Delfi-C3 reentry forecast updates (periodically updated post)

 

[ Post last updated:  14 Nov 2023  12:45 UTC ]

In my October 25 blogpost I presented imagery of the iconic 3U cubesat Delfi-C³ (2008-021G) taken by my tracking camera. I also provided a reentry forecast in that post, that I updated several times.That reentry is currently (mid November 2023) very near.

I am now consolidating the reentry forecasts in this current, periodically updated blogpost.

While late October the reentry forecast was still shifting to a later date with each orbit update, that shift is now flattening out, but the forecast is still fluctuating. 

A geomagnetic storm that caused aurora at middle latitudes on Nov 5/6 has had a clear effect in speeding up orbital decay (the 'dip' can be seen in the digrams below). Over the weekend 11-12 November, solar activity was more mild than forecast, making the reentry forecast slowly shift to a later time with each orbital update.

My current "aftercast", based on a mid-November 13 orbit modelled in GMAT, is reentry on 13 November 2023, nominally near 20:39h UTC +- 1.5 hours (please note the uncertainty interval!), i.e. between 19 - 22 UTC (and likely  between 20 - 21 UTC)

A SatEvo/SatAna analysis results in a very similar, if slightly earlier, time (nominally 19:34 +- 1.5h UTC). I do not expect it survived to November 14.

The orbit determination on which these 'aftercasts' are based, is from about 3 orbital revolutions before the forecasted reentry moment. This orbit can be of bad quality, as in these final stages, orbit determination is tricky.

Here is how the reentry forecast has been developing so far (note the sudden downward developing trend due to the Nov 5/6 geomagnetic storm):

click diagrams to enlarge

 

This is probably the last reentry forecast update (or rather "aftercast" by now), as I do not expect new orbital elements to be released between this update and the reentry

(Note: forecast data in tabular form are at the bottom of this post)

This is the Delfi-C³ ground-track over the current uncertainty interval (spanning two orbital revolutions) in the forecast:

 

click map to enlarge

These reentry predictions are based on a tumbling satellite with, due to the tumbling, an average drag surface of about 60% of the maximum drag surface. Previous experience with modelling reentries in GMAT has shown this to be a reasonable value for a tumbling object. 

What makes these reentry forecasts challenging, and creates the large uncertainties in the reentry position is a combination of things. One is the, even at short timescales, varying solar activity and it's influence on the upper atmosphere, which cannot be well predicted or captured by the model. Second, during the last orbits just before reentry, all kind of gas flow mechanisms around the spacecraft are taking place, which alter tyhe cdrag it expriences. Moreover, in this final stage where the spacecraft meets a more thicker resistance of the upper atmosphere, it sometimes auto-stabilises itself in a least-drag orientation, prolonging survival slightly. Last but not least: in the last moments of the spacecraft's life, when it is in a very low, fast changing orbit, orbit determination becomes difficult, affecting tehe quality of the last orbital elements available for the forecast.

I do not expect a TIP to be issued for this object. TLE updates might end a few hours before the actual reentry, after which CSpOC issues an 'administrative decay'.

Delfi-C³ 's orbit had decayed to below 187 x 177 km by mid 13 Nov 2023, and the cubesat was coming down increasingly fast, as can be seen in the diagrams below (the orbit was dropping by almost 100 km/day mid 13 Nov 2023):

 

click diagrams to enlarge

click diagram to enlarge

Note that Delfi-C³ is very small and lightweight (2.2 kg and 30 x 10 x 10 cm) and the reentry will have been completely harmless. The friction with the molecules in the atmosphere will heat up the spacecraft during its final moments, untill it burns up completely, at altitudes above 50 km. The current ground-track where it can come down, is almost completely over Ocean.

The operators of Delfi-C³ have put out a call to radio amateurs to try to receive and decode telemetry from the cubesat. Software to decode is provided here. The goal is to try to follow Delfi-C³ and get telemetry as close to reentry as possible.

Note that Delfi-C³ only sends telemetry when it is in sunlight, and not continuously as after 15 years the system is showing issues. The frequency is 145.870 MHz, it is sending 1200 Bd BPSK packages. See also here. 

[EDIT:  as off 11 november, the cubesat seems to have shifted to a backup frequency near 145.934 MHz, as can be seen in this spectogram from my detection in the morning of November 11. The 145.870 MHz frequency is also still intermittently active. So pay attention to both frequencies]

click spectrogram to enlarge

[end of edit]

On the morning  of  Nov 8, during the 7:43 UTC pass, I received thise radio signal of Delfi-C3 from Leiden, the Netherlands (but could not decode the signal), clearly a bit early on the then available TLE:

click image to enlarge

The "stepped" effect is due to attempts to correct the Doppler shift. That Doppler shift (the "s"-shape in frequency due to the Doppler effect in the signal) can be very nicely seen in this spectogram from the same pass as received by my colleagues at Delft University of Technology (image courtesy Bart Root, TU Delft):

click image to enlarge. Image courtesy Bart Root, TU Delft

 

Radio signals from the cubesat were also received by me and the TU Delft station on later dates, most recently in the morning of November 13th during the 7:24 UTC pass:

Nov 13 ~7:24 UTC radio spectrogram from Leiden. Click image to enlarge

Delfi-C³ is a 3U cubesat developed and built at Delft Technical University in the Netherlands, and launched 15 years ago, in 2008.

More on Delfi-C³ on the website of Delft Technical University. There is also a nice background article on it's 15-year anniversary here.

The last (and only!) visual image of Delfi-C3 on-orbit, taken by me on 24 October 2023 from Leiden, the Netherlands, using a WATEC 902H2 Supreme and Samyang 2.0/135 mm lens at 25 fps (image is a frame-stack of 16 frames: the faint trail lower right is Delfi-C3 moving through the field of view. See also blogpost here which also features some video footage):

 

TABLE:  Forecast development in tabular form (most recent one at bottom).
All dates and times are in UTC. Quoted times are nominal times, please take into account the uncertainty intervals that go with them!

orbit date         orbit epoch     reentry forecast + uncertainty      
08 okt 2023 13:52  23281.57810544  05 nov 2023 02:23  ±  8.3  day
09 okt 2023 14:28  23282.60344413  05 nov 2023 08:17  ±  8.0  day
10 okt 2023 19:41  23283.82047902  05 nov 2023 11:00  ±  7.7  day
12 okt 2023 00:53  23285.03692402  05 nov 2023 20:20  ±  7.4  day
13 okt 2023 01:27  23286.06083878  06 nov 2023 18:43  ±  7.4  day
14 okt 2023 00:29  23287.02034889  06 nov 2023 18:53  ±  7.1  day
15 okt 2023 08:42  23288.36296159  07 nov 2023 00:59  ±  6.8  day
16 okt 2023 00:02  23289.00204702  07 nov 2023 04:44  ±  6.7  day
16 okt 2023 15:23  23289.64097529  08 nov 2023 02:01  ±  6.7  day
17 okt 2023 18:58  23290.79063916  08 nov 2023 12:14  ±  6.5  day
18 okt 2023 19:29  23291.81212343  08 nov 2023 21:43  ±  6.3  day
20 okt 2023 00:35  23293.02450124  09 nov 2023 16:03  ±  6.2  day
21 okt 2023 01:04  23294.04489630  09 nov 2023 19:49  ±  5.9  day
21 okt 2023 19:26  23294.80984121  09 nov 2023 22:19  ±  5.7  day
22 okt 2023 19:54  23295.82928392  09 nov 2023 23:43  ±  5.4  day
24 okt 2023 07:03  23297.29389307  10 nov 2023 23:54  ±  5.3  day
26 okt 2023 00:17  23299.01200402  11 nov 2023 11:29  ±  4.9  day
27 okt 2023 00:42  23300.02946319  11 nov 2023 12:23  ±  4.6  day
28 okt 2023 01:06  23301.04628230  11 nov 2023 16:02  ±  4.4  day
28 okt 2023 19:24  23301.80847586  11 nov 2023 18:46  ±  4.2  day
30 okt 2023 00:20  23303.01441157  12 nov 2023 09:54  ±  4.0  day
31 okt 2023 00:41  23304.02910990  12 nov 2023 13:04  ±  3.8  day
01 nov 2023 01:02  23305.04306068  12 nov 2023 17:28  ±  3.5  day
02 nov 2023 11:58  23306.49918974  12 nov 2023 17:44  ±  3.1  day
03 nov 2023 07:42  23307.32139835  12 nov 2023 23:36  ±  2.9  day
04 nov 2023 07:58  23308.33247480  12 nov 2023 19:20  ±  2.5  day
05 nov 2023 00:38  23309.02698061  12 nov 2023 21:03  ±  2.4  day
06 nov 2023 00:51  23310.03600547  12 nov 2023 05:15  ±  1.9  day
07 nov 2023 01:02  23311.04321962  12 nov 2023 09:23  ±  1.6  day
07 nov 2023 13:06  23311.54617034  12 nov 2023 14:38  ±  1.5  day
07 nov 2023 14:36  23311.60900895  12 nov 2023 14:25  ±  1.5  day
08 nov 2023 01:10  23312.04868443  12 nov 2023 15:48  ±  1.4  day
08 nov 2023 13:13  23312.55073768  12 nov 2023 19:28  ±  1.3  day
08 nov 2023 19:14  23312.80157938  12 nov 2023 20:14  ±  1.2  day
08 nov 2023 20:44  23312.86427030  12 nov 2023 20:32  ±  1.2  day
09 nov 2023 01:15  23313.05229412  12 nov 2023 21:16  ±  1.2  day
09 nov 2023 13:16  23313.55332040  12 nov 2023 20:49  ±  1.0  day
09 nov 2023 14:46  23313.61590941  12 nov 2023 20:54  ±  1.0  day
09 nov 2023 19:17  23313.80362555  12 nov 2023 21:54  ±  22.4  hr
10 nov 2023 01:17  23314.05377944  12 nov 2023 23:07  ±  20.9  hr
10 nov 2023 14:47  23314.61604116  13 nov 2023 01:14  ±  17.5  hr
10 nov 2023 20:46  23314.86565574  13 nov 2023 01:32  ±  15.8  hr
11 nov 2023 01:15  23315.05274319  13 nov 2023 02:37  ±  14.8  hr
11 nov 2023 13:13  23315.55109903  13 nov 2023 06:40  ±  12.4  hr
11 nov 2023 19:11  23315.79995400  13 nov 2023 08:42  ±  11.3  hr
12 nov 2023 01:09  23316.04856854  13 nov 2023 10:21  ±  10.0  hr
12 nov 2023 14:34  23316.60695182  13 nov 2023 14:53  ±   7.3  hr
13 nov 2023 00:57  23317.03998349  13 nov 2023 17:11  ±   4.9  hr
13 nov 2023 11:18  23317.47133062  13 nov 2023 19:55  ±   2.6  hr
13 nov 2023 12:47  23317.53274184  13 nov 2023 20:06  ±   2.2  hr

FINAL 'aftercast':
13 nov 2023 15:53  23317.65534723  13 nov 2023 20:39  ±   1.5  hr

A Goodbye to Delfi-C3

Delfi-C3 tracklet on a stack of 16 video frames, 24 Oct 2023

 (note: new reentry forecasts are now published in a separate dedicated blogpost)

Earlier this year, my TU Delft colleague Stefano Speretta asked me if I could try to I imaged a pass of the TU Delft-built 3U cubesat Delfi-C³ (2008-021G). 

It next took a long time due to initially unfavourable observing geometries and - when the observing geometries got better - the Dutch weather, but I finally managed to successfuly image it in late evening twilight of 24 October 2023. 

Above is a stack of 16 video frames showing the tracklet created by the cubesat; below is the actual video footage, shot with a WATEC 902H2 Supreme camera and Samyang 2.0/135 mm lens at 25 fps (the object is very faint in the footage, due to it being very small in size):

 

Delfi-C³ (2008-021G) is a 3U cubesat and was the first cubesat built in the Netherlands. It was launched on 28 April 2008 from Satish Dawan in India on a PSLV rocket, as part of a rideshare mission.

It was built by students of Delft Technical University (my current employer) as the first in what was to become a line of Dutch-designed-and-built cube- and pocketsats. It carried at that time experimental technology (autonomous star sensors and thin-film solar panels) and an amateur radio responder. More information on the cubesat, its mission and the technology onboard can be found at the TU Delft website.

Although no longer operational, there is occasionally still radio telemetry received from the cubesat by our TU Delft Rooftab Radio lab.

 

Delfi-C³ in stowed condition (image: TU Delft)

Delfi-C³in deployed condition (image: TU Delft)

Fifteen years after launch, it is time to say Goodbye this very successful cubesat. It has less than half a month to live.

 

[post NO LONGER UPDATED below. Instead refer to this new dedicated post here for new reentry forecast updates]

Initially launched into a 615 x 635 km, 98.0 inclined orbit, the orbit has now decayed to 321 x 324 km (status as of 3 Nov 2023), and the cubesat is coming down increasingly fast, as can be seen in the diagrams below (currently, the orbit is dropping by 4 km/day (status 3 Nov 2023)):

click diagrams to enlarge

click diagram to enlarge

 

Delfi-C³ will probably reenter into the atmosphere and burn up somewhere mid-November 2023 (depending on how solar activity develops over November).

Here is the evolution of my GMAT reentry forecast so far (ignore the error bars and quoted  reentry date uncertainty for now, as this far before reentry they still have little meaning, due to the uncertainty in future solar activity):

click diagram to enlarge

The initial shift of the forecast over time towards a progressively later date is slowing down. My best guess at this moment (3 Nov2023) is reentry mid-November, around 12-14 November 2023, plus-minus a few days.

I will update this figure over the coming days and weeks, as the reentry forecast develops. 

New reentry forecasts are now published in a separate dedicated blogpost.

I do not expect a TIP to be issued for this object. Recent experience shows that TLE updates will probably cease some 2-3 days before the actual reentry, after which CSpOC issues an 'administrative decay'.

Delfi-C³ is very small and the reentry will be completely harmless, with the cubesat burning up completely.

Optically observing the RNLAF's 6U cubesats BRIK-II, HUYGENS and BIRKELAND

 

WATEC 902H2 Supreme camera with Samyang 2.0/135 mm lens and GPS time inserter

The Royal Netherlands Air Force (RNLAF) launched its first satellite, the cubesat BRIK-II (2021-058F), two years ago as part of the Virgin Orbit Tubular Bells rideshare on 30 June 2021 (see an earlier post here).

Two more satellites, HUYGENS (2023-001CN) and BIRKELAND (2023-001G) were recently launched for the RNLAF as part of the SpaceX Transporter 6 rideshare on 3 January 2023. These two satellites, which move in the same orbital plane, are co-owned by the RNLAF and the Norwegian Ministry of Defense.

The satellites are 6U cubesats, with the bus measuring 10 x 20 x 30 cm (roughly the size of a shoebox). Huygens and Birkeland have unfolding solar panels expanding their size to about 30 x 60 cm.

 

Brik-II during assembly and testing (image: Netherlands Ministry of Defense)

 

Rendering of Huygens (image: Nanoavionics)

 

orbits of the Brik-II, Huyugens and Birkeland cubesats

 

Over the past two weeks I have imaged all three satellites from Leiden - in the case of  Huygens and Birkeland even on multiple nights - using my WATEC 902H2 Supreme camera fitted with a 2.0/135 mm light telelens. 

Brik-II remained very faint during the one pass I imaged, but Huygens and Birkeland were surprisingly easy to see, as can be seen in the framestacks and video's further down in this blogpost.

 

BRIK-II

Below are a framestack and a short video of the March 30 Brik-II detection. I have processed the video for visibility (which also increased the noise) as the cubesat was very faint: look for a very faint, fast object coming from the upper left corner.

I had tried to image the satellite earlier on several occasions the past two years, but this was the first time I had a positive detection.

 

Brik-II, framestack from footage taken March 30, 2023

video footage of Brik-II (very faint!)

 

HUYGENS and BIRKELAND

Below are framestacks and video footage of passes of Huygens and Birkeland taken on March 30, April 4 and April 8, 2023. These two cubesats were much more readily visible than BRIK-II and you'll have no problem seeing them in the footage

The video footage of Huygens is from April 4, of Birkeland from April 8. They were (on all three nights involved) clearly better visible than Brik-II was on March 30. This is partly due to a better observing geometry, but it does seem that Huygens and Birkeland are really intrinsically brighter than Brik-II. They reached magnitude +7.5 to +8.

First, imagery - framestacks and brief video footage - of Huygens (2023-001CN) obtained on 30 March and 4 April, 2023:

Huygens on March 30,2023 (framestack)

Huygens on April 4, 2023 (framestack)

 video footage of Huygens on April 4, 2023

 

Next, imagery - a framestack, and a longer video - of Birkeland (2023-001G) obtained on 8 April 2023. The bright object initially seen passing in the upper left corner is a Starlink satellite (Starlink-5226): Birkeland is the fainter object coming from bottom right:

Birkeland on April 8, 2023 (frame stack)

 

 video footage (longer video) of Birkeland on 8 April 2023

 

Equipment

All the imagery was captured with a WATEC 902H2 Supreme low-light-level cctv camera fitted with a Samyang 2.0/135 mm lens, filming at 25 frames per second. Accurate timing of the video frames was provided with a BlackBoxCamera GPSBOXSPRITE-2 GPS time-inserter.

The system delivers an astrometric accuracy of about 15 arcseconds. The FOV is about 2.7 x 2.0 degrees. The footage was shot from my home in the center of Leiden, the Netherlands (52.154 N, 4.491 E).

The image below shows the equipment in question. The box at left is the GPS time inserter. The PAL video feed from the WATEC camera goes from the camera into the time inserter, which imprints each individual videoframe with a millisecond-accuracy time derived from GPS signals. After passing through the time inserter the video feed is going to a digitization dongle, and is next recorded on a laptop.

WATEC 902H2 Supreme camera with Samyang 2.0/135 mm lens and GPS time inserter

 

I used my observations to provide these orbit updates for Huygens and Birkeland:

HUYGENS
1 55093U 23001C   23098.81960162 0.00006982  00000-0  37378-3 0    02
2 55093  97.4857 159.4790 0014652 237.3630 122.6188 15.14989127    06

rms 0.004 deg   arc 30.85 Mar - 8.83 Apr UTC


BIRKELAND
1 55015U 23001G   23098.83187223 0.00009789  00000-0  53865-3 0    04
2 55015  97.4960 159.3843 0009401 256.5788 103.4395 15.14067850    03

rms 0.003 deg   arc 4.88 - 8.84 Apr UTC

 

These observations have wet my appetite to try to image more cubesats. The observations also underline (as we recently did in a conference publication as well) the power of relatively small but sensitive equipment. You really don't need a big telescope to track cubesats.

More on these satellites

With Brik-II, Huygens and Birkeland, the RNLAF is now entering active operations in the Space Domain.

Huygens and Birkeland are named after two iconic scientists, the Dutch Christiaan Huygens (1629-1695) and the Norwegian Kristian Birkeland (1867-1917). They were developed as part of the joint Milspace-2 program of the Dutch and Norwegian Ministries of Defense.

The two satellites operate as a pair, in the same 97.5 degree inclined orbital plane, Huygens currently in a 531 x 511 km orbit, Birkeland currently in a 530 x 517 km orbit. 

Their primary mission is ELINT: the geolocation and fingerprinting of Radar emissions. The two satellites are also used for experiments with formation flying.

Huygens and Birkeland orbit

Brik-II is named after Brik, the very first aircraft of a forerunner of the RNLAF, the "Luchtvaartafdeling" of the Royal Dutch Army, back in 1913. 

In Dutch, the word "brik" has several meanings: it is Dutch for "brick", as well as a slang name for a means of transportation (a cart or a car), in the latter case usually with the added connotation of it being somewhat decrepit.

The satellite is in a 60.7 degree inclined, 515 x 466 km orbit. Its experimental mission includes ELINT, communications, and Spaceweather monitoring. It was built for the Dutch Ministry of Defense by ISISpace in Delft. It is operated by the Defense Space Security Center in Breda.

 

"Brik", the first aircraft of the Dutch military, in 1913 (image Dutch Ministry of Defense)

Brik-II orbit

 

 

A surprisingly bright flare from a 6U Cubesat

​The 240 frames frame stack above, which is from the video below, shows the classified Japanese satellite IGS Optical 5 (2015-015A). But at 21:14:05.5 UT, somethings else moving nearly parallel to the satellite briefly flares up.

The flaring object in question, producing a flare of at least magnitude 0, is TYVAK 182A (also known as ELO Alpha), 2021-034D. This is a 6U cubesat. I am quite surprised to see such a bright flare from such a small object!

The video was taken from Leiden, the Netherlands, with a WATEC 902H2 Supreme fitted with a Samyang 1.4/35 mm lens.

First positive observations of the LED beacon of the NAPA-2 6U cubesat

 

On June 30, 2021, a Falcon 9 launched several cubesats in a rideshare launch called Transporter-2. One of the payloads was a 6U cubesat called NAPA-2. 

This cubesat was built by the Dutch company ISISpace in Delft (the same company that built Brik-II) for the Royal Thai Air Force. It is an IMINT satellite, carrying two small Earth observation camera's. It is in a 97.5 degree inclined sun-synchronous 520 x 540 km orbit with passes around local midnight and noon.

This is the NAPA-2 cubesat after assembly (image courtesy of ISISpace): the 6U cubesat measures about 10 x 20 x 30 cm.

image (c) ISISpace, used with permission.

NAPA-2 has an interesting novelty: it carries a beacon of 12 bright LED's that can be switched on and off by the satellite operators. 

It is an experiment to see if such a bright artificial lightsource on the satellite can aid in optically tracking it.

The past few days saw the commissioning of this feature. ISISpace had asked me whether I could try to image the LED beacon from Leiden. Attempts to image it were made on three nights. 

The first attempt, on August 24 using a 1.4/85 mm lens, was negative.

The second attempt was on August 25. The operators had reorientated the satellite such that the LED's were pointing at the groundstation. This attempt was marginally positive: it was seen but the satellite was extremely faint and barely visible and the trail was lost in the noise background in a frame stack.

A third attempt was made last night, in the early hours of 27 August. This time I used a more powerfull lens, the Samyang 2.0/135 mm. The camera was a WATEC 902H2 Supreme operating at 25 frames/s.

The result was a positive detection: the LED beacon of the satellite, although faint, was unambiguously imaged. The range to the satellite was 598 km during the observation. It was imaged around culmination at 61 degrees altitude in the east.

 

click to enlarge

 

Below is the video: the object, coming into the FOV from the right, is very faint, but visible. It disappears near the center of the image because the LED was switched off: the operators operated it is a "3-seconds-on, 1-second-off" mode last night.

Below is a framestack of 60 frames from the video (2.4 seconds of footage). A faint but unmistakable trail can be seen entering the FOV from the right: the LED beacon of NAPA-2! The bright star near the bottom of the image is 13 Persei.

Below is a negative image version of the same stack: and a positive version where I pushed the image such that the trail comes out better.

 

 

It should be noted that the cubesat was imaged in a part of it's trejactory where it was in Earth shadow: so all the light solely comes from the 12 LED's!

This is the LED array on the satellite (image courtesy of ISISPace):

image (c) ISISpace, used with permission.

Amazing that 12 LED's are visible from a distance of almost 600 km! 

The LED beacon does not operate continuously: it is only briefly switched on when passing over a tracking station (in this case, my observing location). It reaches an Rmag of about +10.

Below are the astrometric residuals relative to CSpOC elset 21239.30175625 (angles are in degrees, delta T in seconds), showing the good match:

     STA   YYday HH:MM:SS.sss   AZ     EL     XTRK     deltaT   Perr
( 1) 4353  21239 00:52:38.401   78.0   60.9   -0.02     0.02    0.023
( 2) 4353  21239 00:52:38.441   77.9   60.9   -0.02     0.04    0.033
( 3) 4353  21239 00:52:38.600   77.7   60.9   -0.02     0.03    0.030
( 4) 4353  21239 00:52:38.920   77.2   61.0   -0.02     0.03    0.025
( 5) 4353  21239 00:52:38.960   77.2   61.0   -0.02     0.06    0.044
( 6) 4353  21239 00:52:39.241   76.7   61.0   -0.02     0.03    0.031
( 7) 4353  21239 00:52:39.561   76.2   61.0   -0.02     0.03    0.031
( 8) 4353  21239 00:52:39.600   76.2   61.0   -0.02     0.05    0.044
( 9) 4353  21239 00:52:39.761   75.9   61.0   -0.02     0.03    0.025
(10) 4353  21239 00:52:39.801   75.9   61.0   -0.03     0.04    0.041

rms     0.03367

Imaging objects from the 'Tubular Bells' launch

image: Virgin Orbit

During the first days of July, I have tried to image objects from the June 30 Virgin Orbit 'Tubular Bells' launch, that launched a number of smallsats including Brik-II, the first Dutch military satellite (see earlier posts here and here).

I so far managed to unambiguously image three objects from the launch. One of these is probably the LauncherOne upper stage, the other two must be payloads.

On July 2nd, I imaged objects A and B, A using a 2.0/135 mm and B using a 1.4/85 mm lens on the WATEC 902H2 Supreme low light level video camera. B was very faint and barely visible.

On July 4th, I unambiguously imaged objects B and H using a 2.0/135 mm lens.

Object A is relatively bright and well ahead of the other objects. It is in a somewhat lower orbit: a 418 x 504 km orbit, whereas the other objects are in a 496 x 522 km orbit. So object 2021-058A almost certainly is the LauncherOne upper stage.

Below is video of the A-object, shot on July 2nd with the 2.0/135 mm lens. The bright star top left is Polaris. I could not see the other objects (passing about 30 minutes later): for passes to the north of me, the illumination angle is less favourable than for passes to the south of me.

 

The B and H objects are fainter, and only visible during passes to the south of me. The video below shows them, faint but unmistakenly, during a pass in evening twilight on July 4th (sun at only 7 degrees below the horizon, so the sky background was still quite bright).

 

A fourth object, Object C, was possibly seen on July 2nd when I watched the pass live on screen, but I could not see it anymore when inspecting the footage afterwards. 

Objects D, E, F and G were not seen, but on all imaged passes observing conditions were not perfect (on July 2, cirrus clouds were invading the FOV around the time of the objects D, E, F and G passing; while on July 4th the sky background was still very bright).

It is not clear which object is which at the moment, although I have reasons to believe that Brik-II must be either object D, E or F. I have some suspicion that objects B and H are part of STP27-VPA. [edit: see updates below: Object H was, but B is not).

UPDATE:

I obtained even better imagery of the two STORK objects (B and C) on July 17:

 

UPDATE 14 Jul 2021:

Object B actually appears to be one of the STORK satellites, based on Dopplerfitting of  radiosignals received at 401.1 MHz (and first detected by Alicja Musial in Poland). Object C also appears to be a STORK, based on Doppler fitting of the radio signal.. 

Objects D and E are now listed by CSpOC as CNCE3 and CNCE1, which are part of STP27-VPA.

Objects F, G and H then are Brik-II, Gunsmoke-J and Halo-NET (the latter two are part of STP27-VPA), with not certain which is which.

UPDATE 16 Jul 2021

Object F is now identified as Brik-II. Object H (One of the two objects I imaged on July 4) is now identified as Gunsmoke-J 2. 

As, from radio Doppler fitting, we know objects B and C are the STORKS (not yet identified as such by CSpOC), this means object G must be Halo-NET:

Object A    LauncherOne rb

Object B    Stork

Object C    Stork

Object D    CNCE3*

Object E    CNCE1*

Object F    Brik-II

Object G   Halo-NET*

Object H    Gunsmone-J 2*

* part of STP27-VPA

Bob Christy has pointed out that there might be a swap of the A and G designation in the future, to make the A designation a payload rather than the RB.

Navigational Warnings have appeared for the launch of the first Dutch military satellite, Brik-II [UPDATED]

 

artist impression of Brik-II in space (The Netherlands Ministry of Defense)

It was originally scheduled for launch in 2019, and postponed several times. But it now seems it will finally happen, on or near June 30: the launch of the Netherlands' first own military satellite, a 6U cubesat named 'Brik-II'.

The ministry of Defense of the Netherlands is partner in several already launched military satellites, but this will be the first satellite that is truely it's own. 

Brik-II was built by the Dutch aerospace company ISISPACE in cooperation with Delft Technical University, Oslo University and NLR and will be operated by the Royal Netherlands Air Force (RNLAF).

It is a small 6U cubesat (10 x 20 x 30 cm, weighing 10 kg) that contains equipment for communications relay, for Space Weather monitoring, and for ELINT (see my earlier post on Brik-II here).

 

image: The Netherlands Ministry. of Defense

 

Brik-II will be launched by Virgin Orbit as part of their  'Tubular Bells, part 1' mission that launches a number of small payloads: apart from Brik-II for the RNLAF, it will launch three or four (sources differ on the number [edit July 1: it were four payloads]) payloads for the US Dept. of Defense, and two payloads for the SatRevolution company.

The launch is an airborne launch, using a two-stage LauncherOne rocket launched from the Virgin Orbit Boeing 737 747-400 'Cosmic Girl' in front of the California coast.

images: Virgin Orbit

The launch was postponed several times, including this month, but Navigational Warnings have now appeared indicating an aimed launch date of 30 June (with backup dates July 1-5). 

The 3-hour launch window runs from 13:00-16:00 UT [edit: launch eventually was at 14:47 UT]. According to Virgin Orbit, the orbit aimed for is a 60-degree inclined circular orbit at ~500 km altitude. [edit] An infographic by the Royal Dutch Air Force mentions an orbital inclination of 60.7 degrees.

This is the navigational warning, NAVAREA XII 292/21:

 262041Z JUN 21
 NAVAREA XII 292/21(18,21).
 EASTERN NORTH PACIFIC.
 CALIFORNIA.
 1. HAZARDOUS OPERATIONS, ROCKET LAUNCHING
    301300Z TO 301600 JUN, ALTERNATE
    1300Z TO 1600Z DAILY 01 THRU 05 JUL
    IN AREAS BOUND BY:
    A. 33-36-44N 120-23-05W, 33-24-22N 120-17-14W,
       32-55-44N 119-55-39W, 30-38-19N 118-13-14W,
       28-24-39N 116-37-52W, 28-03-32N 116-17-09W,
       28-10-00N 116-05-44W, 28-24-41N 116-11-12W,
       29-07-31N 116-36-05W, 30-50-51N 117-46-19W,
       33-08-50N 119-32-16W, 33-33-26N 119-54-35W,
       33-45-27N 120-06-00W, 33-43-27N 120-16-02W,
       33-36-44N 120-23-05W.
    B. 23-13-25N 112-20-09W, 23-51-12N 113-00-01W,
       24-04-05N 113-17-34W, 24-00-35N 113-35-42W,
       23-49-04N 113-49-26W, 23-23-22N 113-46-59W,
       22-46-17N 113-39-25W, 22-01-49N 113-03-13W,
       21-54-11N 112-57-20W, 21-46-52N 112-49-48W,
       21-41-03N 112-38-21W, 21-40-45N 112-26-55W,
       21-44-25N 112-12-12W, 21-52-03N 112-03-22W,
       22-03-39N 111-58-08W, 22-13-42N 111-57-29W,
       22-26-28N 112-02-59W.
 2. CANCEL THIS MSG 051700Z JUL 21.

I have plotted the two areas on the map below, along with the trajectory for a 60-degree inclined ~500 km orbit, with times along the trajectory valid for launch at 13:00 UT, the start of the window (it will, however, probably launch a little after that: the second map is for a 60.7 degree inclined orbit and denotes times in minutes after launch):

click map to enlarge

click map to enlarge

While Virgin Orbit mentions a 500 km target orbit for 'Tubular Bells', earlier news reports on Brik-II mentioned a 600-700 km orbital altitude.

Brik-II is named for an earlier 'Brik', the name of the very first aircraft of the RNLAF progenitor, the 'Luchtvaartafdeeling', 108 years ago, in 1913:

The first Brik, photographed in 1916. Photo: Netherlands Institute for Military History

 

"Brik" has several meanings in Dutch. Originally it was a name for a type of ship (equivalent to the English 'Brig'), and it was also used for carts. Later, it became a name for old bicycles and old, decrepit  cars. "Brik" in addition is one of several Dutch names for a brick, hence the mission patch for Brik-II:

Brik-II mission patch (collection author)

Update 1 July 2021:

CSpOC TLE's have appeared on Space-Track for 8 objects from the launch: the seven payloads and the LauncherOne upper stage. They have catalogue numbers 48871 to 48878. The first object, 48871, is in a lower orbit  of 418 x 504 km and almost certainly the LauncherOne upper stage. The seven others are close together in higher, approximately 495 x 522 km orbits, inclined between 60.66 to 60.70 degrees.

Of these objects, either object D, E, or F (catalogue nrs. 48874, 48875, 48876) appears to be Brik-II.

My pre-launch estimate for the orbit appears to have a quite reasonable agreement with the eventual orbits for these objects (the green arrow and object in the images below indicates my pre-launch estimate. the plot is for 1 July 6:35 UT,  about 16 hours after launch):

click images to enlarge

Launching cubesats from the X-37B OTV 5: lifetime modelling with GMAT

image: USAF

Last week, CSpOC issued catalogue entries for three cubesats released as part of the X-37B mission OTV 5.

It concerns USA 295 (2017-052C), USA 296 (2017-052D) and USA 297 (2017-052E). No orbital data are given, but the catalogue entry did explicitly indicate that all three are no longer on orbit.

That cubesats were released as part of this X-37B mission had been clear from a US Air Force statement made after completion of the OTV 5 mission in October last year. The wording of that statement is however ambiguous: while most analysts take it to mean the cubesats were released by OTV 5, it is also possible that they were released as ride shares by the upper stage of the Falcon 9 rocket that launched OTV 5 in 2017.

In this blog post, I will do an academic exercise aimed at guessing when, at the latest, these cubesats could have been released by OTV 5, assuming release from the latter.

OTV 5, the 5th X-37B mission, was launched from Cape Canaveral on 7 September 2017. It landed at the Kennedy Space Center Shuttle Landing Facility on 27 October 2019, after 780 days in space. Unlike previous missions that were all launched in 38-43 degree inclined orbits, this one was launched into a 54.5 degree inclined orbit. Combined with the fall launch date, this meant it took our tracking network a while to locate it on-orbit: the first positive observations were made in April 2018, half a year after launch.

From April 2018, when we started to track it, to October 2019, when it landed, OTV 5 orbitted at various orbital altitudes between 300 and 390 km altitude (see diagram below):

click diagram to enlarge

The CSpOC catalogue entry lists all three cubesats that were released as part of this mission as "no longer on orbit". Assuming they ended their orbital life by natural decay (rather than, for example, being retrieved by OTV 5 again at a later stage, which is in theory certainly possible!), the fact that they were no longer on orbit by 11 February 2020 might yield some constraints on when they could have been released.

To get some idea of the orbital lifetime of a cubesat released from OTV 5, and spurred on to do so by Jonathan McDowell, I ran several GMAT models in which I modelled a 5 kg 3U cubesat released at three altitudes: 400 km, 360 km and 325 km.

We do not know the actual orbital altitude of OTV 5 at that  moment. Nor do we know when the cubesats were released. Hence the three altitude variants. The start point of the modelling was an assumed release into the OTV 5 orbit on October 7, 2017, one month after launch of OTV 5.

For each cubesat, the models were run in two variants: one with the cubesat in minimal drag orientation (0.01 m² cross section), and one with the cubesat in maximal drag orientation (0.03 m² cross section). I used the MSISE90 atmosphere in the model, with historic Space Weather data for October 2017 to February 2020 and estimated solar and geomagnetic activity parameters from the 'early cycle' variant of the GMAT Schattenfile for dates past early 2020.

For the three assumed orbital altitudes and an assumed release one month after OTV 5 launch, the GMAT data produce the orbital decay plots below. In these plots, the red data are for minimal drag orientation, the blue data for maximal drag orientation. If the cubesats in question were similar to NRO's Colony II cubesats, then the red minimum drag orientation curves probably represent the orbital evolution best. If they were more like Colony I cubesats, then the blue maximal drag curves are more representative.

Taking the minimal drag variants, and under the assumption that the cubesats were 3U cubesats and not retrieved on-orbit by OTV 5 at a later stage, the suggestion is a release below 350 km. Released at higher altitudes, they would still be on-orbit.

Assuming reentry before 11 February 2020 after natural orbital decay, a minimal drag orientation and release no lower and no higher than 325 km, the latest possible moment of release would be late August 2018, give or take a month to account for the uncertainties.

It appears we can rule this out however, because we know that OTV 5 was orbiting at 380 km altitude, not 325 km altitude, at that time. So the best guess (although one under many assumptions) is a release some time before August 2018, i.e. within 1 year after the launch of OTV 5.

It is still possible that the cubesats were released at a later date, but next retrieved while still on-orbit by OTV 5. If the cubesats were smaller than a 3U cubesat, a later release than August 2018 is possible as well.

Finally, given the ambiguity in US Air Force Statements on the matter, it is also possible that the cubesats were released from the Falcon 9 upper stage on the day of launch.

For more about the X-37B, and especially the active myth-making that seems to be at play around this secretive space-plane, see my earlier post here.

OTV 5 rising in April 2018. Click image to enlarge