Friday, 27 November 2020

USA 310 (NROL-31) and it's Centaur on 25 November

click image to enlarge
 

The image above was taken between 1:28:22 - 1:28:27 UT on November 25, and shows both USA 310 (the NROL-101 payload) and its Centaur upper stage in one image. 

At the moment of imaging they were only some 48 arcminutes apart in the sky. Their real distance to each other was ~541 km. The image was made with a Canon EOS 80D and Samyang 2.0/135 mm lens.

Since launch the Centaur, which is is a somewhate lower, more eccentric orbit than the payload, has gained one complete lap on the payload, and it was overtaking it while I was imaging them in the early hours of  November 25. Their closest approach (at a very safe distance of 533 km) was  a few minutes after the image above, at 1:33:29 UT (25 November 2020).

Note the brightness difference between the two, the Centaur upper stage being clearly brighter than the payload. In this image, the Centaur is near the peak of its periodic brightness variation. In a previous post I have detailed the character of the brightness variation of the Centaur.

Tuesday, 24 November 2020

Brightness variation of the NROL-101 Centaur upper stage from video observations

 In my previous post I discussed our tracking of the recently launched NROL-101 objects: the payload (USA 310, 2020-083A) and the Centaur upper stage (2020-083B). The latter is variable in brightness (which is one reason why we think it is the Centaur), and I included a preliminary flash period determination of ~140 seconds in that post, based on analysis of my photographs.

click diagram to enlarge

 

I can now revise this to 138.02 seconds peak-to-peak, as the result of video observations on 22 November. The Centaur was semi-continously imaged over a 23-minute period, covering 10 brightness peaks, with a WATEC 902H2 Supreme and Samyang 1.4/85 mm lens. Photometric analysis with TANGRA yielded the curve above. 

The brightness diagram starts around the time of zenith passage, at an elevation of 87.6 degrees and ends at an elevation of 56.3 degrees. The phase angle changes from 30.6 degrees at the start to 32.3 degrees at the end, the range from 10525 to 11254 km.

The fitted sinusoid gives a peak-to-peak periodicity of 138.02 seconds. The rocket stage varied between roughly magnitude +6 and +8.5 in brightness. The corresponding absolute magnitude, given the range and phase angle, is +2.0 (peaks) to +4.5 (valleys). 

In the first 'valley' in the curve, there is a brief specular flare. Likewise, there seems to be a narrow steep feature on the top of the brightness peaks.

Filming was done at 25 frames/second. A brightness determination was done at every 4th frame. The curve shows 3-point running averages of these determinations.

The calibration from Red magnitude to Visual magnitude is provisional. Gaps in the curve are periods without data, due to e.g. repositioning of the camera field.

Sunday, 22 November 2020

Tracking objects in MEO from the NROL-101 (USA 310) launch [updated]

 

NROL-101 payload USA 310. Click image to enlarge

On 13 November 2020 at 22:32 UT, the United Launch Alliance (ULA) launched NROL-101 for the National Recconnaissance Office (NRO) from SLC-41 at Cape Canaveral. CSpOC catalogued the payload as USA 310 under #46918 (2020-083A) and also catalogued the Centaur r/b as #46919 (2020-083B). The payload is classified and orbital elements for both the payload and Centaur were withheld, as is usual for NRO launches.

I wrote about this mission in an earlier post. Initially, we thought that this satellite was perhaps a new SDS and would be launched into HEO (a 63-degree inclined 'Molniya orbit'). Subsequent observations of a fuel vent by the Centaur upper stage seen from the western USA four hours after launch did not seem to fit this, and made us speculate whether the payload perhaps was something new and went into a 58 degree inclined MEO (see the discussion at the bottom of this previous post).

The latter speculation turns out to be correct. On November 18, I imaged an object in a 58.5 degree inclined, 11034 x 11067 km Medium Earth Orbit (MEO). It was steady in brightness. The image in top of this post shows the object in a 6-second exposure with a Canon EOS 80D with Samyang 2.0/135 mm lens. 

Observing conditions on this night were very dynamic: at one moment it could be completely clear, then two minutes later completely overcast, and five minutes later completely clear again.

Two night later, on November 20, I imaged a second related object, in a slightly lower 58.8 degree inclined 10510 x 11043 km Medium Earth Orbit.  Below is one of my images:


NROL-101 Centaur RB. Click image to enlarge


This object is slightly variable in brightness, indicating a slow tumble and during it's peaks it is brighter than the first object. The brightness variation has a peak-to-peak period of 140 seconds. Below, the brightness variation can be seen in a 19-image stack:


click to enlarge

A diagram of the measured pixel brightness of the trails in a series of images, shows the mentioned periodicity, and also shows thge presence of a more specular peak at the tops of the curve:

(click diagrams to enlarge)

(note added 24Nov: an update to this curve from video observations, yielding a 138.02 second peak-to-peak period, is here).

For the moment, we interpret the first, steady object in the 58.5 degree inclined orbit as the payload (USA 310), and the second variable object in the 58.8 degree inclined orbit as the Centaur upper stage.

Here is a TLE for the payload, based on a 3.2-day observing arc:


1 46918U 20083A   20326.25970612 0.00000000  00000-0  00000+0 0    08
2 46918  58.5335 293.1790 0007646 263.2891  96.6658  3.77323127    09

RMS 0.01     arc Nov 18.17 UT - Nov 21.37 UT

The orbit repeats in a 3-4-3 days pattern.

 

Here is a very preliminary TLE for the Centaur RB, based on a short 43-minute observing arc, hence the values for the eccentricity and Mean Motion still are privisional values:

1 46919U 20083B   20325.05807551 0.00000000  00000-0  00000+0 0    07
2 46919  58.8264 292.5498 0070000 327.1858  32.4248  4.01148244    05


 

[update] Here is an updated elset for the Centaur RB based on a 3-day observational arc:

NROL-101 Centaur
1 46919U 20083B   20327.90329491 0.00000000  00000-0  00000+0 0    05
2 46919  58.8253 291.9447 0155268 103.5440 258.2387  3.86388179    00

RMS 0.02            arc Nov 0.14 UT - Nov 23.00  UT

 

The preliminary orbits match well with the fuel vent in Northern Saggitarius observed from Joshua Tree, California and Taos, New Mexico, on 14 Nov ~2:30 UT (18:30 local time in Joshus Tree). The positions match to within a few degrees:


click to enlarge [updated figure]





The orbit of USA 310 is decidedly odd. There have never been classified launches in such an orbit before. One commercial object was launched in a somewhat similar orbit (the orbital inclination is lower), the first (and only) of an ill-fated commercial communications network in MEO: ICO F2 (2001-026A) launched in 2001.
 

Click to enlarge [updated image]

 

Because this type of orbit is new for an NRO payload, it is probably something experimental, i.e. a technology demonstrator. We can only guess as to the function, although future orbital behaviour might shed some light. Options include: 

 

- Communications

- SIGINT

- SAR imaging

- Low resolution, wide area optical IMINT

- Space-Based tracking.

 

In seems that the last few years the NRO and associated organisations are experimenting a lot with new, experimental spacecraft and new types of orbit. We have seen a number of launches into ~50-degree LEO orbits for example (e.g. USA 276, and the failed ZUMA launch). Now unusual MEO orbits are added, it seems. It will be interesting to see how this object will behave, and if other payloads will be launched into a similar orbit in the future.

I, for one, welcome these new oddities: when things become too predictable, it gets boring. So yay for the new and unusual! 


ADDED NOTE (24 Nov):
 
Now that  both the payload and the Centaur r/b have been observed over a reasonable arc and the orbits have improved, I can provide an estimate for the separation of the Centaur and payload: 14 Nov ~1:00 UT, near the southern apex of the orbits. This was followed by an avoidance burn and fuel dump by the Centaur, so there is some leeway in this.


click to enlarge


Sunday, 15 November 2020

SM-3 Block IIA Missile Defense test FTM-44 against an ICBM-class target imminent, 17-19 November 2020 [UPDATED]

Click to enlarge. Image: MDA

Three days ago, on 12 November 2020, a Navigational Warning appeared that denoted three hazard zones in the northern Pacific for the period 17 to 19 November, connected to what clearly is some kind of missile test:

 

121041Z NOV 20
NAVAREA XII 509/20(GEN).
EASTERN NORTH PACIFIC.
NORTH PACIFIC.  
1. HAZARDOUS OPERATIONS 170400Z TO 171000Z NOV, 
   ALTERNATE 0400Z TO 1000Z DAILY 18 AND 19 NOV 
   IN AREAS BOUND BY:
   A. 09-12N 167-43E, 09-01N 167-40E, 
      08-58N 167-43E, 08-58N 167-48W, 
      09-00N 167-59W, 09-30N 168-18E, 
      09-43N 168-04E. 
   B. 11-22N 170-00E, 11-08N 170-10E, 
      11-44N 173-34E, 13-13N 176-53E, 
      15-39N 178-17E, 18-07N 179-23E, 
      18-48N 177-48E, 17-13N 174-19E,
      16-18N 173-08E, 13-08N 171-00E. 
   C. 44-06N 133-00W, 35-00N 131-00W, 
      28-30N 143-30W, 44-06N 140-30W. 
2. CANCEL THIS MSG 191100Z NOV 20.

 

I have plotted the three area's  in the map below. Note that there appears to be a clerical error in the Navigational Warning for two of the positions defining area A: those reading "W" should probably read "E", which results in a hazard area which makes much more sense (in the map below, the original, probably erroneous, shape for area A is depicted in red: what was likely meant in white).

(note added 17 Nov: an update to this Navigational Warning issued as HYDROPAC 3337/20 confirms the clerical error)

click map to enlarge

The location of the areas lead me to believe it points to a Missile Defense test: an attempt to intercept a dummy Ballistic Missile launched from Kwajalein towards the US main land. Area A denotes the immediate launch hazard zone for the dummy ICBM at Kwajalein; area B where the first second stage of the dummy ICBM will come down; area C the intercept area where the SM-3 interceptor will be fired and the intercept occurs.

Based on the location and shape direction of area C, I initially (and erroneously) thought it might be a Ground-Based Midcourse Defense test from one of the GBMD sites in Alaska. However, after some discussion with the Twitter missile community and some digging around, I am now quite confident that this is not a GMBD test, but an AEGIS SM-3 test, with the SM-3 intercept missile fired from a US Navy Destroyer located in the Pacific in the north of area C. Basically, the situation below:

Click to enlarge

(those of you who remember the infamous Operation Burnt Frost will know the Standard Missile 3 (SM-3): it was used to destroy the malfunctioned USA 193 satellite on 20 February 2008)

Indeed, a Missile Defense test with an SM-3 Block IIA missile, designated as test FTM-44, is known to have been originally scheduled in the Pacific for the third quarter of 2020.  It next was postponed due to the impact of the Corona pandemic, to late 2020

The Navigational Warning NAVAREA XII 509/20 that appeared three days ago now suggests that the FTM-44 test is imminent, and will take place between 17 and 19 November with the daily window running from 04:00 to 10:00 UT. The locations and shapes of the hazard zones designated in the Navigational Warning NAVAREA XII 590/20 fit well with what we know about the FTM-44 test (see below).

A US Naval Institute news release from August 2020 includes the following schematic graphic for FTM-44: compare this to the graphics above and note the clear similarity (note that my figure above is a view from the north,while the MDA figure below is a view from the south):


Click to enlarge. Image: MDA

Test FTM-44 will be the first attempt at intercepting an ICBM-class  missile rather than a MRBM, extending the system to include ICBM targets. AEGIS previously only included short- and medium range ballistic targets. From the position of area C, the intercept will take place at a range of about 6500 km from the Kwajalein launch site.

As can be seen from the MDA diagram above,  the test includes the use of Space-Based assets (satellites): the Space-Based Infra-Red System (SBIRS) for the initial detection of the launch of the dummy ICBM from GEO and HEO, and the Space Tracking and Surveillance System (STSS) for additional tracking of the ICBM missile through midcourse.

Satellites from the STSS system make passes with view of the test area around the following times during the 3-day test window:

Nov 17  ~04:15 UT
Nov 17  ~05:15 UT
Nov 17  ~06:15 UT
Nov 17  ~07:15 UT
Nov 17  ~08:15 UT
Nov 17  ~09:15 UT
Nov 17  ~10:00 UT

Nov 18  ~04:40 UT
Nov 18  ~05:40 UT
Nov 18  ~06:40 UT
Nov 18  ~07:40 UT
Nov 18  ~08:40 UT
Nov 18  ~09:40 UT
Nov 18  ~10:00 UT

Nov 19  ~04:05 UT
Nov 19  ~05:05 UT
Nov 19  ~06:05 UT
Nov 19  ~07:05 UT
Nov 19  ~08:05 UT
Nov 19  ~09:05 UT
Nov 19  ~10:00 UT


The US Naval Institute news release from August 2020 suggests that the FTM-44 SM-3 interceptor will be fired from the USS John Finn. This Arleigh-Burke class Destroyer will probably be located in the northern part of area C from the Navigational Warning.


USS John Finn. Image: US Navy (through Wikimedia)


UPDATE  (17 Nov 11:25 UT):

A news release from the Missile Defense Agency (MDA) has confirmed that FTM-44 has taken place this morning, and was successful. It states that the target was launched from the Ronald Reagan Ballistic Missile Defense Test Site at Kwajalein at 7:50 pm Hawaii Standard Time (=17 Nov 5:50 UT). With an approximately 21 minutes flight time, this should place the intercept near 6:11 UT (17 Nov 2020). [edit: but this assumes a typical ICBM speed, zo there is leeway in this time of intercept]

Between the time of launch and intercept, the STSS DEMO 2 satellite (2009-052B) was well positioned to track the target-ICBM mid-course (note: the position of the Destroyer that fired the SM-3 interceptor missile in the image below, has been assumed):

click image to enlarge

SECOND UPDATE:

Footage from the test has been released and can be seen here on the MDA website.

Graphic simulation of the test on the MDA website.

The MDA footage of the target launch and the MDA simulation linked above, confirm that the target ICBM was launched from 9.0065 N, 167.7270 E.


click to enlarge. Image: Google Earth

Acknowledgement: this blog post benefitted from discussions with Simon Petersen, Scott Lafoy and Ankit Panda.

Friday, 13 November 2020

Crew Dragon-1

click map to enlarge

[Edit 13 Nov 23:25 UT:  due to the weather the launch has been postponed one day to 16 Nov 00:27 UT]

If weather cooperates, SpaceX will launch Crew Dragon-1 for NASA from Cape Canaveral platform 39A on 15 November 00:49 UT 16 November 00:27 UT. Onboard will be be JAXA astronaut Soichi Noguchi and NASA astronauts Mike Hopkins, Shannon Walker, and Victor Glove. Docking to the ISS will be on 16 Nov 8:57 UT, 8.5 hours after launch. Docking to the ISS will be on 17 November around 4:00 UT

Unfortunately, the time of the launch means that it will not be visible during its pass over Europe some 23 minutes after launch: the pass is completely in earth shadow. In the map above  the dashed line is where the Crew Dragon is in earth shadow, the solid line where it is sun-illuminated. It will not be visible on the second and (for southern Europe) third pass either.

For radio observers: a TLE estimate for the first revolution is on the launchtower.

Sunday, 1 November 2020

NROL-101: probably a HEO mission [or maybe not! See update at bottom]


click map to enlarge


EDIT 4 Nov 2020 22:30 UT: 

post UPDATED with new maps and new value for inclination parking orbit

EDIT 2, 22:50 UT (Nov 4): the launch has been SCRUBBED for at least 48 hours...

EDIT 3, 7 Nov 22: launch is now currently scheduled for 11 Nov, 22:22 UT 

EDIT 4, Nov 13:  NROL-101 cleared the tower at 22:32 UT (Nov 13)


If weather cooperates,ULA will launch NROL-101, a classified payload for the NRO, on November 11 (postponed from November 3 and 4). Based on Navigational Warnings, the launch window is from 22:00 UT (Nov 11) to 02:45UT (Nov 12), with ULA indicating a launch window start at 22:22 UT. 

[ EDIT: eventually, NROL-101 launched on 13 Nov 2020 at 22:32 UT

The launch is from platform 41 on Cape Canaveral, using an Atlas V rocket in 531 configuration (5-m fairing, 3 strap-on boosters, 1 single engine Centaur upper stage). It would have originally flown in 551 configuration but this was changed. It is the first Atlas V flight to feature the new GEM 63 solid fuel strap-on boosters.

This Navigational Warning has appeared in connection to this launch (updated):


062038Z NOV 20
NAVAREA IV 1074/20(GEN).
WESTERN NORTH ATLANTIC.
FLORIDA.
1. HAZARDOUS OPERATIONS, ROCKET LAUNCHING
   112200Z TO 120245Z NOV, ALTERNATE
   122200Z TO 130245Z AND 132200Z TO 140245Z
   IN AREAS BOUND BY:
   A. 28-38-50N 080-37-34W, 29-58-00N 079-28-00W,
      29-54-00N 079-21-00W, 29-34-00N 079-36-00W,
      29-15-00N 079-45-00W, 28-36-00N 080-23-00W,
      28-30-57N 080-33-15W.
   B. 30-01-00N 079-33-00W, 31-08-00N 078-36-00W,
      30-54-00N 078-14-00W, 29-47-00N 079-11-00W.
   C. 36-38-00N 073-35-00W, 39-03-00N 071-00-00W,
      38-30-00N 070-13-00W, 36-05-00N 072-46-00W.
   D. 51-37-00N 049-45-00W, 53-32-00N 044-58-00W,
      52-54-00N 044-15-00W, 51-03-00N 049-07-00W.
2. CANCEL THIS MSG 140345Z NOV 20.
 

The launch azimuth from the location of the hazard zones in this Navigational Warning and the initial launch azimuth depicted in a map tweeted by ULA point to an initial lauch into a [value updated] ~56-degree ~57.75 degree inclined orbit:

 

click map to enlarge

However: this is likely only a temporary parking orbit. The 531 rocket configuration has never been used for a launch into LEO so far, but always for launch into GEO. Given the launch azimuth, NROL-101 will certainly not be launched into GEO. 

So either the payload is destined for LEO but unusually heavy or (more likely) the final orbit aimed for is a HEO orbit (also known as a  Molniya orbit) with inclination ~63 degrees, perigee at ~2000 km over the southern hemisphere and apogee near 37 8000 km over the Arctic. [But: see major update at bottom! It might have been MEO rather than HEO, but this remains uncertain!]

A 63-degree inclined Molniya orbit cannot be reached directly from the Cape, because of overflight restrictions. Hence the initial launch azimuth corresponding to a ~58-degree inclined orbit. If NROL-101 goes into a Molniya orbit, it will do a dog-leg some time after launch, or (more likely) coast in a ~58-degree inclined parking orbit for perhaps several hours before being boosted into a Molniya orbit by the Centaur.

This appears to be underlined by the fact that to date (Sunday Nov 1) no Navigational Warnings have been issued for the reentry area of the Centaur upper stage. This could indicate that the upper stage will be left orbiting in a ~2000 x 37 8000 km transfer orbit, or is disposed into a Heliocentric orbit.

The NRO so far launched three kinds of  satellites into HEO orbits:

1) Data communication satellites (SDS);

2) SIGINT satellites (Trumpet FO);

3) combined SIGINT (Trumpet FO) and SBIRS Early warning satellites.

The last SIGINT/SBIRS combination launched into HEO was USA 278, launched in 2017. The last SDS launch into HEO was USA 198 in 2007 (there was also a launch in 2017 but this was into GEO, not HEO). As Ted Molczan pointed out in  a private com, SIGINT launches into HEO usually were done from Vandenberg, SDS launches from Cape Canaveral. So perhaps NROL-101 will carry a new SDS satellite, but this is far from certain. Radio observations after launch might shed some light on both orbit and payload character.

The initial trajectory will take it over NW Europe some 23 minutes after launch, but in Earth shadow, so the pass will not be visible:


click map to enlarge

 

UPDATE 15 Nov 2020 15:20 UT

Around 2:30 UT on Nov 14, four hours after launch, sightings of a fuel venting event were observed from the western USA.

This image tweeted by  Marc Leatham shows the V-shaped cloud in Saggitarius, imaged from Joshua Tree National Park:



There is also allsky imagery of the fuel cloud from Taos, New Mexico (look low at the horizon where the milky way touches the horizon(right side), for a 'moving' piece of Milky Way. This is the fuel cloud):


These sightings lead us to believe that the payload perhaps went into the lower part of MEO, not HEO. This is however (emphasis) not certain at this moment.

The launch sequence then could have been insertion into a LEO parking orbit; an apogee raising burn; a perigee raising/circularization burn bringing it into HEO; and fuel vent/orbit separation burn by the Centaur rocket. That latter event caused the observed fuel cloud, at about 8500 km altitude.

ULA reported 'mission successful' around 1:48 UT. For the launch provider, their mission is completed upon payload separation. 1.48 UT corresponds to a pass through the southern apex of the orbit, suggesting payload separation was at that point. This, in combinbation with the observed Centaur vent, would argue against insertion into HEO but does fit insertion into MEO.

If my guess is correct, then this should be the approximate orbit (orbital position is the approximate position for the time of the Joshus Tree fuel cloud sighting):


click to enlarge

 

Both the Centaur and payload have been catalogued (but without orbital elements) by CSpOC, as #46918 (2020-083A) USA 310 and #46919 (2020-083B) Atlas V Centaur R/B.

If USA 310 indeed went into HEO, then the identity/character of the payload remains a big guess.


Added note, 4 Nov 2020, 21:30 UT: the maps and inclination of the initial parking orbit have been updated based on a map showing the initial trajectory up to fairing jettison tweeted by ULA boss Tory Bruno.

This post benefitted from discussions with Cees Bassa, Scott Tilley, Ted Molczan and Bob Christy.

Monday, 12 October 2020

North Korea's October ICBM surprise

click to enlarge. Screenshot from KCTV broadcast

Saturday 10 October 2020 saw North Korea's big military parade in PyongYang, connected to the 75th anniversary of the founding of the Workers Party of Korea. A nighttime parade this time, unlike previous years.

Those who follow the North Korean rocket and missile program always eagerly await these parades, as sometimes new missiles are presented. They were not disappointed this year.

The most interesting new missiles presented were a new version of the Pukkuksong SLBM and, at the very end of the parade, a surprise appearance of four immense 11-axle TEL's, each carrying a very large missile that appears to be a new Hwasong ICBM variant (see images above and below).

 

click to enlarge. Screenshot from KCTV broadcast
 

This missile at first sight looks like a larger variant of the flight-proven Hwasong 15 from 2017 (several of which were also shown in the parade). Below is my attempt at getting dimensions for this potential new ICBM:

 

click to enlarge

First, some caveats with this dimensional analysis:

* I had to work from a limited resolution screenshot I took from the KCTV broadcast;

* The baseline used is based on a Google Earth measurement;

* The image is wide angle and has some barrel distortion. This means that the straight sightlines I have drawn, are an approximation.

All these points will cause uncertainties in the measurements, so don't take them too strictly. Behind the decimal, they are probably no more accurate than to 0.2 meter or perhaps even worse.

The dimensional baseline I used is the distance from the stair entrance at left to the center of the area between the grass borders. The platform with stairs is visible on a Google Earth image, and I measure a distance of ~26.25 meter to the square center line, which is used as the base referal length here (please note: I assumed the two patches of grass are at equal distance to this centerline. Similar for the area with the orchestra at the other side of the road).

In this way, I get the following approximate dimensions:

* 25.6 meter for the total missile length (not counting nozzle);

* 2.7 to 2.8 meter for the first stage diameter;

* 2.3 meter for the base diameter of the nose fairing/Post Boost Vehicle;

* 30.5 meter for the TEL, from front bumper to the feet of the firing table;

* 16.9 meter for the first stage length (assuming it ends at the chequer-pattern);

* 4.5 meter for the second stage length.

As Jeffrey Lewis noted, the second stage appears to be slightly tapered in shape.

By comparison: the Hwasong 15 (test flown in 2017) measures 21.5 meter in length (not counting the exhaust nozzle) and is about 2.4 meter in diameter. 

Hence, this new Hwasong variant appears to be a factor of 1.2 larger in both length and diameter compared to the Hwasong 15. Several commenters have pointed out that this makes it the largest road-mobile ICBM ever.

As is usual, discussion has emerged whether this is a real missile, or just a fancy mock-up. There is still too much of a tendency, especially among an American audience, to regard North Korean missiles as all 'smoke and mirrors'. Given North Korea's 2017 track record with succesful Hwasong 12 IRBM and Hwasong 15 ICBM test flights, I do not think that the default reaction should be that this new missile must be a deception. Of course, we will only know for sure when we see it launched.

It will be interesting to see if, and if so when, this large missile is test-flown.

Friday, 9 October 2020

No, this reentry footage is not a fireball that appeared over Mexico on September 6/7

 

 

On 7 September 2020 near 2:14 UT (6 September 22:14 local time) a bright fireball appeared over Mexico, creating some media attention. As part of that attention, a video surfaced and was widely  retweeted, purporting to show this fireball. The image above is a screenshot of this video.

However: the object on this video is not the fireball from 7 September 2020

It is an 'old' recycled video from July 2020, showing a space debris reentry.

The video shows a very slow fragmenting object that is clearly reentering space debris. There was something familiar to it, which was one thing that raised my suspicion (I thought I had seen it before). The other thing that raised my suspicion was that this video clearly does not show the same object as other videos that showed up, which show the genuine September 7 fireball (like this one) .

Doing a Google Reverse Image Search quickly turned up Reddit posts from July 2020 (e.g. this one), featuring this same video, indicating that the footage was at least 2.5 months old (and hence definitely not the fireball of 7 September, confirming my suspicions).

The video does show a genuine reentry. The reentry in question happend on July 18th, 2020. The Reddit post linked above is from that date. Other video's of clearly the same reentry that was also seen from the USA posted on that date exist too.

And this is why the video looked so familiar to me: back in July I already identified footage of the same reentry as the reentry of a Russian Soyuz rocket stage (2019-079C), the second stage from the Soyuz rocket that launched the military Kosmos 2542 satellite on 25 November 2019. 

According to a CSpOC TIP message from July 18th 2020, this rocket stage reentered on 18 July 2020 07:02 UT (+/- 1 minute: this time accuracy indicates a SBIRS or DSP infra-red detection of the reentry) near 26.8 N, 101.2 W, over Northeast Mexico near the border with Texas. The map below depicts the final trajectory of the rocket stage and the CSpOC reentry position:

 

Click map to enlarge

This case highlights again that footage appearing on Twitter or other social media after an event  is not always what it purports to be, and one should always check whether it shows what it purports to show.

Wednesday, 30 September 2020

A very unusual fireball over NW Europe on 22 September 2020 (that went in and out of the atmosphere again)

 

The fireball of 22 sept 2020, ~3:53:40 UT. Image (c) Cees Bassa (stack of 2 images)

In the early morning of 22 September 2020, around 3:53:40 UT (5:53:40 local time), a very unusual long duration fireball appeared in the skies of NW Europe. It had a duration of over 20 seconds, and for several Dutch all-sky meteor camera's that captured it, it was a horizon-to-horizon event.

In this blog post, I provide a preliminary analysis of (mostly) Dutch camera records of this fireball. As it turns out, the meteoroid survived its brief passage through the upper atmosphere and came out unscathed at the other end!

The image above (which is a stack of two images, each showing a part of the trail) was captured by the all-sky camera of Cees Bassa in Dwingeloo, the Netherlands. The image below is one of several images captured by the cameras of Klaas Jobse in Oostkapelle. Other Dutch photographic meteor stations that caught it were that of the Bussloo VST (Jaap van 't Leven), Twisk (Marco Verstraaten) and Utrecht (Felix Bettonvil). Oostkapelle delivered both the sectored all-sky image below, and additional widefield images. A wide-angle image taken from Over in the UK by Paul Haworth was also kindly made available for analysis.

 

Click to enlarge

This was a fireball that entered the Earth's atmosphere under a very shallow, grazing angle: a so-called 'earthgrazer'. Because of the horizon-to-horizon aspect, I immediately suspected that this could be a very rare subcategory of 'earthgrazer': for a few of these have been known to enter the atmosphere, reach a lowest point above earth surface, and then leave the atmosphere at the other side again! 

 In other words, the situation of the schematic below:


 

The most famous case of this kind is the 1972 Grand Tetons daylight fireball (the first with instrumental records), but there have been a handful more since.

Analysis shows that the fireball from 22 September 2020 indeed belongs to this rare class of objects. The meteoroid approached the earth surface to a minimum distance of 91.7 km and then left the atmosphere again, on an altered orbit.

The Dutch photographic images plus Paul Haworths' image from the UK document some 745 km of ground-projected trajectory. The fireball moved from East-Northeast to West-Southwest, over Germany, the Netherlands, the southern North Sea basin and Britain. 

AOS from the photographic images was at 101 km altitude over Germany, around 53o.26 N 10o.22 E near Lüneburg just south of Hamburg. LOS was at 105 km altitude around 51o.98 N 0o.60 W, between Luton and Milton Keynes in the UK. 

The point of closest approach (indicated by a cross in the map below) was near 52o.80 N 5o.23 E at 91.7 km altitude above the geoid, over Lake IJssel in the Netherlands, not too far from the Twisk camera station which had it nearly overhead.

Click to enlarge

As this was a horizon-to-horizon event, it is likely that the actual trajectory started a bit more eastwards, and ended a bit more  westwards (although Paul Haworth's image shows that by the time it left view of his camera in the UK, the object was rapidly fading).

The plot below shows the atmospheric altitude of the fireball along its ground track. It reached a lowest point at 91.7 km (where it was moving parallel with the earth surface), and then moved away again, surviving the close encounter:

 

Click diagram to enlarge

Note that the trajectory was, of course, not as 'curved' as the diagram might suggest: the fireball was moving along a nearly straight path and the 'curve' in the diagram is in reality due to the curved earth surface below it (incidently proving again that Flat Earthers are wrong)!

The Twisk, Oostkapelle and Utrecht camera's had an electronic periodic "shutter" in front of the sensor, providing speed data for this fireball. The fireball entered the atmosphere with an initial speed of 33.6 km/s. It barely slowed down during it's grazing encounter with our atmosphere, leaving it again at a speed of ~30 km/s. It hence was too fast to be captured by the Earth: it moved on in a heliocentric orbit after the encounter.

The object was likely not particularly big. Some first quick calculations suggest something in the 20-40 cm range for the initial pre-atmospheric size (but this will need more study). The object was not very bright (Klaas Jobse, who saw it visually, estimated a brightness of magnitude -5) and it did not penetrate deep into the atmosphere. There will obviously have been some mass ablation, but probably limited: a sizable part of the original mass should have survived and moved along into space again.

The observed radiant of the fireball was near RA 163o.7, DEC +6o.4. It's geocentric radiant was near RA 165o.8, DEC +3o.5. The fireball hence came out of the direction of the sun (the sun was at RA 179o.4, DEC +0o.2 at that moment). 

click map to enlarge
 

The orbit calculated from the 33.6 km/s initial speed and the geocentric radiant of the fireball using METORB 10, is a short-period cometary orbit of the Jupiter family type (Tisserand 2.8) close to the 13:4 orbital resonance with Jupiter. The descending node of the orbit is close to Mercury, so it could have had close encounters to this planet in the past. Perihelion was at 0.30 AU, aphelion at 4.45 AU with an orbital inclination of 3o.4 and orbital eccentricity of 0.87. The object passed perihelion on August 12.

 

click to enlarge
 

These results are preliminary, although probably close to the eventual values. The standard way of reconstructing meteor trajectories (the intersecting planes method) which I used here works fine for regular meteors, but for meteors with these extremely long, very shallow trajectories, the trajectory can get a  non-negligible curvature due to gravity. This effect is small, but I nevertheless want to re-analyze the trajectory the coming month, splitting it up in parts, so that I can account for this curvature. It will be interesting to see what the effect is on the position of perigee (the point of closest approach to earth), and on the radiant position.

Added note:  

Jelle Assink of the Royal Dutch Meteorological Institute (KNMI) reported on Twitter that infrasound from this fireball has been detected.

(a few small edits and additions have been made after this blogpost was originally posted)


Acknowledgement: 

I thank Paul Haworth, Cees Bassa, Klaas Jobse, Marco Verstraaten, Jaap van 't Leven and Felix Bettonvil for making their imagery available for analysis.


Sunday, 20 September 2020

Observing the mysterious "Object A" (2020-063G), left in orbit by China's 'Spaceplane'

 

Earlier this month I wrote a post about China's brand new, recently launched and landed 'Reusable Test Spacecraft' (2020-063A), probably a 'Spaceplane' similar to the US  X-37B. It was launched on September 4 from Jiuquan, and landed on September 6 at Lop Nor, after two days on orbit (see a previous post).

As I noted near the end of that post, it left something in orbit: an object of unknown character, which the US Military tracking network now calls 'Object A' (a bit confusing I think, as the COSPAR code is 2020-063G - so I'd called it 'Object G'). It is in a 347 x 331 km orbit.

click diagram to enlarge

This does not appear to be just a piece of debris - e.g. some discarded cover. Radio observers discovered that it sends a signal in the L-band near 2280 MHz, something debris doesn't do. So, this appears to be an interesting object that had or has some function, including a radio data signal downlink. It does not appear to have manoeuvered so far, and if it is tumbling (see below) it isn't likely to do so..

I initially thought that it might be a cubesat, but it appears to be rather large for that. At maximum brightness it reaches magnitude +4, i.e. it is visible to the naked eye. Speculation is that it is either an inspector satellite used to inspect the outside of the Chinese spaceplane before landing: or maybe some jettisoned support module. The ejection from the 'Reusable Test Spacecraft' appears to have taken place some two revolutions before landing, or perhaps even earlier (see brief analysis at the bottom of a previous post).

I filmed the object this morning with the WATEC 902H equipped with a 1.8/50 mm lens - see the movie above. The mysterious object showed slow but marked brightness variations, between magnitude +4 and invisible (= fainter than +7). This confirms reports by radio observers of periodic fading in the signal.

Below is the brightness curve that I extracted from my video, using LiMovie. I was handtracking the object, and halfway lost it for over half a minute when it became too faint for the WATEC 902H (equipped with a 1.8/50 mm lens): hence the half-minute gap in the curve. The other, smaller gaps in the curve are moments that I repositioned the camera. One of these days, I really have to start using a motorized mount tracking on the satellite for this kind of endeavours.

The curve shows two brightness peaks, and two major fading episodes. Peak-to-peak period is about 80 seconds, so if this is due to a tumble, it is a slow tumble.

click diagram to enlarge

When I first picked it up (it had just come out of earth shadow), it initially was very bright and steady (see the movie in top of this post). But then it started to get fainter, untill I momentarily lost it. When I picked it up again, it was becoming brighter again, and after a slow peak, it faded again to invisibility. The fades are faster than the brightening phase and brightest phase.

Thursday, 17 September 2020

The structure of Space (2): formation of a geosynchronous ring


 

A year ago, I published a post on 'The structure of Space'. In that contribution, I discussed structure in orbital element space, identifying spacecraft orbital 'families'. But how about 'structure' in a more traditional spatial sense?

A few days ago, I had some light Twitter-banter with the fantastic Alice Gorman ( aka 'Dr Spacejunk'). She asked

"why is it that space junk has not turned into rings around Earth, just like Saturn or Neptune? Kessler and Cour-Palais (1978) argued it was because the smaller particles were removed by atmospheric drag before enough mass could accumulate"

I pointed out that our Earth by all means does have an artificial ring of space debris and functional payloads: the geosynchronous ring. Which, as we will see, is more of a geosynchronous torus, actually. It is not so dense (yet) with objects as the rings of Saturn or Neptune (but give it time!), but it will be long lasting, outliving us humans.

This sparked a few creative days (I had to get my mind off a few things). I wrote a small .NET application that calculates ECEF coordinates of satellites and fed it with all objects from the CSpOC and our classified catalogues: 20058 tracked objects ranging from operational payloads to small debris particles. Next, I used QGIS to make plots of these ECEF coordinates (I know: I often tend to use software for things other than what they originally were developed for).

The results are in the images below: each image pair shows a polar view at left looking down at the north pole, and a side view at right, looking in the equatorial plane. The plots are for 15 September 2020 at 0h UT.

Here is a zoomed in view, showing the objects in lower orbits (left a polar view, right an equatorial view: thickmarks are in units of 2000 km):

Click image to enlarge

As an aside: notice the small circular area with lower object density at the pole, rimmed by a higher density ring (it is also visible in the wider plot below). This is due to the fact that objects in polar orbits tend to have orbital inclinations  a few degrees higher than 90 degrees: notably so to achieve a sun-synchronous orbit (typical orbital inclinations for such orbits are 97-98 degrees).

In the wider, zoomed out plots below that show the higher objects, you can clearly see the geosynchronous ring at ~35785 km in the polar view at left (thickmarks are in units of 10 000 km). It is made up of geostationary and geosynchronous satellites and debris.These are the satellites that bring you satellite television, satellite telephony, and that bring SIGINT and early warning data to the militaries of various governments. The objects inside the outer ring are objects in MEO (e.g. GPS satellites) and GTO (old rocket stages form launches to GEO and other debris):

Click image to enlarge

If you look at the equatorial view at right, you'll note that the geosynchronous 'ring' is actually more a geosynchronous torus. You see a thin line of actual geostationary objects (mostly operational or untill recently operational payloads) in the Earth's equatorial plane with orbital inclination ~0: and a wider band of geosynchronous objects, that have orbital inclinations between roughly 0 and 15 degrees (both operational payloads, defunct payloads including some in a graveyard orbit, and debris).

The latter torus is situated slightly slanted with respect to the Earth's equatorial plane. The orientation of this slant shows a daily cycle, causing a funny 'wave' like behaviour of these satellites over a full day, when we look at their geographic positions in the equatorial plane, as can be seen in this mesmerizing animation that I created:

click animated map to enlarge

In this animation, the colours represent the object density plotted as a kernel density heatmap: red areas are most dense with objects. The small white dots are the actual geosynchronous satellites (plotted for 15 September 2020). There is a thin line of objects at latitude ~0 that are truely geostationary due to stationkeeping: these hardly move. But the geosynchronous objects with inclinations > 0 show a wave-like pattern of movement over the day!

This movement is a tidal effect, created by solilunar perturbations: gravitational perturbations by the sun and (notably) the moon. These tug on these objects a little, so unless you do frequent stationkeeping manoeuvers that keep the orbital inclination near zero, these objects will see their orbital inclinations start to oscillate, between 0 and 15 degrees over a period of roughly 54 years (53-55 years: it depends on the exact altitude of the satellite). This causes the torus, and the slant. The daily 'wave' (wobble) of this torus is caused by a combination of these tidal effects and the daily rotation of the earth, similar to ocean tides.

I have visualized the discussed ~54-year oscillation by plotting the evolution of the orbital inclination against time of Intelsat 1 (1965-028A), the first commercial geostationary satellite that was launched in 1965. It has just completed a full cycle of this moon-and-sun induced oscillation since it's launch:

click diagram to enlarge

In the absense of active stationkeeping (operational payloads make stationkeeping-manoeuvers roughly each two weeks), there is an oscillation in longitude too, induced by the J2 resonance: due to the uneven mass distribution of the Earth (it isn't a perfect sphere but rather a slightly deformed, bulgy egg), geosynchronous objects without stationkeeping start to oscillate in longitude around one of two "stable" points. These points are at ~75 E and ~105 W longitude: the white crosses in the plot below.

click map to enlarge


This oscillation in longitude about one of the stable points is well visible in 55 years of Intelsat 1 orbital data. Below I have plotted the position of the satellite in longitude from 1965 to 2020. You clearly see it oscillate around one of the equilibrium points (the 105 W point, marked by the dashed line in the diagram), with a periodicity of about 3.1 years:

Click diagram to enlarge


Over time this effect will also tend to concentrate space debris at geosynchronous altitudes around these two points. This effect can be seen in the kernel density heatmap (the coloured band) above the diagram, and in the histogram below (two peaks in the distribution, near the first equilibrium point at 75 E and the second equilibrium point near 255 E = 105 W) although it is to some extend masked by a preference of operational payloads to be at the longitudes of either Asia or the USA, where the biggest commercial markets for satellite tv and satellite telephony are.

click diagram to enlarge

Objects at geosynchronous altitude will not decay in millions to perhaps billions of years to come: so the geostationary ring that formed since 1965 will be here to stay, well after we humans are gone. It will be one of the clearest, longest lasting archaeological signatures of the Anthropocene.

Of course the character of the ring will change. Breakups will fragment the larger objects, decreasing the particle size distribution and increasing the number of objects in the ring even when human launches have stopped. Solar Radiation Pressure will more strongly act on smaller particles, so orbital eccentricities (and presumably also inclinations) will change, causing the ring to get more diffuse in time. I do not know of really long-term simulations (the longest I have been able to find was over a mere 200 years period), so cannot put exact figures on this.

The geosynchronous ring is a remarkable form of planetary change: untill quite recently our planet did not have a ring, but now it has, and it is completely artificial. It formed in a short time. In the animation below, I have broken down the current distribution of objects in the ring (for 15 September 2020) into launch timeframes of 5 years, starting 1960 (i.e. just before the first geostationary launches started) and ending at present:

This shows the gradual, but in terms of geological time nevertheless extremely rapid formation of our planet's artificial ring over the past 55 years. This ring will be a long-lasting, visible human footprint in space, probably outlasting all others (including footprints on the moon, that will be wiped out over time by meteorite impacts).

If you have a telescope or a good camera, you can see this ring of objects every night. Here is a photograph of a small part of it:

Click image to enlarge

Friday, 11 September 2020

Important update of my SkyTrack software [UPDATED]

 


In the context of the probable landing site of the recent Chinese Experimental Spacecraft (see previous post), I discovered a serious bug in my SkyTrack software.

As it turns out, when your chosen observing site has an altitude well over MSL, the sky positions in RA/DEC and AZIMUTH/ELEV are significantly off in version 2.5. I had not noticed this before, as my own observing location is at MSL.

The reason for this error is stupid: the SGP4 DLL needs an altitude in km, while in my code I failed to convert the site altitude from meters to kilometers....hence, a site at 995 meter was treated as if was a site at 995 km...oopsie!

Anyway: I have corrected the error and the new version 2.6 is now for download at my software website.

 

UPDATE 12 Sep 2020:

A second important bug fix was made, leading to version 2.7 now downloadable.

It corrects an error where, when adding a new site, southern latitudes and western longitudes were incorrectly written to the database...

 

Starting version 2.6, I also included a few lines of code that should solve another problem and forces the software to recognize the dot as the decimal separator during runtime of the program, no matter what your regional windows setting is. This likewise avoids output errors.

For those unfamiliar with the software, there is an earlier blogpost detailing it.

In short, the software takes as input a set of orbital elements in TLE-format, and allows you to calculate, for a given custom time interval in custom time steps:

- The latitude, longitude and altitude of the satellite;

- An indication whether it is sun-illuminated or not;

- the Right Ascension (RA) and Declination in the sky, for your observing site;

- the Azimuth and Elevation in the sky, for your observing site;

- the Range (in km) to your observing site;

...and optionally also:

- a KML file of the trajectory that you can load into Google Earth;

- the Doppler-corrected radio frequency (for a given central frequency);

- EFG (ECEF) x, y, z coordinates of the satellite;

- format the data as .csv so it can easily be imported into mapping applications like QGIS.

- choice between various output formats and Datums for the Lat/Lon and RA/DEC data

The software also has options to restrict the output to a certain minimum elevation as sen from your observing site, and/or output only when the satellite is sun-illuminated (and hence visible).


Saturday, 5 September 2020

China launches a 'Reusable Experimental Spacecraft' - a Space Plane? [UPDATED MULTIPLE TIMES]


Early September 2020, the space tracking community was in nervous anticipation of a rather mysterious Chinese launch. Amidst tight security measures, a Changzeng-2F (CZ-2F) rocket was readied at SLS-1 of Jiuquan's Launch Area 4. Chinese tracking ships were taking up positions near South America and in the Arabian Sea. Two NOTAM's appeared suggesting a launch between 5:20 and 6:00 UT on September 4. Something was afoot! Speculation was, that this was the long anticipated inaugural launch of a robottic Space Plane, a version of the Shenlong, China's answer to the American Air Force's X-37B robottic Space Plane.

Then, on September 4th, the Chinese news agency Xinhua published a very brief news item announcing that a CZ-2F from Jiuquan had launched a 'Reusable Experimental Spacecraft' earlier that day. 

The bulletin was scarce in information but stated that "after a period of in-orbit operation, the spacecraft will return to the scheduled landing site in China. It will test reusable technologies during its flight, providing technological support for the peaceful use of space".

No further details were given on launch time, orbit or character of the spacecraft. The description of the spacecraft is a bit ambiguous. Instead of a space plane, a 'reusable spacecraft' could in theory also be some sort of capsule (e.g. like the SpaceX Dragon): but most analysts think this indeed refers to the long rumoured space plane, China's answer to the US X-37B.

Pre-launch, and based on the positions of the hazard zones from the two NOTAM's, I calculated a launch into an orbital inclination of ~45 degrees, incidentally similar to the orbital inclination of the X-37B OTV 6 mission currently on-orbit. What's more, the launch window given (the NOTAM windows were from 5:23 to 6:05 UT) indicated the possibility of a launch into the orbital plane of OTV 6! The orbital plane of OTV 6 passed over Jiuquan at 6:00 UT - near the end of the launch window.

I published the following expected track for a launch into a 45 degree inclined orbit (which we now know is wrong):

Initial pre-launch trajectory guess. Click map to enlarge


When later that day the first orbital elements by the US military tracking network appeared on the CSpOC portal, it turned out that the orbital inclination was not ~45 degrees, but 50.2 degrees, 5 degrees higher than I anticipated. The reason for the mismatch, is that the rocket apparently did a dog-leg manoeuvre during ascend. This is very clear when we plot the orbital ground track in relation to the launch site and hazard zones from the two NOTAM's: it passes obliquely between them rather than lining up.

Actual orbital track. Click map to enlarge

 A 'dog-leg' manoeuvre is usually done for safety reasons, to avoid overflying a particular area downrange (e.g. a city or a foreign nation), but can also be done to insert the spacecraft into an orbital inclination that otherwise cannot be reached from the launch site. The latter is however not the case here - [editted] the orbital inclination is higher than the launch site latitude (you cannot reach an orbital inclination that is lower than your launch site latitude without a dog-leg, but higher you can.). So the reason must be range safety.

It is clear that the launch occurred well outside the NOTAM time window (why, is not clear). My analysis, based on a proximity analysis using the orbits of the spacecraft, the upper stage of the CZ-2F rocket, and that of four engine covers ejected upon spacecraft separation, indicate spacecraft separation and insertion into orbit around 7:41 UT on September 4th, over the Chinese coast with the orbital plane lining up with Jiuquan (see image below which depicts the orbital position at orbit insertion). The launch itself then should have occured some 8-10 minutes earlier i.e. around 7:30 UT, give or take a few minutes.

Moment of orbital insertion. click to enlarge
 

The spacecraft was inserted into a 50.2 degree inclined, initially 332 x 348 km orbit. During the hours after launch, the spacecraft made small orbital manoeuvres (see diagram below). At the time of writing (5 September 20:45 UT) it is in a 331 x 347 km orbit.

click diagram to enlarge

The later than initially expected launch time and, through a dog-leg manoeuvre, insertion into a 50.2 degree inclined orbit moved the orbital plane away from that of the X-37B OTV 6, although the two orbital planes are still near. Igor Lissov has pointed out some resemblance to the orbital plane of another US classified payload, USA 276, which has a similar orbital inclination to the Chinese spacecraft (but 50 km higher orbital altitude). The RAAN difference is 8 degrees:

click to enlarge

Based on the current orbits of all three spacecraft, there will be no close approaches of the Chinese spacecraft to either of these classified US payloads over the coming two weeks.

OTV 6 is currently in a 383 x 391, 45.0 degree inclined orbit. The difference in RAAN with respect to the Chinese spacecraft is 13.4 degrees, with a 5.2 degree difference in inclination and about 40-50 km difference in orbital altitude.

USA 276, the mysterious spacecraft that made a close approach to the ISS in May 2017 (see my July 2017 article in The Space Review), is currently in a 397 x 395, 50.0 degree inclined orbit. The difference in RAAN with respect to the Chinese spacecraft is 7.9 degrees, with a 0.2 degree difference in inclination and about 50-60 km difference in orbital altitude.

The Chinese 'reusable' spacecraft was launched from SLS-1, one of two launch platforms at Launch Area 4 of the Jiuquan Space Launch Center. Below is a Copernicus Sentinel 2B image of the launch complex, taken on September 2nd, two days before the launch. The two launch platforms are indicated: the southernmost one is the platform used for this launch.

click image to enlarge


It will be interesting to see where the 'reusable spacecraft' will eventually land. One likely candidate is a military airfield, the Dingxin Test and Training Base, that is located some 75 km southwest of the launch site. I have indicated both the launch site (A) and the potential landing site (B) in the Copernicus Sentinel 2B image below. The second image gives a more detailed look on the airbase.

Click image to enlarge

 
Click image to enlarge

We have no clue how long the spacecraft will stay in orbit. It will be interesting to see when and where it lands.

The 'reusable spacecraft' has the CSpOC catalogue entry #46389 (COSPAR ID 2020-063A). The CZ-2F upper stage is object #46390 (2020-063B). The four ejected engine covers (with apogees in the 458 to 566 km range), have numbers 46391-46394 (2020-063A to 202-063F).


UPDATE 6 Sept 2020 8:45 UT:

Xinhua reports on Sept 6 that the spacecraft has landed after 2 days on-orbit. Depending on the landing site, landing should have been (based on orbital overpass) either around 1:55 UT at Lop Nor (an alternative landing site suggested), or 6:45 UT at Dingxin Airbase.

UPDATE 2, 9:30 UT:
As the Chinese version of the Xinhua bulletin dates to an hour after the first option (1:55 UT), it seems that the landing was near 1:55 UT near Lop Nur in the Taklamakan desert (HT to Jonathan McDowell).

UPDATE 3, 10:30 UT:
This is the potential landing site, a triangular arrangement of 5 km long landing strips in the Taklamakan Desert. The orbital track of the spacecraft passed some 42.5 km northwest of it around 1:54 UT, more or less parallel to what appears to be the main landing strip:

Click image to enlarge

Click image to enlarge

UPDATE  4, 14:00 UT:
This is an updated diagram of the orbital evolution over the test flight. It seems no large manoeuvers were tried during this flight.



Click diagram to enlarge

UPDATE 5, 16:00 UT:

Jonathan McDowell noted that a new object related to the launch has been catalogued, object 2020-063G, #46395. My analysis suggests it was ejected from the experimental spacecraft near 22:25 UT on the 5th, two revolutions before landing. It likely is a cubesat of some sort. It is in a  332 x 348 km, 50.2 degree inclined orbit. (Update 8 Sept: on Twitter, Bob Christy has suggested that it might be a small inspector satellite, used to inspect the outside of the experimental spacecraft prior to deorbit)