met a fiery end at 2:14 UT last night (May 9) over the Arabian peninsula and Indian Ocean. China reports reentry at 2:24 UT in the Indian Ocean near the Maldives

click map to enlarge

UPDATES 9 May 2021, 9:00 UT and 14:30 UT:

In the map above, I have plotted the approximate final trajectory (based on a SatEvo-evolved orbit propagated to reentry) and both the reentry locations reported by China (2:24 UT, 2.65 N, 72.64 E, in the Indian Ocean near the Maldives) and by CSpOC/18th Space Control Squadron (2:14 UT, 22.2 N 50 E, over the Arabian Peninsula).

Note how within minutes of the reentry, the rocket passed over the city of Riyahd in Saoudi-Arabia!

In looking at the plot, one should realize that a reentry is not an instantanious moment, but a process stretching over many minutes, where the object starts to break up and fragments burn up in the upper atmosphere. During this process, the object continues to move over a swat of trajectory that can be hundreds to a few thousands of kilometers long. It is very likely that this proces started over the Middle East or even over the Mediterranean already [edit: imagery from Jordan suggest that the object was still intact when passing over that location, but see a potential video from Oman below]. If fragments survived, they are scattered somewhere along the yellow line in the map, within the current uncertainties of the reentry location.

The video footage in the tweet below appears to show the (start of the) reentry, imaged from Oman, but is unverified for now:

وأخيرا سقط حطام #الصاروخ_الصيني

فيديو من سلطنة عمان يبين بداية دخوله للغلاف الجوي.

بحسب مصادر صينية، سقط الحطام في المحيط الهندي شمال المالديف.

بحسب مصادر أمريكية دخل الغلاف الجوي الساعة 02:14 أثناء مروره فوق سلطنة عمان وسقط الحطام أخيرا شمال المالديف. pic.twitter.com/aR6FEUHMd0

— مركز الفلك الدولي (@AstronomyCenter) May 9, 2021

I have tried, by fiddling with the area-to-mass ratio for the rocket in GMAT, to create a reentry trajectory that would match a splashdown in the Maldives around 2:24 UT, as reported by China. The closest I can get to the location reported by China is this result:

click map to enlarge

Of course, this is a simplified model (the proverbal "spherical cow in a vacuum") that does not take into account both mass loss from ablation and fragmentation over the reentry trajectory.

It however suggest that, if the time and location reported by China is right, the rocket stage would have been at an altitude of ~100 km around the position and time reported by CSpOC (the US military tracking network). It could be that the CSpOC position, with the quoted very small uncertainty in time of +- 1 minute, is based on a SBIRS satellite detection of the fireball (we have long suspected that TIP's with such 1-minute uncertainty quotes are based on satellite detections of the reentry fireball). 

About 100 km is a fair altitude for the ablative phase to start, similar to the altitude at which meteoric fireballs start. If the video from Oman above is the real deal, it is indeed suggested that ablation (and break-up) was starting over southern Arabia.

As a further update: interesting information about infrasound detections of the reentry from Djibouti, with source over the Arabian peninsula:

#CTBTO #IMS infrasound station IS19 #Djibouti🇩🇯 recorded an emergent, low-frequency signal of an object traveling at ~10000 km/h, compatible w/ re-entry of part of the #LongMarch5BRocket 🚀 over Arabian peninsula on 9 May @ 2:15 UTC & splash down in #IndianOcean near #Maldives pic.twitter.com/mlUlxtDI4b

— Lassina Zerbo (@SinaZerbo) May 9, 2021

[end of update]

(below is the  pre-reentry  version of this frequently updated post):

(this part below last updated 8 May 23:00 UT)

On 29 May  April, China used a CZ-5B rocket to launch the core module of it's new Space Station Tianhe-1 ("Harmony of Heavens-1"). The module was initially placed in a 41.5 degree inclined, 382 x 171 km orbit and subsequently raised to a 385 x 352 km orbit.

The massive CZ-5B core stage from the CZ-5B rocket used for this launch was left in a 375 x 170 km orbit. Like it's predecessor that flew in May 2020, it was not deorbited after payload release. This likely means that it will come down in an uncontrolled reentry somewhere on May 8 or 9.

Compared to 'normal' rocket upper stages (which are typically 3 to 10 meters long and say 1000-2500 kg in mass), the CZ-5B core stage is huge. It is 31 meters long, 5 meters in diameter, and very heavy: sources differ on the dry mass, but it is somewhere between 17 and 22 tons.

 

The informal Space industry standard for objects that are heavier than 10 tons, and launched into Low Earth Orbit, is to have a deliberate deorbit over an empty stretch of Ocean. This did not happen with the CZ-5B core stage from the 5 May 2020 launch a year ago, and does not seem to happen now following the Tianhe-1 launch either.

An uncontrolled reentry of an object this large and heavy means that sizable fragments can survive reentry and reach the surface of the earth, with the risk that this happens over inhabited parts of the world. This is not something that you want, from safety concerns. Several analysts have gone on the record calling the lack of a controlled reentry for the CZ-5B core stage 'irresponsible' for that reason.

I’ll just reiterate that uncontrolled re-entries of large rocket stages in 2021 is absolutely irresponsible behavior https://t.co/Q6RZAyFPpZ

— brianweeden (@brianweeden) April 30, 2021

Indeed, there are risks. For example, sizable fragments from the core stage of the previous CZ-5B launch, that also came down in an uncontrolled reentry, rained down on well populated parts of Ivory Coast in Africa in May 2020.

With the first lauch and uncontrolled reentry of a CZ-5B core stage a year ago, the question was whether a deliberate deorbit was planned but failed, or whether the CZ-5B core stage simply does not have a deorbit capability. As history now seems to repeat with this second CZ-5B launch, it starts to look like the CZ-5B indeed has no deorbit capability. This is highly surprising, and, indeed, irresponsible imho.

At the same time, while there is a risk (see what happened a year ago in Ivory Coast), the risk should not be overstressed. The risk that a random passenger aircraft ends up falling on your house is still orders of a magnitude larger, and we all have come to accept that risk.

We should also realize that much of the 17 to 22 tons mass of the stage will burn up before it reaches earth surface. Moreover, as a large part of the Earth consists of Ocean, it is likely that it will come down harmlessly over some Ocean.

Yet, it cannot be excluded that it will come down over a populated area, so some worry is justified. With an orbital inclination of 41.5 degrees, locations between 41.5 N and 41.5 S are in the danger zone for this reentry. The danger is slightly elevated at the extremes of this (41.5 N and 41.5 S). The latitude range where the CZ-5B booster can come down includes the whole of the United States, Australia, Africa, the southern parts of Asia and much of southern America. Europe is mostly safe, except for Spain, Italy and the Balkans:

 

When the reentry happens, the rocket stage will break up in the atmosphere and any surviving parts that have not burned up completely will rain down along the ground path along a very long stretch of earth: the area where fragments fall down can be hundreds of kilometers long.

 

PREDICTIONS

The diagram in the very top of this post gives reentry predictions. I will update it every time I run a new prediction. Below are the same predictions in table form. They are based on modelling of the orbital evolution in the General Mission Analysis Tool (GMAT).

Modelling is done for a mass of 17 tons (note that the true dry mass of the rocket stage is a bit uncertain: quoted values range between 17 and 22 tons, depending on the source) and with a drag surface at 60% of the maximum surface, as I have found that this generally fits well with tumbling rocket stages (which as a result of the tumbling have a variable drag surface). 

Each new prediction is based on a new orbital update from CSpOC. The MSISE90 model atmosphere is used, with past, current and estimated future Space Weather.

Note that these predicted reentry times are nominal values only. PLEASE NOTE THE VERY LARGE UNCERTAINTY IN THESE TIMES! 

The uncertainty margins shown are calculated as 20% of the time between the orbital epoch on which the prediction is based, and the predicted reentry time.

Note that the nominal position shown is only nominal: it is for the center of the uncertainty interval, but as long as the uncertainties in the reentry time measure in the hours, it is basically meaningless.

 

DATE      *NOMINAL* TIME        (issued)     (*nominal* position)

8 May     19:23 UT +- 22 hr     (May 4.22)

8 May     21:23 UT +- 21 hr     (May 4.46)

8 May     20:40 UT +- 21 hr     (May 4.53)

8 May     19:41 UT +- 20 hr     (May 4.59)

8 May     20:46 UT +- 18 hr     (May 5.08)

8 May     21:36 UT +- 18 hr     (May 5.20)

8 May     21:18 UT +- 16 hr     (May 5.51)

9 May     00:10 UT +- 16 hr     (May 5.58) 

9 May     04:40 UT +- 13 hr     (May 6.50)

9 May     03:52 UT +- 10 hr     (May 7.18)

9 May     04:01 UT +-  9 hr     (May 7.36)

9 May     03:36 UT +-  5 hr     (May 8.17)

9 May     03:10 UT +- 3.5 hr    (May 8.40)   (07 N 108 W)

9 May     03:11 UT +- 1.8 hr    (May 8.77)   (11 N 103 W)

9 May     02:54 UT +- 1.3 hr    (May 8.86)   (31 S 155 W) 
 

Uncertainties in the predicted reentry times will remain very large untill very shortly before the actual reentry.

click map to enlarge

Within the 2 hour wide uncertainty window of the current CSpOC TIP (9 May 2:04 UT +- 1 hr), which no doubt is more reliable than my amateurish efforts, the rocket stage can come down anywhere on the lines drawn in the map above (the lines show the rocket's trajectory over the uncertainty window). Within the risk window, the trajectory runs over central America, southern Europe, Arabia and the southern tips of Australia. China itself now appears to be out of the risk zone, ironically enough. The nominal point (but: with such a wide uncertainty that it is still basically meaningless!!!) is over Spain

The yellow dots in the map are those cities with populations of a million or more between 41.5 N and 41.5 S.

Other sources of predictions:

Most notably: Space-Track (the CSpOC portal: requires an account), which should be regarded as the most authoritive one.

Also: EU SST on Twitter

...and otherwise: Joseph Remis on Twitter, and Aerospace Corporation 

(note how all of these give somewhat differing forecasts: which shows you how difficult these reentry forecasts are!)

Several years ago I wrote a FAQ about reentries, and reentry predictions, that might answer any questions you have.

I will update this post with new data when I have the opportunity.

USA 314 (NROL-82) imaged

 

click to enlarge

Last Monday 26 April at 20:47:00 UT, ULA launched a classified payload for the NRO under the launch designation NROL-82. The payload is now designated USA 314. I wrote about the launch and that it is almost certainly an ADVANCED ENHANCED CRYSTAL KH-11 electro-optical reconnaissance satellite in an earlier post.

The payload was picked up on the first orbit by radio observer Scott Tilley in Canada, and next, guided by the radio observations, Cees Bassa (who is just like me in the Netherlands) optically imaged it on the second and third orbit.

Thanks to information from the radio observations, #NROL82 was caught in video observations on its second pass. It passed close to Polaris in the top left of this image at 23:45:30UTC. pic.twitter.com/HB8bSFy84e

— Cees Bassa (@cgbassa) April 27, 2021

 

I tried to image it from Leiden on the second orbit as well, but as it turns out it passed outside my camera field during that pass.

The next night, and with a more firm search orbit based on the data from the previous night available, I did succesfully image it. The photograph in top of this post was made with a Canon EOS 80D camera and Samyang 1.4/85 mm lens (at F2.0, 1600 ISO, 1 second exposure). 

I also obtained video, using the WATEC 902H2 Supreme with a 1.8/50 mm lens:

The payload is designated USA 314 (catalogue nr 48247, COSPAR 2021-032A) and as usual CSpOC does not publish orbital data. But our observations show that it is in a 528 x 755 km, 98.1 degree inclined sun-synchonous orbit.

The orbital plane is even closer to that of USA 224 than anticipated: a difference of only 1.1 degree in RAAN and 0.2 degrees in orbital inclination. The orbital altitude is somewhat different and the orbital eccentricity is less than our initial guess. Perhaps it will manoeuvre over the coming days/weeks to the same altitudes as USA 224, perhaps it will not: we will see!

So in all, the NROL-82 payload's orbit is pretty much what was expected, apart from a slightly different initial orbital altitude.

USA 224 and the new payload USA 314 currently move almost in phase, and as a result they are relatively close, with continuous sight of each other. It is well possible that USA 224 is imaging the new payload as a post-launch health checkup.

The image below shows the coplanar character of the USA 224 and USA 314 orbits, and the spatial proximity in viewing distance of each other:

click to enlarge

As I pointed out in a previous post, based on historical patterns I expect that, after a checkout-phase that may take a couple of weeks, the new USA 314 will take over from USA 224 in the KH-11 primary East orbital plane. USA 224 will then likely be manoeuvered into a lower orbit (~400 km) and its orbital plane will be moved to the 'secondary' East plane, some 10-20 degrees east in RAAN of the current orbital plane.

An upcoming French ICBM/SLBM test [UPDATED TWICE]

click map to enlarge

UPDATE (see end of post for more info): the test happened and it was an M51 SLBM

Navigational Warnings HYDROLANT 1140/21 and NAVAREA IV 337/21 which appeared today suggest that France will be test-firing some sort of ICBM or SLBM over the northern Atlantic between April 28 and May 21. 

As indicated by the position of area A, the launch will be from from DGA Essais de Missiles, a missile base of the French Military on the coast of the Gulf of Biscaye, some 70 km southwest of Bordeaux. The target area appears to be north of  Bermuda, some 5500 km from the launch site.

250005Z APR 21
HYDROLANT 1140/21(and NAVAREA IV 337/21)
NORTH ATLANTIC.
BAY OF BISCAY.
FRANCE. 
1. MISSILE OPERATIONS 0001Z TO 1000Z DAILY
   28 APR THRU 21 MAY IN AREAS BOUND BY:
   A. 45-30.00N 006-39.00W, 44-35.00N 001-28.00W,
      44-26.00N 001-16.00W, 44-18.00N 001-17.00W,
      44-14.00N 001-36.00W, 45-08.00N 006-45.00W.
   B. 47-33.00N 019-01.00W, 47-21.00N 015-35.00W,
      45-29.00N 015-33.00W, 45-41.00N 019-12.00W.
   C. 35-50.00N 070-08.00W, 35-50.00N 063-38.00W,
      34-15.00N 063-38.00W, 34-15.00N 070-08.00W.
   D. 46-38.12N 039-31.05W, 45-37.02N 039-15.53W,
      45-53.52N 036-47.10W, 46-54.92N 036-59.92W.
2. CANCEL HYDROLANT 1124/21.
3. CANCEL THIS MSG 211100Z MAY 21.

I have mapped  the four hazard areas from the Navigational Warning in the map in top of this post. Areas A, B and D are along a simple ballistic trajectory. Area C, the target area north of Bermuda, is not (as can be clearly seen), so either the post-boost vehicle or the dummy MIRV's fired from it will take a different course at some point. 

Note that the dog-leg which I have drawn in the map is very hypothetical and not very realistic: its purpose just is to show that the target area deviates from the initial missile trajectory. [added note: it is much more likely that the trajectory changed is effected much earlier in the  sequence]

Depending on the time of, and weather conditions during, this test launch, it might generate some UFO reports from the southwest French and northern Spanish coast.

As far as I am aware of, the French only have SLBM's in operational service at this moment. Their landbased ICBM's were mothballed in 1996. 

So the launch might be a (land-based) launch of an M51 SLBM. The ground range and size of the areas A,B and D with respect to to the launch site are similar to those of another recent French SLBM test, fired from a submarine in front of the Breton coast on June 12, 2020 (I wrote about that test here).

Click to enlarge

UDATE 1: 

I spoke with Joseph Trevithick for this article in The Drive which also has insights from several other experts.

What I did not know, but learned from the article, is that the DGA Essais de Missiles has a pool with a submerged launch platform, so they can simulate SLBM launches from a submarine. So if it is another M51 test, this makes the choice of the launch site less odd.

Here is some footage from an earlier SLBM test from this submerged platform at DGA Essais de Missiles:

UPDATE 2 (28 April 2021)

The French Ministry of Defense has announced that a successful test with an M51 SLBM was indeed conducted from DGA Essais de Missiles in the morning of 28 April. Bulletin (in French) here.

In the hours around the test, French and US military monitoring planes were in the air near the target area north of Bermuda:

.@GDarkconrad discovered a Cobra Ball missile tracking aircraft operation near Bermuda. Could it be to monitor possible French M51 flight test https://t.co/X2oXqkH6W0 first reported by @Marco_Langbroek ? Flight warning period opens today... pic.twitter.com/B3V0ouCseM

— Hans Kristensen (@nukestrat) April 28, 2021

Uhm, French Navy Falcon was up, maybe something to do with a certain French missile test ?
cc @Marco_Langbroek pic.twitter.com/bXpVB08Gvs

— DutchSpace (@DutchSpace) April 28, 2021

 

The twitter account of the French Direction générale de l'armement published this video of the launch:

La DGA a conduit avec succès un tir d’essai d’un #missile #M51 sans charge militaire, depuis le site Landes du centre d’expertise DGA Essais de missiles ce matin. Il s’agit du 5e tir d’essai réalisé par la DGA dans le cadre du programme M51 #NotreDéfense
➡️https://t.co/DbhJzWK0z3 pic.twitter.com/Qu94EfsqlV

— Direction générale de l'armement (@DGA) April 28, 2021

 

The image below, which is from the bulletin put out by the French Ministry of Defense, may or may not show the actual missile fired:

NROL-82: an upcoming new KH-11 EVOLVED ENHANCED CRYSTAL launch [UPDATED]

image: ULA

(updated 27 Apr 2021 with first observational orbit, see end of post)

If the weather and the launch Gods cooperate, ULA will launch a Delta IV Heavy with a classified payload for the NRO on 26 April 2021. The launch is designated NROL-82 and the payload will likely receive the designation USA 314. In a tweet from April 19, ULA mentions a prospective launch time of 20:46 UT.

Several lines of evidence lead us to believe that the payload is a KH-11 EVOLVED ENHANCED CRYSTAL optical reconnaissance satellite, colloquially also known as a 'Keyhole'. It is the kind of satellite that makes these kind of detailed pictures of areas of interest for the NRO.

A map in the ULA Mission Overview for this launch, and the Navigational Warnings issued for this launch (NAVAREA XII 173/21 and HYDROPAC 1221/21) provide information on the launch azimuth and from that the orbital inclination targetted. Likewise the position and time window of the upper stage deorbit area provides - in a very broad sense- information on the orbital altitude aimed for. Together they indicate a launch into a sun-synchronous Low Earth Orbit with an orbital inclination near 98 degrees. This is a very familiar orbit, as we will discuss later in this post.

Below is a map I prepared depicting the hazard areas from these Navigational Warnings as well as the launch trajectory I calculate based on this information:

click map to enlarge

The listed times along the track are for launch at 20:46 UT into the 250 x 1020 km, 97.9 degrees inclined estimated orbit below:

 NROL-82 (USA 314)          for launch on 26 April 2021 at 20:46:00 UT
1 70002U 21999A   21116.86527778  .00000000  00000-0  00000-0 0    03
2 70002 097.8600 222.0898 0548970 157.1680 337.2110 14.78203944    02

 

The text of the Navigational Warnings:

220434Z APR 21
NAVAREA XII 173/21 (also: HYDROPAC 1221/21)
EASTERN NORTH PACIFIC.
EASTERN SOUTH PACIFIC.
CALIFORNIA.
1. HAZARDOUS OPERATIONS:
   A. 2016Z TO 2257Z DAILY 26 THRU 28 APR
      IN AREA BOUND BY
      34-38N 120-40W, 34-36N 120-30W,
      34-07N 120-39W, 34-08N 120-44W.
   B. 2016Z TO 2257Z DAILY 26 THRU 28 APR
      IN AREA BOUND BY
      22-57N 120-46W, 23-47N 125-18W,
      26-27N 124-45W, 25-36N 120-08W.
   C. 2016Z TO 2257Z DAILY 26 THRU 28 APR
      IN AREA BOUND BY
      13-28S 121-20W, 10-47S 138-34W,
      00-47S 136-41W, 03-52S 119-54W.
   D. 2253Z TO 0029Z COMMENCING DAILY
      26 THRU 29 APR IN AREA BOUND BY
      63-14S 174-16W, 32-49S 159-58W,
      33-23S 156-28W, 64-16S 168-07W.
2. CANCEL THIS MSG 300129Z APR 21.

 

Area D from the Navigational Warnings, located in the southern Pacific Ocean, appears to be the deorbit area for the Delta Cryogenic Second Stage (DCSS). The DCSS deorbit takes place some two hours after launch, just after the start of the second revolution (with the deorbit burn happening over the Arctic, near the end of the first revolution).

As mentioned above, the orbit that seems to be targetted is one that is very familiar in terms of orbital inclination and sun-synchronous character. It is the typical orbit of a KH-11 EVOLVED ENHANCED CRYSTAL electro-optical reconnaissance satellite. Several years ago I discussed the KH-11 orbital constellation in depth on this blog ("Past and future of the KH-11 Keyhole/Evolved Enhanced CRYSTAL constellation" - 2013). As a side note, the type of rocket used to launch NROL-82 is consistent with a KH-11 launch too: the Delta IV Heavy has a long history of launching KH-11's.

Currently there are at least three, and possibly four active KH-11 satellites on orbit: USA 186 (2005-042A), USA 224 (2011-002A), USA 245 (2013-043A), and possibly USA 290 (2019-004A).  The latter, USA 290, is in an odd orbit for a KH-11 and its identification as a KH-11 is open to questioning (I will discuss this later in this blog post).

Historically (see "Past and future of the KH-11 Keyhole/Evolved Enhanced CRYSTAL constellation"), new KH-11 satellites are launched into one of two primary orbital planes some 48 degrees apart in RAAN: a "primary East" plane and a "primary West" plane. The time window and the 20:46 UT launch time given by ULA for the upcoming April 26 launch corresponds well with targetting the "primary East" plane. This orbital plane results in passes around local noon and midnight. The KH-11 satellite currently occupying this orbital plane is USA 224 launched 10 years ago in 2011.

 

USA 224 imaged in June 2014. click image to enlarge

KH-11 constellation (minus USA 290), situation mid-April 2021 (polar view). Click to enlarge

 

The orbital plane of USA 224 passes over the launch site of NROL-82, Space Launch Complex 6 (SLC-6) at Vandenberg Air Force Base, around 21:20 UT on April 26. This is a difference of some 35 minutes with the launch time (20:46 UT) from the ULA tweet.

In 2011, when USA 224 itself was launched to replace USA 161 in the primary East plane, the launch occurred some 20 minutes before the USA 161 orbital plane crossed over the launch site (a similar time difference would hence see launch around 21:00 UT for the upcoming April 26 launch).

If history is our guide, the following sequence of event will likely happen. To start with, NROL-82 will be launched into the KH-11 Primary East plane, with an orbital inclination of ~97.9 degrees and orbital altitude of ~250 x 1020 km, almost co-planar with USA 224. The illustration below shows the orbital plane situation around orbit insertion. Note the similarity of the orbital planes of NROL-82 and USA 224:

 

expected situation just after launch of NROL-82. click to enlarge

 

After a check-out period of a few weeks, the NROL-82 payload (likely designated USA 314) will take over the primary plane mission from USA 224, the satellite previously occupying this orbital plane. 

Next, after USA 314 has taken over its role, USA 224 will be moved away from the primary plane, into a new orbital plane with RAAN some 10-20 degrees East of the primary plane: the so called '"secondary East plane". It will also lower its apogee and take up a ~400 km altitude orbit. In this new orbit it will continue to be operational for several years, entering its extended mission phase. 

From this moment on, for the first time since the deorbit of USA 161 in the winter of 2014-2015, all the two primary planes and all the two secondary planes will be occupied by a KH-11 again. The orbital constellation will become something like that in the image below:

Approximate KH-11 constellation after expected rearrangement later this year. Click to enlarge

 

How about USA 290?

You will have noted that after a brief initial mention, I carefully left USA 290, launched in 2019, out of the discussion so far. So what about that object? Is it a KH-11?

USA 290 (2019-004A) was launched as NROL-71 from Vandenberg on a Delta IV Heavy on 19 January 2019 (see an earlier blogpost) and it was suspected by some noted analysts to be a KH-11. It however went into a weird, 73.6 degree inclined ~400 km altitude orbit that is not sun-synchronous and nothing like previous KH-11 orbits. So, had the NRO broken with the previous 'classic' pattern of the KH-11 orbital constellation and were they trying something new?

The identification of  USA 290 as a KH-11 never has been sitting well with me. The odd orbital inclination and non sun-synchronous character of the orbit gives few reasons to think it is an IMINT mission.

In light of the apparent return to the known 'classic' KH-11 constellation with the upcoming launch of NROL-82, I have again started to foster these doubts. Maybe USA 290 isn't a KH-11 after all but something else, something experimental (readers of this blog will have noted that the past 4-5 years, a lot of NRO launches appear to be experimental, going into 'new' previously unseen types of orbit. Some of these are, I suspect, radar imaging satellites).

Ted Molczan has recently suggested that USA 290 is a KH-11, and that its odd orbit is inspired by that of the notorious 'Misty' stealth IMINT satellites of the 1990-ies which were launched in ~65 degree orbits. Basically, he argues that USA 290 is a 'Misty' imaging satellite without the stealth!

I remain agnostic at best about the identity of USA 290. Perhaps, if new payloads are launched into similar orbits over the coming years, the picture will become more clear. For now, I regard USA 290 as an oddity, and not necessarily a KH-11.

UPDATE 27 Apr 2021 11:00 UT

Cees Bassa optically observed the NROL-82 payload on the 2nd and 3rd revolution. Radio observers including Scott Tilley are also tracking it.

Based on a hybrid optical/radio orbit computed by Scott Tilley, the orbital altitude is somewhat different than expected, the orbit less eccentric: but the orbital plane is even closer to that of USA 224.

The orbital plane is very close to that of USA 224 indeed: a ~1 degree difference in RAAN and 0.1 degree difference in orbital inclination.

Orbital altitude currently appears to be about 525 x 760 km, i.e. less eccentric than our initila pre-launch estimate. That of USA 224 is 256 x 997 km.

The NROL-82 payload might manoeuvre in the coming days and weeks in order to have it's apogee and perigee altitudes match with  that of USA 224.

click to enlarge

LUCH (Olymp-K), an eavesdropping SIGINT snooping around commercial comsats

 

click image to enlarge

Back in 2016, I published an article in The Space Review (A NEMESIS in the sky: PAN, Mentor 4 and Close Encounters of the SIGINT kind) about the mysterious US classified satellite PAN, and Mentor 4, another classified US satellite.

Both are SIGINT satellites launched in 2009, that are positioned close to commercial telephony communications satellites in GEO in order to eavesdrop on their communications. While Mentor 4 (an ADVANCED ORION) dedicatedly covers Thuraya 2, PAN (NEMESIS 1) moved from satellite to satellite in a 'roving' role every few months during the first 5 years of its operational existence. Its sister ship CLIO (NEMESIS 2) launched in 2014 has done pretty much the same.

But (of course) the USA is not the only country playing this game. In the same year that CLIO (NEMESIS 2) was launched, the Russian Federation launched LUCH (2014-048A), aka OLYMP-K or OLIMP-K. In 2015, in an essay in The Space Review, Brian Weeden pointed out that LUCH was roving from satellite to satellite too, possibly eavesdropping on their communications. This created headlines at the time. By all means, LUCH/OLYMP-K is the Russian equivalent of PAN and CLIO.

The diagram below shows the frequent repositionings of LUCH/OLYMP-K over the years ( a table with major repositionings is at the end of this post):

click diagram to enlarge

LUCH has recently (in the second week of February, 2021) been relocating from longitude 3 W to 8 W and is now positioned near EUTELSAT 8 WEST B (2015-039B). Before the relocation, it had been close to ABS-3A (2015-010A) for several weeks. 

I shot this image below on March 29th, when LUCH and EUTELSAT 8 WEST B were about 90 km apart:

 

click image to enlarge

The image was made with a CANON EOS 80D and Samyang 2.0/135 mm lens (10 seconds at 1000 ISO) and was a by-product of targetting MEV-2 and several classified objects in this stretch of sky.

The table below gives longitudinal positions for LUCH/OLYMP-K. The table focusses on major relocations.

Dates refer to he moments the longitude appears to get stabilized, and have generally been preceeded by a period of drift. Also indicated is what satellite was closest to LUCH/OLYMP-K at the start of each stable period. Note that in several cases, multiple satellites were close by and possibly targetted as well.

TABLE: positions of LUCH/OLYMP-K since late 2014 

DATE          LON      NEAR

17-02-2021    08.1 W   EUTELSAT 8 West B       2015-039B
06-11-2020    03.1 W   ABS-3A                  2015-010A
28-09-2020    04.9 W   Eutelsat 5W B           2019-067A
11-05-2020    01.1 W   Intelsat 10-02          2014-058A
28-03-2020    21.5 E   EUTELSAT 21B            2012-062B
28-11-2019    70.6 E   EUTELSAT 70B            2012-069A
22-10-2019    68.4 E   Intelsat 20             2012-043A
25-08-2019    65.9 E   Intelsat 17             2010-065B
01-07-2019    64.0 E   Intelsat 906            2002-041A
21-02-2019    60.0 E   Intelsat 33E            2016-053B
28-10-2018    57.0 E   NSS 12                  2009-058A
03-07-2018    49.9 E   Turksat 4B              2015-060A
07-06-2018    48.0 E   Eutelsat 28B            2008-065B
27-04-2018    47.5 E   Yahsat 1B               2012-016A
17-01-2018    41.9 E   Turksat 4A              2014-007A
25-10-2017    38.1 E   Paksat 1R               2011-042A
18-08-2017    32.7 E   Intelsat New Dawn       2011-016A
14-09-2016    09.9 E   Eutelsat 10A            2009-016A
11-01-2016    01.1 W   Intelsat 10-02          2004-022A
05-10-2015    24.3 W   Intelsat 905            2002-027A
26-06-2015    18.1 W   Intelsat 901            2001-024A
22-02-2015    96.4 E   Express AM-33           2008-003A

[UPDATED] Cosmic Ballet: approach of MEV-2 and Intelsat 10-02 imaged

image from 2 April 2021. Click image to enlarge

At geosynchronous altitudes, a cosmic ballet is happening between Intelsat 10-02 (2004-022A) and MEV-2 (2020-056B). I imaged the pair last night, spurred to do so by Bob Christy. The pair was almost due south at 30 degrees elevation for me. 

 

click image to enlarge

click image to enlarge

 

A small complication was imposed by the current Corona-curfew, as it means I cannot go out to the spot where I normally photograph geosynchronous objects: so I had to target the camera through the loft window (which has a limited FOV).

MEV-2 ("Mission Extension Vehicle 2") is the second of Northrop-Grumman's satellite servicing missions. It's mission is to dock to Intelsat 10-02, a communication satellite launched in 2004, and extend the lifetime duration of this satellite by 5 years, providing it with fresh fuel and a new engine.

MEV-2 has made a number of close approaches to Intelsat 10-02 over the past weeks (see Bob Christy's detailed account of their movements on his website), in preparation for docking..

The MEV-2 predecessor MEV-1 successfully docked to Intelsat 901 in February of 2020 and then brought it from a graveyard orbit into an operational geosynchronous orbit. It also had to make several close approach attempts before effecting the docking at the time.

In the image above, I have labelled the brightest object as Intelsat 10-02 and the fainter one as MEV-2. Space-track has it the other way around, but according to observers who are following the duo for a while, they have mixed up the ID's. This often happens with objects close to each other in GEO, as it is acknowledgedly difficult to keep track of which is which. In this case, the brightness difference of the objects provide a  way to discern them. One expects Intelsat to be brighter than MEV-2.

The image is a 10-second exposure with a Canon EOS 80D and a Samyang 2.0/135 mm lens at ISO 1000.

UPDATE 1  30 March 2021 22:00 UT

I imaged MEV-2 and Intelsat 10-02 again this evening. They are still in the same relative position to each other as yesterday. The image below is a stack of 10 images (10s exposure each): the stack brings out the fainter MEV-2 a bit better than in yesterday's single image sabove.

click image to enlarge

Space-Track has, in their latest orbital updates, switched the identities back to what they should be, now designating the fainter object as MEV-2. You'd almost say they read my tweets... ;-)

UPDATE 2, 2 April 2021 13:00 UT:

Lats night was clear, so I imaged the duo again, after they came out of earth shadow. Due to the good phase angle, they were quite bright. Several other geosats visible in the vicinity as well. The image below was shot at 00:52:57 - 00:53:07 UT on April 2 (1600 ISO, 10 seconds, Canon EOS 80D + Samyang 2.0/135 mm):

click image to enlarge

[UPDATED] Reentry predictions for the Falcon 9 RB 2021-017BN

click diagram to enlarge

In my previous post, I discussed 2021-017BN, the Falcon 9 upper stage from the March 4 Starlink launch that should have been deorbitted after 1.5 revolutions on March 4th, but didn't.

It is still on orbit. At the moment of writing, 23 March 2021 at 11:00 UT, it is in a 217 x 200 km orbit according to the latest available elements from CSpOC, and it will stay on orbit for a couple of days to come. But the end is near: the orbital altitude of the rocket stage is quickly decaying, as can be seen in the diagram below:

click diagram to enlarge

My current reentry prediction (see diagram in top of post and table below) is that it will come down in the early hours of March 26 (2021). My prediction, based on modelling in GMAT R2020a using the MSISE90 model atmosphere, appears to be well in line with the TIP from CSpOC so far.

[UPDATE: my final post-cast predicted reentry at 26 Mar 04:34 UT, which is some 35 minutes too late. It is based on a 2/3rd maximum drag surface value. Interstingly, using the maximum drag surface leads to a reenrty at 3:56 Ut, within minutes f the actual time]

Revisit this post for prediction updates in the coming days.

orbit epoch     pred. date     reentry time (UT)
21081.600725    26 Mar 2021    02:33 +- 16.8 hr
21081.922054    26 mar 2021    03:36 +- 15.5 hr
21082.113317    26 Mar 2021    03:59 +- 14.7 hr
21082.216601    26 Mar 2021    03:40 +- 14.1 hr
21082.278149    26 Mar 2021    03:43 +- 13.8 hr
21082.462749    26 Mar 2021    05:29 +- 13.3 hr
21082.585776    26 Mar 2021    05:29 +- 12.7 hr
21082.708770    26 Mar 2021    05:37 +- 12.1 hr
21082.954651    26 Mar 2021    06:13 +- 11.1 hr
21083.138960    26 Mar 2021    05:03 +-  9.9 hr
21083.261785    26 Mar 2021    05:15 +-  9.4 hr
21083.296296    26 Mar 2021    05:20 +-  9.2 hr
21083.507296    26 Mar 2021    05:28 +-  8.3 hr
21083.875164    26 Mar 2021    05:26 +-  6.5 hr
21084.120127    26 Mar 2021    05:59 +-  5.4 hr
21084.181325    26 Mar 2021    05:20 +-  5.0 hr
21084.486963    26 Mar 2021    05:00 +-  3.5 hr
21084.548018    26 Mar 2021    03:19 +-  2.8 hr
21084.974688    26 Mar 2021    04:46 +-  1.1 hr * post-cast
21085.095602    26 Mar 2021    04:34 +-  0.5 hr * final post-cast

UPDATE  26 March 2021  12:30 UT:

The reentry happened last night, over North America, and was widely seen from the US States Washington and Oregon, near 4:00 UT (March 26 UT: that is 9 pm on March 25 local time for that area).

CSpOC's final TIP places the reentry at 03:58 +- 1 min UT. This time matches the reports from Washington and Oregon well, and based on the last orbit it would indeed place the rocket stage near the NW United States coast.

The listed geographic position in the TIP, 24.5 N, 151 W, does however not match well (it is further down the track, near Hawaii, corresponding to the Falcon 9 position about 6 minutes prior to the observed reentry). We have  noted such discrepancies more often in recent TIP messages. In this case, I half suspect the position was that given by their reentry model, and they forgot to update it when the SBIRS detection of the actual reentry fireball came in.

click map to enlarge

My own final "post-cast" places reentry some 35 minutes after the actual reentry.

Here are some of the reentry sightings as reported on Twitter:

DID YOU SEE THIS? I have never in my life seen something so incredible. I am in awe. Just happened over Portland about 10 minutes ago. #LiveOnK2 pic.twitter.com/L9wLEXBrcW

— Genevieve Reaume (@GenevieveReaume) March 26, 2021

uuuuuhhhh holy shit we just saw this meteor shower across the sky?!?! #pdx pic.twitter.com/umaE0joW7J

— lynseylou (@lynseylou) March 26, 2021

 

UPDATE 2 April 2021 23:00 UT:

Debris has been recovered from this reentry. In Grant Country, Washington, a Composite Overwrapped Pressure Vessel (COPV) was found on farmland.

 

 

SpaceX recovered a Composite-Overwrapped Pressure Vessel from last week’s Falcon 9 re-entry. It was found on private property in southwest Grant County this week. Media and treasure hunters: we are not disclosing specifics. The property owner simply wants to be left alone. pic.twitter.com/dEIQAotItY

— Grant County Sheriff (@GrantCoSheriff) April 2, 2021

Apparent failed deorbit of the Starlink-18 Falcon 9 upper stage [UPDATED]

On 4 March 2021, after several delays, SpaceX launched the 18th Starlink batch (Starlink-18 or V1.0-17). While the launch and deployment profile appears to have been similar to other recent Starlink launches, it appears that something went wrong with the Falcon 9 upper stage near the end of its mission.

On March 8th, Polish observer Adam Hurcewicz reported a bright, fast object in the orbital plane of this launch, passing a few minutes before the main Starlink "train". It was seen on subsequent nights and by other observers as well: the video above is from the early morning of March 9. At it's brightest, this fast moving object reportedly reaches mag -3. It does not appear to match a known object from earlier launches. It also didn't match supplementary TLE's for the Starlink-18 payloads from Celestrak (which are based on State Vectors from SpaceX). The Polish observers therefore speculated it was the Falcon 9 upper stage from the launch. 

But that would be against expectations. The Falcon 9 upper stage normally does not stay in orbit: it is de-orbitted soon after payload release, usually about 1.5 revolutions (about 2.5 hours) after launch. So if this object is the Falcon 9 upper stage, this suggests  something went wrong and it failed to deorbit.

The speculation that this object is the Falcon 9 Upper Stage can now be bolstered by additional information. The first orbital element sets for this Starlink launch have appeared on the CSpOC portal  Space-Track late yesterday (11 March), with catalogue numbers ranging from 47722 to 47786. And they show an extra object!

With Starlink launches, 64 objects are usually catalogued: 60 payloads and four 'Falcon 9 debris' pieces. The latter 'debris' pieces are the payload stack retaining rods: four metal rods which keep the satellite stack together on top of the upper stage. They are jettisoned upon payload release.

An elset for the Falcon 9 upper stage is usually not released by CSpOC: as it normally stays on-orbit for barely more than 1 revolution, it is not catalogued.

But this time, not 64 but 65 objects have been catalogued. The extra 65th object must be the Falcon 9 upper stage, and it indicates it stayed on orbit for more than a few revolutions. Which lines up with the observations by the Polish (and later also other) observers.

Although the 65 objects, at the moment of writing, do not have been individually ID-ed by CSpOC yet (all have the temporary designation "TBA - TO BE ASSIGNED"), the 60 payloads, four retaining rods and the upper stage as such can be clearly identified among them. The objects separate in 3 groups in terms of orbital altitude. The 60 payloads all have (for orbits with epoch 12 March) a perigee above 280 km. The four retaining rods have clearly lower orbits: their perigee is near 243-246 km and apogee near 268-278 km.

The 65th object, which by inference must be the Falcon 9 upper stage, is in a still lower orbit . It has the smallest semi-major axis of all of them with perigee near 237 km and apogee near 270 km. The orbit for this object, catalogue nr 47782 (2021-071BN) also closely matches the observations by the Polish observers.

So why is the Falcon 9 upper stage still on-orbit? It suggests of course that the deorbit went not as planned, i.e. it failed for some reason (e.g. the rocket engine refusing to restart).

That the Falcon 9 upper stage should have deorbitted on March 4, after 1.5 revolutions, is clear from the Navigational Warnings that were issued in connection to this launch. Navigational Warning HYDROPAC 695/21 delineates the usual elongated deorbit zone in the Indian Ocean familiar from earlier Starlink launches:

 

021948Z MAR 21
HYDROPAC 695/21(GEN).
SOUTHERN INDIAN OCEAN.
1. HAZARDOUS OPERATIONS, SPACE DEBRIS
   041024Z TO 041326Z MAR,
   ALTERNATE 051004Z TO 051306Z MAR
   IN AREA BOUND BY
   29-43S 060-07E, 24-55S 064-27E,
   38-45S 084-30E, 45-12S 099-45E,
   49-46S 119-13E, 50-42S 138-19E,
   48-50S 156-44E, 51-46S 158-08E,
   54-42S 148-32E, 56-20S 131-03E,
   55-52S 107-50E, 49-11S 085-05E,
   34-32S 064-13E.
2. CANCEL HYDROPAC 685/21.
3. CANCEL THIS MSG 051406Z MAR 21.

I have plotted the zones from the Area Warnings connected to the launch in this map, along with the groundtrack for the first 1.5 orbital revolutions. The large elongated red zone in the southern Indian Ocean is the planned deorbit area from Navigational Warning HYDROPAC 695/21:

click map to enlarge

The position of the reentry hazard zone indicates a reentry was planned around 10:55 UT (March 4), 1.5 revolutions (2h 30m) after launch, following a deorbit burn some 30 minutes earlier.

But the deorbit evidently did not happen as it should have: the upper stage is still orbiting as we speak, a week after launch. The issued Navigational Warning for the deorbit hazard zone strongly suggests this is not intentional.

So how long will the upper stage stay in orbit? The current orbit is low (237 x 271 km), and the object is large (16 x 3.66 meter, with a mass of 4.5 tons) so eventually the rocket stage will have an uncontrolled reentry, somewhere between latitudes 53 deg N and 53 deg S. 

A first assessment using both SatEvo and a GMAT simulation suggests that the reentry will probably happen in the last few days of March or the first few days of April.

UPDATE 14 March 2021:
CSpOC has now added identifications to the objects, and indeed object 47782 is now listed as "Falcon 9 RB"

A possible (now CONFIRMED) Trident-II SLBM test launch between February 9 and 14, 2021 [UPDATED]

click map to enlarge

A Navigational Warning, NAVAREA IV 117/21, appeared yesterday, and is suggestive of an upcoming Trident-II SLBM test in the Atlantic. I have posted on such test launches before.

This is the text of the Navigational Warning:

 071431Z FEB 21
 NAVAREA IV 117/21(GEN).
 ATLANTIC OCEAN.

 1. HAZARDOUS OPERATIONS, ROCKET LAUNCHING
    091340Z TO 140226Z FEB IN AREAS BOUND BY:
    A. 28-56N 76-17W, 28-56N 75-34W,
       28-36N 75-34W, 28-43N 76-17W.
    B. 28-02N 73-18W, 28-17N 73-13W,
       27-47N 71-11W, 27-34N 71-17W,
       27-44N 72-10W.
    C. 26-25N 67-23W, 26-47N 67-10W,
       25-44N 63-47W, 25-06N 63-57W,
       25-32N 65-52W.
    D. 17-10N 45-30W, 17-37N 45-11W,
       16-53N 43-06W, 15-23N 41-22W,
       14-46N 41-42W, 16-11N 44-26W.
    E. 06-00S 09-39W, 05-13S 09-08W,
       06-37S 06-56W, 07-17S 07-22W,
       06-55S 07-57W, 07-00S 08-05W.
 2. CANCEL THIS MSG 140326Z FEB 21.

The map in top of this post shows the hazard areas A to E from this Navigational Warning plotted, and a fitted ballistic trajectory. Together they define what strongly looks like a Trident-II Submarine Launched Ballistic Missile (SLBM) trajectory. 

Area 'A' is the launch area where the submarine is located; areas 'B', 'C' and 'D' is where respectively the first, second and third stages of the missile splash down; area 'E' is the target area of the warhead(s).

The indicated range, from the distance between area's A and E, is about 8400 km. That is somewhat shorter than most earlier Trident-II tests in the Atlantic.

Earlier tests in the Atlantic typically had a range near  9800 km, in one case even 10 600 km (see my overview here). So this test falls short from a  typical test by about 1500 km. 

An earlier clearly shorter range was however indicated for the infamous June 2016 Royal British Navy Trident-II test, which would have had a 8900 km range with a target area west of Ascension Island if it had not failed. The range of the upcoming February 2021 test is 500 km shorter than that of this June 2016 test, with a target area slightly more north and the launch area further out of the Florida coast. 

The launch area is nevertheless a familiar one: one of two areas regularly used for Atlantic Trident test launches. 

It is the same as that for the 10 Sep 2013, March 2016 and June 2018 Trident tests. It is the area labelled 'launch area B' in the map below, which plots the launch areas of several previous Trident tests. The figure comes from this previous post and is discussed there (including a suggestion for why there might be two distinct launch areas).

click map to enlarge

 

The target area near Ascension Island and shorter range might perhaps indicate that this will be a British Royal Navy test with the SLBM launched from a Vanguard-class submarine rather than a US Navy test, but this is by no means certain. It could also mean a US Navy test with new hardware, e.g. a more heavy dummy warhead or a new stage engine.

US Navy tests are usually acknowledged after the test, so it will be interesting to see whether such an acknowledgement will appear from either the US or British Navy.

UPDATE  10 Feb 2021 10:50 UT

Overnight, images and footage have appeared from Florida and Bahama residents that show an exhaust plume, indicating that the test indeed took place, near 23:30 UT on Feb 9. These are a few of them:

Is this what we saw last night from the Leeward end of Provo? This is looking northeast at around 6:31pm yesterday (Feb 9, 2021) pic.twitter.com/yr8ReXUoZe

— Dave Wickert (@DaveWickert) February 10, 2021

JUST IN - Trident missile launched from a submarine just off the coast in South Florida?pic.twitter.com/odlkSaaRPT

— Disclose.tv 🚨 (@disclosetv) February 10, 2021

Strange Object appear in sky 2hrs ago in Palm Beach Florida, did my research & no rocket was launch today either, the next rocket launch is March 25th. #UFO #UFOsighting pic.twitter.com/d5uqmuJFUD

— Nick Thomas (@Mixmasterxl) February 10, 2021

Yippy presents launch footage of Trident II - #SLBM from Bahamas 2/9/2021 @ approx 1830hrs. pic.twitter.com/tqPbh5BZyG

— Yippy.com the best search engine in the world. (@yippycom) February 10, 2021

 

The imagery shows the sun-illuminated exhaust plume of the missile. The missile itself is in space by that time, ascending towards its ~1200-1800 km apogee.

I did a quick calculation: for a launch at 23:30 UT on 9 February 2021, the missile (and its expanding exhaust plume) should break into sunlight about a minute after launch once above ~147 km altitude. I have indicated the sunlit part of the trajectory in the map below in yellow. This means that the exhaust plume on the imagery is from either the second or third stage of the missile.

click map to enlarge

UPDATE 16 Feb 2021:

The Drive reports that the US Navy has now confirmed that this was a Trident test. The name of the submarine from which the missile was launched has not been released.

Virgin Orbit to launch first satellite for the Royal Dutch Air Force this year

 

Brik-II patch (collection author)

Today, Virgin Orbit and the Dutch Ministery of Defense announced that Brik-II, the first satellite owned by the Royal Dutch Air Force (RNLAF), will be launched this year on an upcoming LauncherOne mission.

Brik-II is a 6U cubesat that will host various experiments, reportedly including communications relay, space weather determination, and ELINT. Brik-II was built for the RNLAF by ISIS/ISISpace. Launch was originally scheduled for 2019.

About the launch, Virgin Orbit notes that :

"As part of the Netherlands’ broader plan to pursue a responsive space capability, RNLAF, Virgin Orbit and ISIS will pursue a demonstration of “late-load” integration, mating the payload to the rocket shortly prior to launch. This exercise will prove critical in pioneering the payload processing capabilities required to execute responsive launch"

The satellite is named after a previous pioneering Brik: Brik was the name of the very first aircraft of the "Luchtvaartafdeeling" ("Air Department") of the Dutch Army, a forerunner of the Royal Dutch Air Force. This first Brik was built by Martinus van Meel in 1913.

This is that first aircraft called Brik, photographed in 1916 with Lt. Versteegh behind the stick:

The first Brik. Collection Netherlands Institute for Militairy History (NIMH)

"Brik" is a facetious name used in Dutch for both an old cart, old car or old bicycle, as well as a two-masted sailing vessel (the English 'Brig'), and a word used for a poor quality building brick (hence the patch in top of this post).

First optical observations of the NROL-108 payloads USA 312 and USA 313

In the early morning of January 9, I made the my first optical observations of the two payloads, USA 312 and USA 313 (2020-101A & B)  from the December 19 NROL-108 launch (see my earlier post here for more info on this somewhat enigmatic launch). Both were bright: USA 313 was about magnitude +4.5 and USA 312 about +5.5.

Radio observers already detected one of the payloads on December 20, and the second on January 5th. I used their preliminary TLE's to optically hunt for the objects this morning, which saw a clear frosty sky in Leiden. [edit: as it turns out, Russell Eberst observed both objects one day before me. I somehow had missed that]

USA 313, the leading object, was 13 seconds early and as much as 2.4 degrees off-track relative to the January 5 radio elset. USA 312, the chasing object, was about 1 second early and half a degree off-track relative to the January 5 radio elset.

USA 312 was about 2 minutes behind USA 313. Their orbits are co-planar and on the same orbital altitude, and the true distance between the two was about 900 km at the moment of observation. They are likely meant to operate as a pair, and it will be interesting to see whether they will perform any proximity manoeuvres in the future.

A second fainter object chased USA 312: this turned out to be STARLINK-1632. Their close proximity is almost certainly coincidence, and the result of the increasing number of Starlink satellites on orbit.

The video in the top of this post, shot with a WATEC 902H2 Supreme and Samyang 1.4/85 mm lens, shows USA 313 first, and then USA 312 with Starlink-1632 close by.

 

Click image to enlarge