A Trident-II D5 SLBM launch in the Atlantic on 21 September 2025: analysis of footage from Puerto Rico (UPDATED)

frame stack of movie by SAC station Anasco, Puerto Rico

 

click map to enlarge

On 15 September 2025, Navigational Warnings appeared that pointed to an upcoming Trident-II D5 SLBM (Submarine Launched Ballistic Missile) unarmed test launch in the Atlantic between 17 and 22 September 2025, from a submarine of either the US Navy or UK Royal Navy positioned some 400 km out of the coast of Florida (update 24 Sept 2025: according to this US DoD bulletin it was an American test launch from an unnamed Ohio-class SSBN (Ballistic Missile submarine). The submarine test-launched four Trident missiles between Sept 17 and 21). I have posted about such tests and the typical pattern of Navigational Warnings associated to them earlier, in an analysis of a Trident launch that was inadvertently captured on camera in a time-lapse by an amateur astronomer on La Palma in September of 2013.

And now we have another case of inadvertant capture on camera of such a launch, and a second opportunity for analysis! 

In the evening of 21 September 2025 near 23:30 UTC, eyewitnesses in Puerto Rico saw a fuzzy object and what looked like expanding missile exhaust clouds move through the sky, consistent with a rocket or missile launch. The event was captured by amongst others a meteor camera of the Caribbean Astronomy Society (SAC) near Anasco, Puerto Rico. 

Eddie Irizarry of SAC was so kind to send me the video footage for identification and analysis. Immediately, it was clear to me that the video showed the Trident test launch we expected.

In top of this post is a frame-stack from the footage. Below it is a map I prepared showing the northern part of the sky as seen from the camera station in Puerto Rico, with the blue line representing the sky trajectory expected for this Trident launch for an assumed (but see below) apogee altitude of 2200 km. They compare well (note: the video stack shows a part of the trajectory only, up to about azimuth 30 degrees, while the sky map shows the full trajectory).

Here is the video footage itself (courtesy of  Eddie Irizarry, used with permission):

 

 

The trajectory for this Trident test launch is known, as it can be reconstructed from the Navigational Warnings that have been issued for it. Below is the Navigational Warning, and a map where I have plotted the exclusion zones A-D from it, and a fitted ballistic trajectory:

151958Z SEP 25
HYDROLANT 1538/25(GEN).
ATLANTIC OCEAN.
DNC 01, DNC 16.
1. HAZARDOUS OPERATIONS 171830Z TO 220136Z SEP
   IN AREAS BOUND BY:
   A. 28-34.00N 076-29.00W, 29-07.00N 076-28.00W,
      29-05.00N 075-33.00W, 28-30.00N 075-35.00W.
   B. 28-37.00N 075-51.00W, 28-55.00N 075-44.00W,
      27-44.00N 070-28.00W, 27-05.00N 070-28.00W.
   C. 16-28.00N 044-01.00W, 17-01.00N 043-43.00W,
      14-36.00N 038-46.00W, 13-37.00N 039-33.00W.
   D. 10-35.00S 001-40.00W, 10-05.00S 001-25.00W,
      12-01.00S 002-21.00E, 12-45.00S 002-55.00E,
      13-11.00S 002-20.00E, 13-01.00S 002-02.00E,
      13-04.00S 002-00.00E, 12-38.00S 001-15.00E.
   E. 26-58.00N 070-28.00W, 28-14.00N 070-28.00W,
      25-56.00N 063-20.00W, 24-34.00N 063-50.00W.
2. CANCEL THIS MSG 220236Z SEP 25.

click map to enlarge

 

On the map, I have undicated the part of the trajectory that was captured by the SAC camera on Puerto Rico as a yellow line. 

Area A is the launch area where the submarine is located. Areas B, E and C are respectively the splashdown zones of the first, second and third stages of the missile. Area D is the RV (Reentry Vehicle) target zone. The switched designations for the C and E area are probably a clerical error.

The launch area, 400 km out of the Florida coast is one of two well established launch locations for Trident tests in the Atlantic (see my earlier investigation here). Likewise, the target area in the southeastern part of the Atlantic, 900 km east of St Helena at a range of about 9500 km from the launch site, is a well known target location for these test launches.

What cannot be well gleaned from Navigational Warnings alone, is the apogee altitude of this test. 

In this post, I will however reconstruct it from a combination of the known missile flight trajectory and measurements of the missile's sky track in the video footage from Puerto Rico, in a similar way as I analysed the earlier 2013 Trident observation from La Palma. For that 2013 test, I found an apogee at ~1800 km.

The video (the original is higher resolution than the version posted in this blogpost) provides plenty of reference stars to do astrometry on the missile path through the sky. So I measured the missile's position with respect to the stars for several frames from the video. Plotting  these observed positions (in RA/DEC) on a star map along with the expected sky trajectories in RA/DEC for various assumed apogee altitudes (based on the trajectory from the Navigational Warnings), it is clear that an apogee of 2200 km fits best. Red crosses in the plot below are the measured positions from the video: the blue lines provide the expected missile tracks for various apogee altitudes:

click map to enlarge

(note that I choose to plot RA on the Y-axis rather than X-axis, in order to get a plot orientation that is most easily compared to the video footage).

Earlier, while similarly analyzing the Trident launch seen from La Palma in 2013, I found an indicated apogee of ~1800 km, some 400 km lower than seems to be the case with this latest test launch. Both values are significantly higher than the ~1200 km that is often taken as a canonical value for an intercontinental missile apogee. These tests in the Atlantic therefore appear to be a bit "lofted", perhaps simply to keep the Reentry Vehicle (RV) impact area sufficiently out of the African coast.

From the timing of the Puerto Rico video, the actual launch time was likely somewhere near 23:27 UTC (Sept 21) from a location  near 28.8 N, 76.3 W, with a flight time near 41 minutes from launch to RV impact. As seen from Puerto Rico the missile cleared the horizon while at ~150 km altitude, steadily climbing to  ~800 km when it left the field of view of the CAS camera station (while continuing its ascend towards apogee). The closest slant range to the camera station was ~1300 km. The big cloud of exhaust gas seen in the early part of the video likely stops upon ejection of the second or third stage. The various smaller "pufs" of exhaust cloud that can be seen later emanating from the fuzzy object, are probably due to either the third stage or post-boost vehicle orienting itself.

(With thanks to Eddie Irizarry/CAS for sending me the footage and for his permission to use it in this blog) 

UPDATE 24 Sept 2025: 

According to this US DoD bulletin the missile was launched from an unnamed US Ohio-class Ballistic Missile submarine (SSBN). The submarine reportedly test-launched as much as four Trident missiles of the 5DLE variety between Sept 17 and 21. The below image was published, showing a Sept 21 nighttime launch, the missile that was seen from Puerto Rico:

 

Sept 21 2025 Trident missile launch. Photo US Navy/Shelby Thompson

An upcoming British Royal Navy Trident SLBM test in the Atlantic [UPDATED]

click map to enlarge

Over the past month, there was much anticipation for a (almost certainly) British Royal Navy Trident-II D5 SLBM test in the Atlantic. The arrival of the British nuclear ballistic missile armed submarine HMS Vanguard and several support ships at Port Canaveral in the past weeks suggested as much. Port Canaveral is the home base for such Trident SLBM tests.

And now the corresponding Navigational Warnings have appeared, for the period January 30 - Feb 4.

290215Z JAN 24
NAVAREA IV 89/24(GEN).
NORTH ATLANTIC.
WESTERN NORTH ATLANTIC.
1. HAZARDOUS OPERATIONS 302100 TO 040356 FEB
   IN AREAS BOUND BY:
   A. 29-00.00N 079-56.00W, 29-05.00N 079-35.00W,
      29-00.00N 079-07.00W, 28-38.00N 079-06.00W,
      28-36.00N 079-33.00W, 28-42.00N 079-52.00W.
   B. 28-28.00N 076-03.00W, 28-19.00N 075-04.00W,
      28-06.00N 075-07.00W, 28-16.00N 076-01.00W.
   C. 27-03.00N 069-40.00W, 27-20.00N 069-37.00W,
      26-58.00N 068-02.00W, 26-43.00N 068-05.00W.
   D. 19-42.00N 050-06.00W, 20-19.00N 049-55.00W,
      19-02.00N 046-24.00W, 18-23.00N 046-46.00W.
   E. 08-32.00N 031-06.00W, 08-39.00N 031-01.00W,
      08-03.00N 028-55.00W, 06-43.00N 027-40.00W,
      05-49.00N 028-16.00W, 05-59.00N 028-34.00W,
      05-25.00N 028-53.00W, 06-25.00N 029-17.00W.
2. CANCEL NAVAREA IV 88/24
3. CANCEL THIS MSG 040456Z FEB 24.

I have depicted the five hazard zones from this Navigational Warning (also issued as HYDROLANT 214/24, and a re-issue of an earlier warning that had a typo in the coordinates of Area A) in the map in top of this post. Area A is the launch area. Areas B, C and D are the splash-down zones of the first, second and third stages. Area E is the RV target area.

The launch is from one of two standard test firing areas, some 80-90 km in front of the coast of Florida (see also this earlier post). The launch will be visible from Florida, so from previous experience I expect it to generate a number of 'UFO' reports from eyewitnesses who don't know what they are seeing.

The first thing of note is that the range of this test, at approximately 5900 km, is rather short compared to other Trident tests.

That can be seen in the map below, which depicts the RV target area of this test along with the target areas of earlier Trident-II D5 tests fired from the same test launch area 1.

click map to enlarge

Whereas the other RV target areas are at latitudes 9 S to 18 S, the target area for this test is much more north, near latitude 7 N, i.e. a range some 3000-5000 km short of earlier tests. It is effectively about half the range of a typical Trident test.

HMS Vanguard (S28) has recently come out of a long 7.5 years maintenance overhaul and refuel period, and this test likely is part of its recertification as an operational SLBM submarine. The Royal British Navy has four Vanguard-class submarines in active service. Each of them carries 16 Trident-II D5 missiles.

In June 2016, the previous Royal British Navy Trident missile test, a Trident test-fired from HMS Vengeance, went awry when the missile veered into the wrong direction (towards Florida) after launch: according to newspaper The Guardian because if was given wrong trajectory information. It had to be destroyed in flight. That test targetted a target area just east-southeast of Ascension Island. I guess some nervous officials will watch the upcoming launch carefully with their finger on the destruct button.

UPDATE 21 Feb 2024:

The missile test failed, according to UK Media (.e.g. BBC here and The Sun here). It appears that the first stage did not ignite after missile ejection from the submarine. As a result, the missile plunged back into sea close to the submarine. The test was reportedly witnessed by the UK Defense Secretary Shapps and the Commander of the Royal Navy, so I guess there was a lot of Stiff Upper Lip that day, with some "Ow well, that's unfortunate Old Boy...".
A previous UK Royal Navy test launch, in 2016, failed as well (see discussion above in blogpost).

Analysis: The re-entry of the CZ-4B r/b 2014-049C observed by a Dutch pilot on May 27 [UPDATED]

click to enlarge. Image (c) Christiaan van Heijst, used with permission

click to enlarge. Image (c) Christiaan van Heijst, used with permission

The beautiful, spectacular images of a rocket stage re-entry above were made by the Dutch aviation photographer and pilot Christiaan van Heijst,  the co-pilot of a Cargolux freight aircraft (flight CV760, a Boeing 747-8 with registration LX-VCC) en route to Brazil on May 27, 2017.

While cruising at FL 340, 34 000 feet (10.360 km) over the mid-Atlantic, Christiaan noted a group of 7 to 10 bright yellow, very slow fireballs appearing in the corner of his eye. Here is the story as told by Christiaan on his facebook page:

Suddenly I noticed something in the corner of my eye. I looked to my right and to my own surprise I saw a huge group 7-10 of bright yellow lights move parallel to our track with a much faster speed and very high altitude. This was not an airplane, nor was it a meteorite. Where shooting stars / meteorites often leave a bright trail, they move with very high speed and burn up quickly. This cluster of lights moved far too slow to be a meteorite and its light was far too constant to be an ordinary meteorite. 

Immediately, a lot of excited chatter in Portuguese and other (African) languages I could not identify. was opening up on the frequency we had tuned in. Apparently lots of pilots were seeing the same lights, which is not surprising with such a high and bright appearance. All in all, the lights appeared abeam our aircraft and disappeared on the horizon in roughly two minutes time, keeping their intensity and appearance along the way.

Evidently, what Christiaan and his colleagues were witnessing was a spectacular re-entry of space debris, with the re-entering object breaking up in multiple pieces while it was plunging through the atmosphere. The time of this re-entry event was around 23:18 UT on May 27, 2017, while the aircraft was over the mid-Atlantic near 11^o.93 N, 33^o.28 E (see also later in this post).

In this blog post, I identify the object responsible and provide some model results for this re-entry.

click map to enlarge

Christiaan van Heijst initially thought that this re-entry event was related to a NOTAM issued mid-May, a warning for the splash-down of a Soyuz 2nd stage during the SES-15 launch from Kourou. This launch however had already happened 10 days earlier, on May 18, so evidently was no explanation for this event. Christiaan next posted his story on Facebook, hoping that someone could identify the object responsible.

I was allerted to Christiaan's Facebook post by one of my Twitter followers, Theo Dekkers and could quickly identify the event as the re-entry of 2014-049C, a Chinese Chang Zheng (Long March) 4B (CZ-4B) upper stage from the launch of the Chinese Gaofeng 2 and Polish Heweliusz satellites in August 2014. Time, location, and movement of the witnessed event agree extremely well.

Two days before the sighting, JSpOC had started issuing TIP (Tracking and Impact Prediction) messages for this object via their Space-Track portal. The final TIP message, issued after the actual re-entry, lists the re-entry time as 27 May 23:17 +- 1 min UT, near 15^o.7 N, 34^o W (by the way: we actually believe that such times accurate to 1 minute originate from infrared observations of the re-entry fireball by US SBIRS early warning satellites).

click to enlarge

This time and position closely agrees with the observations of the aircraft crew and the aircraft position. Christiaan van Heijst provided me with a photo of the aircraft flight instruments taken about one minute after the event. It shows the time of that moment, 23:20:43 UT, and the aircraft's GPS coordinates and altitude: 11^o 56.1' N (11.935 N), 33^o 17.3 W (33.288 W) at a flight level of 34 000 ft (10.360 km). [edit: the altimeter in the image above says 33 960 feet but Christiaan informed me that it has a small error and they were flying at FL 340]. The aircraft was heading towards a magnetic bearing of 219 deg, which corresponds to a true bearing of 204 degrees (towards the S-SW).

The time and position are very close to that of the TIP: a difference of about 425 km between the TIP re-entry location and the location of the aircraft, and 1-2 minutes in time.

The sky track of the re-entering space debris that can be seen on the photographs also agrees well with the predicted sky track of 2014-049C for the aircraft's location. Below is the predicted track for 2014-049C for the location of the aircraft based on a propagated version of the last available orbital element set for the object. The blue line is the predicted track in the sky, the yellow arrow the approximate trajectory for the brightest fragment visible on Christiaan's photographs:

click to enlarge

There is a discrepancy, in that the observed trajectory is some 11 degrees lower in the sky than the predicted trajectory, with a time lag as well. However, this is what you expect. The track shown is for the pre- re-entry orbital altitude (about 134 km). During the re-entry phase, the altitude of the object however quickly drops, and as a result the observed track will be located significantly lower in the sky. As the object is slowed down by increasing drag of the atmosphere, it starts to lag behind predictions in time as well. At the time of the re-entry, the object was already below 80 km altitude,  40% or more below its orbital altitude.


[UPDATE  6 Oct 2017:]

I have since used the output of a GMAT re-entry model (see below) to reconstruct the expected trajectory in the sky as seen from the aircraft. For this purpose, I used the latitude, longitude and altitude output of the GMAT model, converted these to ECEF coordinates, did the same for the position of the aircraft, and then with the help of relevant equations calculated the azimuth and elevation of the reentering rocket stage as seen from the aircraft from these. The sky positions were plotted on a star map for the location of the aircraft. The result is below (compare to the two photographs in top of this post):

click map to enlarge

As can be seen, the modelled sky trajectory, while not a perfect fit, is nevertheless very close to that visible on the photographs.

Note that the GMAT reentry model, while modelling the influence of the atmosphere, does not take fragmentation and ablation (and from that mass-loss and changes in surface:mass ratio) into account.

[END OF 6 Oct 2017 UPDATE]

To gain insight into the positions and altitude of  the re-entering debris over time relative to the aircraft, I have modelled the re-entry event. I propagated the last five known orbital element sets (TLE) for 2014-049C to its last ascending node passage before re-entry, using SatAna and SatEvo. The resulting, final, pre- re-entry TLE was next used as the starting point for a ballistic simulation in GMAT, using the MSISE90 model atmosphere and actual Space Weather data. With this input, I had GMAT calculate positions and altitudes of the re-entering object over time.

Such modelling always is an approximation only. There are a number of unknowns, one of which is the spatial orientation of the major axis of the re-entering rocket stage with regard to its flight direction. This adds uncertainty to modelling the atmospheric drag experienced by the re-entering rocket stage, which introduces uncertainties in the position and altitude of the stage for a certain time. A CZ-4B 3rd stage is a tube measuring 6.24 x 2.90 meter with a dry mass of about 1 metric ton. The drag experienced depends on whether its longest dimension is facing the flight direction, its narrow end, or whether it tumbles. For the modelling, I choose to use a drag surface that is 50% of the maximum drag surface possible. Breakup of the rocket body, which is evidently happening (see the copious fragmentation in the photographs) adds more uncertainty, as fragmentation drastically alters the drag surface and surface-to-mass ratio. As the images show, the trajectories of individual fragments clearly start to diverge as a result of this. The model, however, treats the re-entering body as one single body with no mass loss.

So, Caveat Lector. But let us look at the results. Mapping the GMAT results along with the position and bearing of the aircraft a minute after the event, yields this positional map and this altitude versus time profile:

click map to enlarge

click diagram to enlarge

For the reasons mentioned above, the altitudes versus time in the diagram are approximations only, with a possible uncertainty of perhaps 25% for a given time instance.

Compared to the JSpOC TIP data, the resulting trajectory I modelled seems to be slightly on the 'early' side, in that it passes the JSpOC location about a minute too early. On the other hand, the time in the TIP is given with an accuracy of no better than 1 minute, and an unspecified inaccuracy in the coordinates of the geographic location as well. What we can conclude from the modelled positions relative to the aircraft, is that the sighting definitely matches the 2014-049C re-entry data closely.

If my modelling is somewhat correct, the re-entering debris was moving from altitudes of ~95 km at the start of the sighting to below 50 km near the end [update 6 Oct 2017: The closest it came to the aircraft was a line-of-sight minimum distance of 157 km near 23:16:50 UT]. It is uncertain whether anything survived to sea level c.q. aircraft flight level. Usually, most materials have burned up before they could reach the surface: it is however not impossible that some pieces nevertheless survived and splashed down in the Atlantic. Notably the pressure spheres of rocket engines tend to survive. If anything, the modelling shows that any surviving debris was well ahead of the aircraft once it reached the flight level of the aircraft.

Ted Molczan has done a similar modelling with similar results. The differences that do exist between Ted's analysis and my results, are due to the choice of slightly different starting parameters for the model.

The final spectacular demise of 2014-049C was the result of a long drop that started short after launch. Below I have mapped the evolution of the orbital altitude of the rocket booster over the past years, starting just after launch:

click diagram to enlarge

The quick decay of (notably) the apogee altitude, but also perigee, can be clearly seen. Early 2017, the drop in altitude starts to increase exponentially. At 23:17 UT on 27 May 2017, after 15772 revolutions around the planet since launch, it was the final end for 2014-049C.

Christiaan asked me why there was no NOTAM issued for this re-entry. NOTAMS or Area Warnings are however generally only issued for controlled de-orbits, and first and second stage splashdowns during launches. Reasonably accurate locations can be predicted in advance for these. For uncontrolled re-entries, such as this event, this is not the case. There are so many uncertainties that anything approaching an accurate prediction can only be issued during the last hour or so before re-entry.

(note 1: for some Frequently Asked Questions about re-entries, see an earlier post here).
(note 2: this post was updated on 6 October 2017 to add some new modelling results)

Acknowledgement: I thank Christiaan van Heijst (www.jpcvanheijst.com) for providing extra information and for his permission to use his photographs. I thank Theo Dekkers for pointing me to Heijst's observations.

[UPDATED 2x] Visualizing the trajectory of the September 10 Trident missile test in the Atlantic

The past days I have covered the story about German astrophotographer Jan Hattenbach's September 10 strange photographic observations from La Palma on this blog. Along with Jonathan McDowell I quickly suspected this was a  missile test launched from a submarine in the Atlantic. This was later confirmed: Lockheed-Martin and the US Navy announced that it was a test with a Trident II D5 SLBM launched from a submerged Ohio-class submarine.

More information next emerged that contained some clues to the launch trajectory. Now Cees Bassa has done an extensive analysis, modelling a trajectory. The details can be found here on the Seesat-L mailing list. He finds a launch location near 28 N, 68 W, more to the west than I initially thought.

I used Cees' results on the launch location and STK to fit a ballistic trajectory through Cees' launch location and the probable target area discussed earlier. The trajectory (visualized below) fits well with the altitudes and azimuths as photographically observed by Jan Hattenbach from La Palma (see astrometry in the appendix to my post here).

click maps to enlarge

The trajectory STK fits allows to say something about altitudes and flight-times. The launch occurred near 21:10:40 UT. After a 36 minute flight over a distance of 8660 km, the target area between St. Helena and the Gabon/Congo coast was reached near 21:47:00 UT. In the top of its ballistic trajectory, the missile reached an altitude of 1800 1900 km.

(note added 27 Sep 2013, 13:00 UT : Cees Bassa has since released the detailed data of his ballistic curve fitting: he has the apogee somewhat lower, at 1650 km, and a flight time between 21:10:00 UT and 21:44:45 UT, one minute faster. Please note that the diagrams below are based on the STK derived trajectory I cobbled together, not Cees' data.

Update 28 sep 13:00 UT: Cees' trajectory does not have the impact point in the published exclusion zone, but somewhat to the East of it. That is the major cause of the discrepancy between the results Cees published, and the ballistic trajectory I present here, which does land squarely in the exclusion zone. With the impact point shifted slightly westwards, the apogee altitude shifts upward if one wants to match the azimuth/elevation data from La Palma.)

click diagrams to enlarge

The two events at 21:17:08 and 21:08:43 UT that I initially misidentified as the 2nd and 3rd stage ignitions, but which are, as Jonathan McDowell pointed out, likely the MIRV bus and MIRV separations, happened at 1130 and 1330 km altitude in the ascending phase, after 6.5 and 8 minutes of flight-time, 1860 respectively 2235 km from the launch location. They are marked in the diagram below:

click diagram to enlarge

(note: for this post I am much indebted to Cees Bassa and his fine analysis. His trajectory reconstruction provided the basis for the diagrams and the timing and altitude information in this post. Cees' own detailed trajectory data can be found here - they slightly differ from what I present above, but see the note elsewhere in the post above.)

More on the September 10 mid-Atlantic Trident SLBM test captured by astrophotographer Jan Hattenbach

On September 20 I blogged with an analysis of photo's taken from La Palma on September 10 near 21:18 UT by German astrophotographer Jan Hattenbach. The pictures showed a strange phenomena which was quickly suspected to be a SLBM test. A suspicion that was confirmed yesterday when Lockheed and the US Navy announced they indeed tested a Trident II D5 missile that day, launched from a submerged Ohio-class submarine in the Atlantic.

Since then, more discussions have ensued on the SeeSat-L mailing list. Chiming in were amongst others Ted Molczan, Jonathan McDowell, Allen Thomson and Cees Bassa. These discussions and new pieces of evidence provide a possible target area for the test, and if some of the things brought up are correct, indicate that the launch location, the trajectory and imaged part of the flight path might be somewhat different from my initial assessment (which as I noted was very rough and very approximate: there was a reason I didn't provide a detailed map)

First, Ted Molczan managed to dig up a Broadcast Warning to mariners for the south Atlantic (that I was not able to trace to a URL). The text:

( 090508Z SEP 2013 )
HYDROLANT 2203/2013 (57)  
(Cancelled by HYDROLANT 2203/2013)

SOUTH ATLANTIC.
ROCKETS.
1. HAZARDOUS OPERATIONS 091400Z TO 140130Z SEP
   IN AREA BOUND BY
   09-18S 000-26W, 09-50S 000-32E,
   12-03S 002-39E, 13-40S 004-09E,
   14-09S 003-49E, 13-06S 001-56E,
   11-05S 000-58W, 10-55S 001-05W,
   09-56S 000-50W.
2. CANCEL THIS MSG 140230Z SEP 13

Ted speculates that the area indicated is the target area of the (dummy) warheads from the Trident. Indeed, it is about 7000 km away, well within the ~11 000 km range of the Trident missile, from the general launch area I deduced earlier (but see below). It would mean my launch azimuth estimate was off by 40-45 degrees (and closer to 130 degrees). And it could very well be given that it was a very rough deduction from observations from only one location, with several assumptions involved. To reconstruct it properly, you need observations from two locations, so you can triangulate.

The potential target area is in the eastern part of the South Atlantic, between St. Helena and the coast of Gabon and Congo. It is elongated and the major axis of the polygon might be indicative of the launch direction. In that case, the missile trajectory was approximately as pictured below (Red line: missile trajectory. Yellow lines: sightlines from La Palma for the range I astrometrically measured (21:17:08 to 21:19:42 UT): this does not include the earliest part where it emerged from the horizon as seen from La Palma. The grey polygon is the potential target area mentioned in above Broadcast Warning).

click map to enlarge

Meanwhile, the actual launch location is a point of discussion as well. In my earlier analysis, I interpreted two distinct events in the  photographed trail as the moments the 2nd and 3rd stage of the missile kick in:

 Jonathan McDowell has a different suggestion: he thinks these moments represent the MIRV bus and MIRV (the warheads) separations. These happen at much higher altitudes than the rocket stage burns. It would mean the object(s) were at a much larger range from La Palma than I deduced from my earlier notion it were the 2nd and 3rd rocket stage burns. It would shift the launch location significantly more to the Northwest (see map above).

BREAKING: the September 10 La Palma event WAS a Trident missile test!

In an earlier post I analyzed a mysterious sighting by German astrophotographer Jan Hattenbach from La Palma on the Canary Islands on September 10.

Based on an analysis of his photographs, I concluded that what he serendipitously captured was most likely an unannounced SLBM (Submarine Launched Ballistic Missile) test in the mid-Atlantic, possibly a US or British Trident test.

News has just broken that the US Navy in cooperation with Lockheed-Martin indeed conducted a test with a modified Trident II D5 Submarine Launched Ballistic Missile in the mid-Atlantic on September 10 (and again on September 12). The Trident D5 missile was launched from a submerged Ohio-class submarine.

(Tip of the Hat to Brian Webb who first brought up the confirmation news today at the SeeSat-L list)

[UPDATED: confirmed!] A clandestine launch in the Mid-Atlantic on Sep 10, captured by a German astrophotographer?

UPDATE 24 Sep 2013 18:00:
It has now been confirmed that this was a US Trident SLBM test launched from an Ohio-class submerged submarine! So I was right!
(note added 25 Sep 2013: a post with more info subsequently come to light and an update on the probable launch trajectory is available here)

click image to enlarge

In the evening of September 10, 2013, German astrophotographer Jan Hattenbach was taking images with an f2.8/24mm lens near the GranTeCa dome, at 2300 meter altitude at the Roque de los Muchachos observatory on La Palma in the Canary Islands. His camera was looking due west, out over the Atlantic Ocean, in the direction of Bootes and Virgo. The intention was to create a time lapse movie.

Between 21:16 and 21:20 UT, he captured something unexpected on his images. A strange fuzzy bright object moved over the images, spouting cloudy puffs. Above is a stack of the images: it shows the GranTeCa dome, star trails, a normal satellite (Kosmos 1410)...and the strange cloudy phenomena coming under an oblique angle from the horizon. Below is a short movie made from the images (5 second images with a 2 second interval). Note that it is a time-lapse that speeds up the event: the whole phenomena took about 2.5 minutes in real time:



Jan wrote about his strange observation on his own blog (in German) and posted his story on the AKM forum and on Twitter. Rainer Kresken forwarded it to the SeeSat-L mailinglist, and science writer/journalist Daniel Fischer tweeted to Jonathan McDowell and me whether we could explain the phenomena. Next, Jan was so kind to make his original imagery available to me.

Initially Jan reported that the images were taken near 21:23 UT (Sept 10, 2013). However, it turned out that his camera clock was off by several minutes. The event in reality happened earlier.

Luckily, a "normal" satellite is visible in the image sequence too, briefly flaring, and Cees Bassa and me could identify that satellite as Kosmos 1410 (82-096A). As the orbit of this object is known, astrometry I performed on the trail yielded the correct image times. Jan's camera clock was off by 6m 17s, as it turned out. The phenomena took place between 21:16 and 21:20 UT.

After seeing the images, my first thought was that this could be a fuel vent by a rocket booster in Earth orbit. The time and trajectory did however not match any known object, unclassified or classified.

Another option was a satellite launch. There were however no launches scheduled for this date (and this includes launches of classified objects, which you really cannot keep secret. They are publicly announced as it involves temporary restrictions to airspace down te launch trajectory, and a very visible rocket ascent from Vandenberg or Canaveral).

At that point, I started to suspect that it could perhaps be a hush-hush suborbital ballistic missile launch test, similar to the September 2, 2013, US-Israeli missile test in the Mediterranean. Harvard space historian Jonathan McDowell communicated a similar suspicion, noting that the particular part of the Atlantic has seen Poseidon SLBM tests in the past.

The thing is, that no such test was announced for this date. For example, I have found no NOTAM's  restricting airspace over parts of the Atlantic because of a missile launch. That does not mean it is not a missile test though. It just means that whoever did the test, doesn't want to acknowledge it and preferred no-one to know about it. The September 2, US-Israeli test in the Mediterranean was not announced either (it came to light because it was detected by a Russian Early Warning Radar).

If the event seen from La Palma was indeed a clandestine Medium Range Ballistic Missile test (such as I believe is the case), the primary suspects are the Unites States or Great Britain, who both operate the Trident Submarine Launched Ballistic Missile (SLBM); or the French, who operate the M45 and M51 SLBM.

Several points in the observation fit a SLBM test. The US/British Trident and the French M45/M51 are 3-stage missiles. In the stacked image and movie above, there are two sudden bursts of brightness in the trail, both accompanied by an expanding puffy cloud. I interpret these as the moments of jettison of the 1st stage and ignition of the 2nd stage (note: but see update here); and ejection of the 2nd stage and ignition of the 3rd stage. I have marked these moments, taking place at 21:17:08 and 21:18:43 UT (so with a 1m 35s separation), in below detail of the stacked image. The corresponding astrometric positions of these points are RA 205.061, Dec -3.950, and RA 211.366, Dec -6.153 degrees.

click to enlarge

Below are details from the single still images from those moments:

click image to enlarge

Below is a detail from a single frame just after what I interpret as the 3rd stage ignition, showing a bright fuzzy trail and expanding vapour clouds on both sides:

click image to enlarge

The duration of the event fits what is known of the Trident missile: from launch to 3rd stage ignition takes less than 2 minutes with the Trident. The 2nd stage ignites at about 70 km altitude, the 3rd at about 150km altitude.

A careful look at the stacked image shows that after what I interpret as the 3rd stage ignition, the trajectory clearly starts to deviate from the previous more or less straight line:

click image to enlarge

This is not an effect of lens distortion, as I will show below. It is a real deviation, that fits a missile launch. It shows unequivocally that the phenomena is not a fuel vent by a rocket booster in earth orbit. Such an object (moving in a Great Circle) would move in a straight line when positions are plotted in a Gnomonic projection. I did this for Jan's object: I astrometrically measured points on the trail and converted and plotted the measured RA/DEC in a gnomonic projection system. The same deviation that should not be there if this was an object in Earth orbit is visible in the RA/DEC data:

 

click diagram to enlarge

This makes very clear that Jan's object was not in orbit around the earth, but on a launch/ballistic trajectory. So we can definitely exclude a rocket booster orbiting the earth from a previous launch and venting fuel.

Just to support my previous argument further: here is what the trajectory in RA/DEC looks like for an object in an eccentric GTO orbit observed near perigee over a similar time span as Jan's object. The comparison object is the USA 40 rocket (1989-061D):

Assuming the La Palma event indeed was an unacknowledged Trident SLBM test by the USA or the British, the known specs of the Trident provide a (very) rough indication of where the launch took place.

As mentioned earlier, the 2nd stage of a Trident SLBM ignites at about 70 km altitude, the 3rd at about 150km altitude. As mentioned too above, I interpret two points in the trail to represent these moments. By measuring their astrometric position and calculating the corresponding azimuth and elevation in the sky, we can get a rough indication of distance and direction at these moments. I did this as a (please note) very rough back-of-the-envelope calculation. It suggests the launch took place near latitude 23-25N and a longitude several degrees West of  40 W. This is right in the middle of the Atlantic, at least 2000-3000 km from any coast in any direction. Again, that points to a Submarine launched missile. The launch azimuth is roughly 80-85 degrees, towards the African coast at a distance of over 3000 km. (note added 25 Sept: but see update here that somewhat changes the picture)

The USA was testing missile intercepts near Kwajalein in the Pacific that same September 10. It is however highly unlikely that the launch that Jan seems to have captured is directly related, for the simple reason that a Trident launched in the Mid-Atlantic does not have the necessary reach to get to Kwajalein.

It is a busy time with missile tests: after the September 2 test in the Mediterranean, the September 10 tests near Kwajalein, and this potential unacknowledged test captured by Jan Hattenbach that same date, there was also a missile test in New Mexico on September 13. The Kwajalein tests were scheduled well before, but the unannounced September 2 test in the Mediterranean and perhaps also this unacknowledged September 10 test in the Atlantic might be part of ad hoc military practise exercises in connection to the continuing situation with Syria.

One question some might raise: why a Medium range Ballistic Missile launch? Why can't this not be an unacknowledged launch into Earth orbit? First: it would not be possible to keep such a launch from a US landbased site a secret. It would be seen over a wide area (like the New Mexico test) and necessitate temporary closure of parts of airspace. Moreover, altitudes and directions really point to a launch in the Mid-Atlantic. The only way to launch into Earth Orbit over the Mid Atlantic would be by an airborne launch using a Pegasus rocket.

All in all, and given the context of the situation in Syria and the September 2 test in the Mediterranean as well, it is much more likely that this is an unacknowledged SLBM test, launched from a US, British or French submarine in the Mid-Atlantic.


UPDATE 24 Sep 2013 18:00:
It has now been confirmed that this was a US Trident SLBM test launched from an Ohio-class submerged submarine! So I was right! 

Update 25 Sep 2013: New post with new info here, including re-assessment of the launch trajectory

(note: I thank Jan Hattenbach for making available his original imagery and for his permission to use it on this blog. And I thank Cees Bassa, Jonathan McDowell, Rainer Kresken and Daniel Fischer for discussions. Conclusions and any errors are solely mine).


APPENDIX  - added 24 Sept 2013, 19:50

Below are the astrometric data I used in my analysis. I did not measure every image, but enough to describe the track of the object. Measurements were done with AstroRecord astrometric software. Only the start of each trail segment was measured, except for IMG_1848 where the point where it brightens (3rd stage ignition) was measured as well. The observing site is at 28.7564 N, 17.8889 W and 2300 meter altitude. Times are accurate to ~1 second.



IMG       UT        RA        DEC
1835      21:17:08  205.061  -3.950
1838      21:17:29  206.335  -4.418 
1840      21:17:43  207.272  -4.737 
1843      21:18:04  208.731  -5.228 
1846      21:18:25  210.137  -5.743 
1848      21:18:39  211.071  -6.089 
1848_ign? 21:18:43  211.366  -6.153 
1850      21:18:53  212.081  -6.416 
1852      21:19:07  213.008  -6.790
1853      21:19:14  213.489  -6.977 
1855      21:19:28  214.450  -7.388 
1856      21:19:35  214.907  -7.585  
1857      21:19:42  215.493  -7.786