Monday, 20 January 2020

Testing a new lens for GEO and HEO (SamYang 2.0/135 mm)

The past week brought some clear skies. It also brougt me a new lens, a SamYang 2.0/135 mm ED UMC.

This lens had been on my wish-list for a while, as a potential replacement for the 1979-vintage Zeiss Jena Sonnar MC 2.8/180 mm I hitherto used for imaging faint Geosynchronous (GEO) and Highly Elliptical Orbit (HEO) objects, objects which are typically in the magnitude +10 to +14 range.

The 2.0/135 mm SamYang lens has gotten raving reviews on photography websites, several of these reviews noting that the optical quality of this lens is superior to that of a Canon 2.0/135L lens. And this while it retails at only half the price of an L-lens (it retails for about 460 to 500 Euro).

While I have the version with the Canon EF fitting, the SamYang lens is also available with fittings for various other camera brands.

Focussing is very smooth and easy with this lens. Unlike a Canon-L lens, the SamYang lens is fully manual (both focus and F-stop), but for astrophotography, manually focussing is mandatory anyway. The general build of the lens is solid. It is made of a combination of metal and plastic.

While not particularly lightweight, the lens is lighter in weight than my 1979-vintage Zeiss (which is all-metal and built like a tank, in true DDR fashion). The SamYang has a somewhat larger aperture (6.75 cm) than the Zeiss (6.42 cm), meaning it can image fainter objects. It also has a notably wider field of view (9 x 7 degrees, while the Zeiss has 7 x 5 degrees).

So for me, this seemed to be the ideal lens for GEO and HEO.

And after two test nights I can confirm: this SamYang lens indeed is spectacularly sharp. The first test images, made on January 15 and 16, have truely impressed me. Even at full F2.0 aperture, it is sharp from the center all the way to the edges and corners of the image.

Here is a comparison of the image center and the upper right corner of an image, at true pixel level. There is hardly any difference in sharpness:

click to enlarge

The images below, taken with the SamYang on a Canon EOS 80D, are crops of larger images, all but one at true pixel level.

The first image is a test image from January 15, a nice clear evening. It shows two objects in HEO: a Russian piece of space debris (a Breeze-M tank), and the classified American SIGINT satellite TRUMPET 1 (1994-026A). Note how sharp the trails are (this is a crop at true pixel level):

Click image to enlarge

The next night, January 16, I imaged several geostationary objects (which at my 51 degree north latitude are low in the sky, generally (well) below 30 degrees elevation). While the sky was reasonably clear, there were lingering aircraft contrails in the sky, locally producing some haze. Geostationary objects showed up well however, better than they generally did in the Zeiss images in the past.

The image below, which is a crop of a larger image, is not true pixel size, but slightly reduced in size to fit several objects in one image. It shows the Orion Nebula, several unclassified commercial GEO-sats, the Russian military comsat KOSMOS 2538 (BLAGOVEST 14L), and the classified Italian military communications satellite SICRAL 1B (2009-020A):

Click image to enlarge

The images below are all crops at true pixel level. The first one shows the US classified SIGINT satellite PAN/NEMESIS I (2009-047A), shadowing the commercial satellite telephony satellite YAHSAT 1B. It also shows a number of other unclassified commercial GEO-sats.

PAN/NEMESIS 1 is an NSA operated satellite that eavesdrops on commercial satellite telephony (see my 2016 article in The Space Review).

Note that this image - just like the next images- was taken at very low elevation, and from a light-polluted town center.

click image to enlarge

The image below shows another US classified SIGINT satellite, Mentor 4 (2009-001A), an ADVANCED ORION satellite. It shadows the commercial satellite telephony satellite THURAYA 2 (more backgrounds on this in my 2016 article in The Space Review). At magnitude +8, it is one of the brightest geosynchronous objects in the sky (note how it is much brighter than THURAYA 2):

click to enlarge

The last image below again is a classified US military SIGINT satellite, MERCURY 2 (1996-026A). While 24 years old it is, together with its even slightly older sibling MERCURY 1 (which I also imaged but is not in this image), probably still operational:

Click image to enlarge

After these two test nights, I am very enthusiastic about the SamYang lens. It is incredibly sharp, also in the corners, easy to focus, goes deep (in terms of faint objects), and overall performs excellent. I also like the wide field of view (compared to the 180 mm Zeiss which I previously used to target GEO). Together with the equally well performing SamYang 1.4/85 mm, it might be the ideal lens for imaging GEO and HEO.

Astrometric data on the targetted satellites from these test images are here and here. The astrometric solutions on the star backgrounds in the images had a standard deviation of about 2".

Added 20 Jan 2020:

This last image (reduced in resolution to fit) was taken this evening (20 January) and shows Trumpet 1 (1994-026A) passing the Pleiades:

Click image to enlarge

Sunday, 19 January 2020

Imaging Starlink 2

click to enlarge

A new set of 60 Starlink satellites, Starlink 2 (the third launch), was launched by SpaceX early on January 7th. Over the past 10 days, all passes were in earth shadow for my 51 degree North latitude, but as of this weekend, the satellites start to make low visible passes in evening twilight.

Yesterday evening was one of the first opportunities. The Starlink satellite "train", already dispersing as their orbits are raised, would make a pass low south with a maximum elevation at 28 degrees, where they would enter earth shadow.

Conditions were dynamic, with fields of clouds moving in the sky. Initially, the part of the sky where they should be brightest was obscured by a cloud, so I pointed the camera more west and lower in the sky.

The image below is a stack of 65 images, 5 seconds exposure each with 1 second intervals, taken between 17:52:50 - 17:59:15 UT (representing a 6m 25s period), with a Canon EOS 80D and EF 2.5/50 mm Macro lens set at F2.8, 1000 ISO. There is a band of Starlink objects, diagonally from lower right to upper left crossing behind the tree. These are objects in the 'head' of the Starlink 2 main "train":

click to enlarge

When the sky near the satellite culmination point also cleared of the field of clouds, I repositioned the camera to that point and captured the last part of the main "train" tail.

The first image below is a stack of 10 images, taken between 17:59:30 - 18:00:30 UT, representing a 1-minute period. The objects can be seen entering earth shadow at left.

The second image below is a single shot image (5-second exposure) from that series, showing four Starlink objects.

click image to enlarge

click image to enlarge

Near their culmination point, the Starlink satellites were clear naked-eye objects, with a brightness of approximately mag. +2.5 tot +3.0.

The images were taken from the center of Leiden town in the Netherlands, in a twilight sky that suffers quite some light pollution.

Saturday, 28 December 2019

Nine months after the Indian ASAT test: what is left?

click to enlarge

Yesterday it was 9 months ago that India conducted its first succesful Anti-Satellite (ASAT) test, destroying it's MICROSAT-R satellite on-orbit with a PDV Mark II missile fired from Abdul Kalam Island. I earlier wrote several blogposts about it, as well as an in-depth OSINT analysis in The Diplomat (in which I showed that the Indian narrative on how this test was conducted, can be questioned).

Over the past year, I have periodically written an update on the debris from this test remaining on orbit. In this post I again revisit the situation, nine months after the test.

At the time of the test, the Indian DRDO claimed that all debris would have reentered within 45 days after the test. As I pointed out shortly after the test in my blogpost here and in my article in The Diplomat, that was a very unrealistic estimate. This was underlined in the following months.

A total of 125 larger debris fragments have been catalogued as well-tracked. Over 70 percent of these larger tracked debris pieces from the test were still on-orbit 45 days after the test (the moment they all should have been gone according to the Indian DRDO!).

Now, nine months after the test, 18 of these debris fragments, or 14 percent, are still on orbit. Their orbits are shown in red in the image in top of this post (the white orbit is that of the ISS, shown as reference).

In the diagram below, the number of objects per week reentering  since the ASAT test is shown in blue. In grey, is a future prediction for the reentry of the remaining 14% of debris. The last pieces might linger untill mid-2023:

click to enlarge

click to enlarge
All but four of the remaining pieces currently have apogee altitudes well above the orbital altitude of the ISS, in the altitude range of many operational satellites. Nine of them have apogee altitudes above 1000 km, one of them up to 1760 km. Their perigees are all below ~280 km.

click to enlarge

Saturday, 21 December 2019

The stars did not align well for Starliner, it seems

click map to enlarge

Yesterday's Boeing CST-100 Starliner Orbital Flight Test was a true nailbiter. This blogpost briefly reitterates what happened, and what could have happened had they not been able to eventually raise the orbit.

Launched atop an Atlas V rocket, this uncrewed inaugural test flight of the new Boeing Starliner crew transport vehicle should have gone on its way to a docking at the ISS today, followed by undocking and landing at the White Sands Missile Range a week from now. The map above which I prepared pre-launch from information in the Starliner Press Kit and Starliner Notebook, shows what should have been the launch track and some keypoints on that track. As we now know, it went wrong at one of these keypoints.

Launch was at 11:36:43 UT. The Atlas V and Centaur upper stage performed fine, the Centaur inserting the Starliner in a 76 x 191 km suborbital trajectory some 12 minutes after launch. Three minutes later, the Starliner separated from the Centaur.

Next, 31 minutes after launch near 12:08 UT, it should have fired its own thrusters, in order to raise perigee and in this way circularize the orbit, becoming truely orbital.

And that went wrong.

Due to a misfunctioning Mission Elapsed Time clock, the Starliner's orbit insertion burn did not go as planned. Initially, an "attitude problem" was reported as well. The next half hour or so was nailbiting, as Boeing and NASA were not quite coming forward with information, apart from the ambiguous comment that the Starliner had "stabilized" its orbit (which is extremely ambiguous wording).

Those of us who know about orbits, realised that if no orbit insertion burn took place, the Starliner would continue on a suborbital trajectory, and reenter with or shortly after the Centaur upper stage (see also the end of this post, where I modelled this). The Centaur reentry was expected to occur south of Australia at about 12:30-12:35 UT (see the map in top of this post), and as the clock approached that time, it became really nailbiting: was the Starliner crew module still on orbit, or breaking up and burning up over the Indian Ocean?

Eventually, it became clear that, many minutes after the original burn time, Boeing did manage to do a burn that raised perigee from 76 to 180 km.

As an interesting sidenote: during the post-launch press conference, Boeing's Jim Chilton seemed to suggest (at 7:25 in below video) that following the timer anomaly, they tried to uplink new commands, but were faced with delays caused by the relay satellite(s) used (TDRS). It also transpired that on a crewed flight, the crew itself would have intervened in this stage:

Orbital data released by CSpOC provided the first unambiguous information to the world about the whereabouts of Starliner. A pre-burn orbit appeared first, showing a 76 x 191 suborbital orbit. As this was pre-burn, this still did not say much about Starliner's state. But shortly after that, a 186 x 221 km orbit was published, somewhat later followed by a new 180 x 221 km orbit. These showed that Starliner had reached a safe orbit around the earth.

The diagram below shows the altitudes of apogee and perigee of the orbit published so far (21 december 12 UT): currently it is in a 241 x 265 km orbit.

click diagram to enlarge

The amount of fuel spent in the emergency manoeuvres after the planned burn did not occur, was thus that it was no longer feasible to reach and dock to the ISS. Over the night, a new burn or series of burns therefore raised the orbit to 241 x 265 km, 58.4 degree inclined, lining it up for a landing at White Sands Missile Range on Sunday 22 December.

The current orbit (epoch 19355.3601887) results in a landing opportunity at White Sands between 12:45-12:55 UT on Sunday 22 December, approaching the range from over the eastern Pacific, as can be seen in the map I prepared below:

click map to enlarge
This is based on the current (epoch 19355.3601887) orbit. If new orbit adjustments happen, the projected time of landing might change slightly (e.g. a lowering of the orbit would make the Starliner speed ahead a bit, resulting in a slightly earlier landing time).

[UPDATE 21 Dec 22:15 UT: NASA has announced that the landing will be around 12:57 UT]

What if the orbit raise had failed completely?

Starting from the first, pre-boost orbit released, 76 x 191 km, I used GMAT to model what would have happened. I find that the Starliner, had it continued in that orbit, would have reentered over Polynesia around 12:50 UT,  about 1h 15m after launch, with its first revolution still uncompleted:

click map to enlarge

Tuesday, 3 December 2019

An interesting CRS-19 Falcon upper stage deorbit area (UPDATED)

click map to enlarge
The Maritime Broadcast Warnings with the hazard areas for the upcoming December 4 SpaceX DRAGON CRS-19 supply mission to the ISS have appeared a few days ago.

These include a Broadcast Warning for the Falcon 9 upper stage deorbit area. And that deorbit area (depicted in red in the map above) has an odd position and timeframe:

HYDROPAC 3933/19

DNC 02, DNC 03, DNC 04.
042302Z TO 042344Z DEC, ALTERNATE
052240Z TO 052322Z DEC
58-52S 050-29E, 55-59S 052-23E,
55-26S 059-28E, 54-58S 065-18E,
54-08S 073-22E, 52-46S 083-57E,
51-25S 091-09E, 49-01S 100-13E,
46-34S 108-49E, 44-49S 113-54E,
46-47S 116-19E, 52-02S 109-55E,
52-57S 108-32E, 56-09S 102-10E,
59-05S 092-54E, 61-08S 081-09E,
61-48S 071-27E, 61-08S 060-26E.
2. CANCEL THIS MSG 060022Z DEC 19.//

Authority: PACMISRANFAC 250217Z NOV 19.

Date: 290929Z NOV 19
Cancel: 06002200 Dec 19

With DRAGON CRS launches, the Falcon 9 upper stage deorbit usually happens in the second part of the first revolution, south of Australia or in the southern Pacific. See e.g. the deorbit area for the Falcon 9 upper stage of CRS-17 from May this year, depicted in blue in the map above.

But not this time. The Maritime Broadcast Warning above suggests that the CRS-19 upper stage deorbit happens much later, about 5.5 hours or 3.5 revolutions after launch. In addition, the area is shifted southwards compared to the CRS-19 ground track, indicating a deorbit from an orbital inclination clearly higher than the 51.6 degrees orbital inclination of the DRAGON. In fact, it fits an orbital inclination in the order of of 57-58 degrees, i.e. some 5 degrees higher in inclination.

So that is odd.

The prolonged on-orbit time might be a coasting test with an eye on future missions that require coasting over several revolutions. The indicated inclination change might likewise be a test for a future mission requirement.

I have been entertaining the possibility of an undisclosed cubesat rideshare, to a ~58 degree inclination orbit. But that remains pure speculation and is perhaps not very likely.

Note: in the map in top of this post, the dashed white line is the DRAGON CRS-19 trajectory up to 23:45 UT (Dec 4), the end of the timewindow given by the Maritime Broadcast Warning for the Falcon upper stage deorbit.

UPDATE 4 Dec 2019 10:15 UT:

During the CRS-19 pre-launch press conference yesterday, the SpaceX Director of Dragon Mission Management, Jessica Jensen, said the Falcon 9 upper stage is doing a "thermal demonstration" after the CRS-19 orbit insertion, that amounts to a six-hour coasting phase:

In reply to reporter questions she provided slightly more details somewhat later in the press conference, adding that the test is done at the request of a customer for future missions that require a long coast. During the long coast phase, they will a.o. measure the thermal environment in the fuel tanks. The apparent ~5 degree orbital inclination change was not mentioned:

Tuesday, 22 October 2019

A reanalysis of the Trident SLBM test of 10 September 2013 and other tests

9 May 2019 Trident-II D5 test launch from USS Rhode Island in front of Florida
Photo: John Kowalski/US Navy

NOTE: This post reanalyses a case from September 2013 that turned out to be a Trident SLBM test launch. New information on the launch trajectory allows to glean information on the missile's apogee. The 10 September 2013 test launch trajectory is compared to those of several other Atlantic Trident test launches in subsequent years

Elements of this re-analysis were already published in May of this year in two Twitter threads here and here. As Twitter is highly ephemeral in nature, this blog post serves to preserve and consolidate the two analysis.


On 9 May 2019, I noted a Maritime Broadcast Warning issued for the period of May 9 to 12, that clearly defined the trajectory of  a Trident-II SLBM test in the Atlantic (this was was later confirmed to be a Trident test launch from the submarine USS Rhode Island):

NAVAREA IV 394/2019 

(Cancelled by NAVAREA IV 403/2019)

   091340Z TO 120026Z MAY IN AREAS BOUND BY:
   A. 28-53N 080-01W, 29-00N 079-35W, 28-55N 078-58W,
      28-38N 079-00W, 28-40N 079-37W, 28-50N 080-01W.
   B. 28-34N 076-26W, 28-24N 075-24W, 28-10N 075-27W,
      28-21N 076-29W.
   C. 27-45N 070-22W, 27-14N 068-45W, 26-48N 068-56W,
      27-18N 070-32W.
   D. 17-46N 045-38W, 16-22N 042-18W, 15-44N 042-36W,
      17-09N 045-55W.
   E. 15-47S 004-32E, 17-17S 007-04E, 17-10S 007-08E,
      17-29S 007-49E, 17-20S 007-52E, 17-19S 008-07E,
      17-28S 008-12E, 17-41S 008-04E, 17-45S 008-14E,
      18-27S 007-50E, 17-51S 006-44E, 17-43S 006-50E,
      16-11S 004-16E.
2. CANCEL THIS MSG 120126Z MAY 19.

071718Z MAY 2019 EASTERN RANGE 071600Z MAY 19.

The five hazard areas defined in the Broadcast Warning correspond to: the launch area in front of the coast of Florida; the splash-down zones of the three booster stages;  and the MIRV target area in front of the Namibian coast. This is what it looks like when the coordinates are mapped - the dashed line in the map below is a modelled simple ballistic trajectory between the lauch area and target area:

click map to enlarge

The case brought me back six years, to September 2013, when I was asked to look at photographs made by German astrophotographer Jan Hattenbach that showed something mysterious. I suggested it was a missile test, a suggestion which was later confirmed.

In this blog post, I revisit the 2013 analysis in the light of new information about this test, and compare it to other tests for which I could find trajectory information.

In the evening of 10 September 2013, Jan Hattenbach was making a time-lapse of the night sky near the GranTeCa dome at the Roque de los Muchachos observatory on La Palma in the Canary Islands, at 2300 meter altitude.

Suddenly, a strange fuzzy objects producing cloudy "puffs" moved through the sky. I wrote about it in two blog posts in 2013 (here, and follow-up here), identifying the phenomena as a Trident-II SLBM test launch conducted from a US Navy Ohio-class submarine.

This is Hattenbach's time lapse of the phenomena: the fuzzy cloud moving from bottom center to upper left is the missile (the other moving object briefly visible above the dome is a Russian satellite, Kosmos 1410). The distinct "puffs" are likely the missile's Post-Boost Control System (PBCS) reorienting while deploying RV's during the post-boost phase:

Here is a stack of the frames from the time-lapse, and a detail of one of the frames:

click to enlarge

click to enlarge

At that time, Ted Molczan had managed to dig up a Broadcast Warning that appeared to be for the MIRV target area:

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

   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.

The case of May this year made me realize there should be Broadcast Warnings for the launch area and stage splashdown zones as well. Searching the database for such Navigational Warnings, I indeed managed to find them, as a separate Broadcast Warning:

( 082155Z SEP 2013 )
NAVAREA IV 546/2013 (24,25,26) 
(Cancelled by NAVAREA IV 546/2013)

   A. 28-57N 076-17W, 28-56N 075-54W,
      28-44N 075-11W, 28-29N 075-13W,
      28-43N 076-17W.
   B. 27-53N 073-02W, 28-14N 072-56W,
      27-58N 071-52W, 27-46N 071-08W,
      27-38N 071-11W, 27-39N 071-43W,
      27-39N 071-48W, 27-41N 072-04W.
   C. 26-42N 066-58W, 26-16N 065-36W,
      25-37N 063-38W, 25-18N 063-35W,
      25-06N 063-42W, 25-02N 063-52W,
      25-39N 065-51W, 26-07N 067-12W.
   D. 15-59N 043-47W, 16-51N 043-14W,
      15-54N 040-54W, 14-19N 038-09W,
      13-48N 038-28W, 13-30N 039-26W.
2. CANCEL THIS MSG 140230Z SEP 13.

When the coordinates of these two Broadcast Warnings are mapped, they define a clear trajectory for this test (map below). It is somewhat different from the hypothetical trajectory we reconstructed in 2013 (the launch site is at a different location, much closer to Florida) and it is very similar to that of the recent May 2019 test. The dashed line is, again, a modelled simple Ballistic trajectory between the launch area and MIRV impact area, this time fitting the hazard areas extremely well:

click map to enlarge

The trajectory depicted is for an apogee height of 1800 km. This altitude was found by modelling ballistic trajectories for various apogee altitudes, and next looking which one of them matches the actual sky positions seen in Hattenbach's photographs from La Palma best.

In order to do so, I astrometrically measured Jan Hattenbach's images in AstroRecord, measuring RA and declination of the missile in each image using the stars on the images as a reference. The starmap below shows these measured sky positions, as red crosses.

When compared to various modelled apogee altitudes (black lines in the starmap), the measured positions best match an apogee altitude of ~1800 km:

click starmap to enlarge

So, we have learned something new about the Trident-II D5 apogee from Hattenbach's La Palma observations. At 1800 km the apogee is a bit higher than initially expected (ICBM/SLBM apogees normally are in the 1200-1400 km range).

This is how it approximately looks like in 3D (green lines depict the approximate trajectories of the missile stages). The ground range of this test was about 9800 km:

click to enlarge

Out of curiosity, and now knowing what to look for in terms of locations, I next searched the Broadcast Warning database for more Broadcast Warnings connected to potential Trident-II tests. I found six of them between 2013 and 2019, including the 10 September 2013 and 9 May 2019 test launches. It concerns additional test launches in June 2014, March 2016, June 2016, and June 2018. Putting them on a map reveals some interesting patterns, similarities and dissimilarities:

click map to enlarge

The set of Broadcast warnings points to at least two different launch areas, and three different MIRV target areas.

The two launch areas are in front of the Florida coast, out of Port Canaveral. One (labelled A in the map) is located some 60 km out of the coast, the other (labelled B in the map) is further away, some 400 km out of the coast.

I suspect that the area closest to Florida is used for test launches special enough to gather an audience of high ranking military officials. The recent test of 9 May 2019 belongs into this category, as well as a test in June 2014, and also the infamous British Royal Navy test of June 2016 (I will tell you why this test has become infamous a bit later in this blog post).

As to why area A is tapered and area B isn't, I am not sure, except that the launch location for these tests could perhaps be more defined, restrained by the audience that needs a good, predefined and safe spot to view it.

Click map to enlarge

Not only are there two different launch locations near Florida, but likewise there are at least three different MIRV target areas near Africa.

Four tests, including the 10 September 2013 test imaged by Hattenbach, target the same general area, some 1000 km out of the coast of Angola (indicated as 'impact area 1' in the map below). Two of the tests however target a slightly different location.

click map to enlarge

One of these two deviating tests is the earlier mentioned infamous Trident-II test by the British Royal Navy from June 2016.

This test has become notorious because the Trident missile, fired from the submarine HMS Vengeance, never made it to the target area. Instead it took a wrong course after launch, towards Florida (!)  and had to be destroyed. That test had a planned target area (dark green in the map above) somewat shortrange from the other tests, closer to Ascension island. This is the shortest ground range test of all the tests discussed here, approximately 8900 km, some 1000 km short of most other tests. Incidently, the choice of launch area indicates this failed test had a launch audience, so I reckon some top brass was not amused that day.

The other is the recent 9 May 2019 test. This US Navy test had a target area (red in the map above) some 400 km out of the African coast, further downrange from previous tests. This is the longest range test of all the tests discussed here, with a ground range of approximately 10 700 km, about 700 km longer than the other tests. From the choice of launch area, this test too might have had a launch audience.

The other tests had a range of 9600 to 9900 km. The different ranges could point to different payload masses (e.g. number or type of RV's), different missile configurations, or different test constraints.

There have certainly been many more Trident-II tests than the six I could identify in Broadcast Warnings (e.g. see the list here). Why these didn't have Broadcast Warnings issued, or why I was not able to identify those if they were issued, I do not know.

The Trident-II is a 3-staged Submarine-Launched Ballistic Missile with nuclear warheads. The missile is an important part of US and British nuclear deterrance strategies. The missiles are caried by both US and British Ballistic Missile submarines.

click to enlarge

Edit 23 Oct 2019:
Considering the Trident-II D5 range, the US Navy clearly needs to update it's own 'fact file' here (which at the time of writing lists a maximum range of 7360 km, well short of the distances found in this analysis)

Saturday, 19 October 2019

The structure of space: orbital families

click diagram to enlarge

Asteroid observers are well acquainted with the kind of diagram above: a plot of the semi-major axis of the orbit against orbital inclination. Doing this for asteroids allows to discern resonances, and clusters visible in such a diagram point to related objects with a shared origin (asteroid 'families').

The diagram above is however not showing asteroids in heliocentric orbits, but is a similar diagram showing orbits for all 18439 well-tracked artificial objects (satellites, rocket stages and debris) in orbit around our Earth. A number of clusters can be seen: the distribution of the objects in a-i space (*) is not random but structured.

The structure corresponds to satellites with a specific purpose (and the related rocket stages and debris), or from a specific family. Some functions of satellites demand a specific type of orbit distinguishable in a-i space.

Well recognizable clusters for example in the plot above, are Geosynchronous satellites; and satellites in HEO ('Molniya') orbit. These are often communication or SIGINT satellites. NAVSTAR navigation satellites (GPS) form a recognizable cluster too.

Two loose clusters of objects can be seen that correspond to Geostationary Transfer Orbits (GTO). These are the rocket stages left from launches into Geostationary orbit. They move in eccentric orbits with low inclination. Two groups can be discerned: those launched from Kourou in French Guyana by ESA, and those launched from Cape Canaveral by NASA and NRO. The fact that these two groups group and distinguish in inclination, is because the inclination of GTO launches correlates to the latitude of the launch site.

Some clusters are debris clusters which are the result of the breakup of objects (usually exploding rocket stages) in space: two of these are indicated in the plot above.

Interesting is also the cluster that represents Earth Observation satellites in sun-synchronous Polar orbit. Let us look at this part of the plot in more detail:

click diagram to enlarge

Sun-synchronous objects are objects in orbits designed to have a rate of RAAN (node) precession that matches the precession of the sun in Right Ascension. This is beneficial to optical remote sensing observations of the earth, as it means the orbital plane moves along with the shift in Right Ascension of the sun, thus ensuring that images are made around the same solar time each day, which aids shadow analysis.

The objects in this cluster display a clear obliquely slanted trend in a-i space. This is because the sunsynchronous character of an orbit is a function of semi-major axis, eccentricity and orbital inclination. Hence, a specific orbital inclination is necessary for each orbital altitude, causing the slant in the distribution in the plot above.

[EDIT 19 oct 2019, 21:55 UT]

In the diagram below, the black line is the theoretical trend in a-i space for a circular sun-synchronous orbit. For more elliptical orbits, the slant of the line is slightly different:

click diagram to enlarge

I am not entirely sure what is behind the noticable gap visible in the distribution around inclination 101 degrees. The upper sub-cluster around 102 degrees inclination contains a number of meteorological satellites, plus debris from associated, broken up rocket stages, so it might be a sub-cluster representing a specific family of satellites

A couple of other object 'families' can be seen in this detail diagram as well, as distinct clusters. There is another breakup event visible (Kosmos 1275, a Soviet navigation satellite that disintegrated in orbit some 50 days after launch), as well as two payload families, including the Iridium satellites. The Westford Needles are tiny metal rods that are the result of a weird,  ill-conceived and eventually abandoned communication experiment during 1961 and 1963 (read more here).

* note: a-i means: semi major axis (a) versus orbital inclination (i)

Friday, 27 September 2019

Six months after India's ASAT test

Six months ago today, on 27 March 2019 at 5:42:15 UT, India conducted its first successful Anti Satellite (ASAT) Test, under the code name Mission Shakti. I wrote an in-depth OSINT analysis of that test published in The Diplomat in April 2019.

Part of that analysis was an assessment - also discussed in various previous posts on this blog - on how long debris from this ASAT test would stay on-orbit. Half-a-year after the test, it is time to make a tally of what is left and what is gone - and make a new estimate when the last piece will be gone.

A few more debris pieces have been catalogued by CSpOC since my last tally. As of 27 September 2019, orbits for 125 debris pieces from the ASAT test have been catalogued. Of these 125 objects, 87 (or 70%) had reentered or had likely reentered by 27 September, leaving 38 (or 30%) still on orbit.

click diagram to enlarge
click diagram to enlarge

Remember that the Indian DRDO had made the claim that all debris would have reentered 45 days after the test. This is clearly not correct: of the well-tracked debris for which we have orbits (presumably there is a lot more for which we have no orbits), only 29%, i.e. barely one-third, reentered within 45 days. Over 70% did not. At 120 days after the test, only half of the catalogued population of larger debris had reentered.

click diagram to enlarge
click diagram to enlarge

I used SatEvo to produce reentry estimates for the 38 objects still on orbit on 27 September 2019. By the end of the year, some 15 to 16 of these larger debris fragments should still remain on-orbit.

One year after the test, at the end of March 2020, about 90% of all tracked debris should have reentered. The last or the tracked debris fragments for which we have orbits, might not reenter untill mid 2024.

The current apogee altitudes of the objects on-orbit spread between 270 and 1945 km. They have now well-dispersed in RAAN too, no longer sharing the same orbital plane:

click to enlarge
click to enlarge

Some 90% of the debris fragments still on-orbit have an apogee altitude above that of the ISS, meaning that they almost all have orbits that reach well into the orbital altitudes of operational satellites.

Sunday, 1 September 2019

Image from Trump tweet identified as imagery by USA 224, a classified KH-11 ENHANCED CRYSTAL satellite

click to enlarge. image: US Government

The incredibly detailed image above was leaked declassified and revealed to the world by US President Donald Trump, very characteristically in a tweet, on 30 August 2019.

It shows the aftermath of the failed Iranian Safir launch of August 28/29, with considerable damage to the platform and vehicles. Obviously, there was an explosion or crash of some sort, likely an explosion of an engine or rocket stage or failed lift-off.

The image is a photograph of a printed photograph: you can see the reflection of the camera flash on the photographic print near the center of the image and the silhouet of the person photographing it. There is also some image distortion, likely because the print was curling somewhat at the edges. But the level of detail is amazing (and the original might have been even more detailed).

That level of detail quickly led to speculation: what platform took this image? A drone? A high altitude reconnaissance aircraft? A satellite?

Some initially argued that the level of detail was too high for a satellite. But as we will see in this post, it was made by a satellite, and we can even say which satellite.

The level of detail in the image is incredible and points to one of the NRO's classified KH-11 EVOLVED ENHANCED CRYSTAL electro-optical reconnaissance satellites (they are also known as ADVANCED CRYSTAL, KENNEN, and colloquially as 'KeyHole').

These are high resolution optical satellites that resemble the Hubble Space Telescope, but look down to Earth instead of to the heavens. It is known that the optics of these satellites are 2.4-meter diameter mirrors. Theoretically, from the perigee of their orbits this would yield a resolution of just under 10 cm.

Christiaan Triebert analysed the shadow directions on the image and placed the time of the image between 9 and 10 UT (August 29), or 13:30-14:30 local Iranian time. Michael Thompson pointed out on Twitter that one of the KH-11 satellites, USA 224 (2011-002A), made a pass over the launch site in that time window.

This satellite is a classified satellite, but we do know its orbit because amateur trackers track this object regularly. This is USA 224 passing over my hometown Leiden in June 2014 for example:

USA 224 passing over Leiden, 21 June 2014

This blogpost consolidates two analysis which I initially published through Twitter. I will show in this analysis that there is very little doubt that USA 224 took this image.

Matching view angles 

The map below shows how USA 224 passed almost right over the launch site at 9:43:47 UT on August 29, with a maximum elevation of 87.7 degrees. The photograph tweeted by President Trump was taken post culmination, from the location indicated by the white cross in the map above. That position is based on the analysis that now follows.

click map to enlarge

The depicted trajectory for USA 224 is based on amateur tracking data. I used elset 19239.00965638 which was ~2.5 days old at the time of the overflight. In the absence of a manoeuvre, it should be accurate to a few seconds in time along-track and very little error cross-track.

USA 224
1 37348U 11002A   19239.00965638 0.00010600  00000-0  95384-4 0    03
2 37348  97.9000 349.1166 0536016 134.6567 225.3431 14.78336728    04

The imaged launch site itself is located at 35.2346 N, 53.9210 E, altitude 936 m, and indicated by the blue dot in the map. The launch platform is part of Iran's Imam Khomeini Space Port, near Semnan.

click to enlarge. Image: US Government

Trump's image shows the platform viewed under an oblique angle, looking in a northern direction (i.e. with the satellite to the south of the site). As the launch platform is circular, we can use the ellipticity of the platform on the image to estimate the angle under which the platform was imaged. For this, we have to measure the semi-minor and semi-major axis of the ellipse (denoted Y and R in the diagram below): their ratio corresponds to the sinus of the viewing angle.

The result of this measurement is a nominal view angle of 46.03 degrees. For USA 224, this elevation with respect to the imaged site was reached at 09:44:20.7 UT (nominally), post-culmination when the satellite was to the south of the site. From the satellite ephemeris, the satellite was at an azimuth of 194.85 degrees as seen from the imaged site at that moment. The satellite's geographical position was near 33.005 N,  53.220 E at an altitude of  283 km. The range to the imaged site was 385 km.

I used these values as input in STK and simulated the view of the damaged launch platform as seen from USA 224 for 29 August 09:44:20.7 UT. The images below compare the original image from President Trump's tweet (top) and the simulated view from USA 224 (bottom):

click to enlarge

Ignoring the shadow directions, the simulated view is very similar to the actual image, pointing out that indeed the image very likely was taken by the USA 224 satellite.

(the simulated view uses an overhead commercial satellite image taken at another time, rendered to mimic an oblique view, hence the different shadow directions).

Cees Bassa, in an independent analysis, has calculated very similar figures for the viewing angle and from that azimuth and elevation.

Matching times

In a second analysis, I tried to improve on the time of the image derived from the shadow directions.

When projecting a line through the shadow of one of the masts at the edge of the platform, this line passes almost through the middle of the access road at top right in the image:

click to enlarge

I used this observation to measure the direction of the shadow in Google Earth. It corresponds to an approximate azimuth of 40.45 degrees, which would place the sun at an azimuth of about 220.45 degrees (+- 1 degree error or so):

click to enlarge

Looking this direction up in the solar ephemerids for the imaged site (calculated with MICA), this solar azimuth corresponds to 09:46:25 UT (Aug 29). This is only 2 minutes later than the time for which the image best matches the USA 224 view of the site, as reconstructed earlier in this post.

This again confirms that this image could very well have been taken by USA 224. Both the time matches, and the view matches.

With the uncertainties in the shadow direction measurement taken into account (including uncertainties introduced by possible image deformations), within error margins the two times match. The difference between the measured (~220.45) solar azimuth and the solar azimuth calculated for 09:44:21 UT is 0.85 degrees, i.e. under a degree and hence small.

The 09:44:21 UT  derived from matching the satellite view to the image, probably is more accurate than the time derived from the shadow analysis. This time is probably accurate to a few seconds, given that the satellite TLE used was 2.5 days old.


And then the baffling question: why did President Trump tweet an image that otherwise would be considered highly classified?

The KH-11 satellites are classified, and so is imagery from these satellites. If an adversary gets her hands on KH-11 imagery, it reveals information about the optical capacities of these space assets.

In 1984, a Navy intelligence analyst was sent to prison for leaking three KH-11 images to the press.

Reconnaissance satellite imagery made public by the US Government itself over the past decades were either from commercial DigitalGlobe satellites, or purposely degraded in quality such as not to reveal the optical capacities of the KH-11. But now we see a US President tweet, on what appears to be a whim for the purpose of gloating, a very detailed image that as was shown in this post definitely was taken by a KH-11 satellite.

The occassion at which this happened, is eyebrow raising. A failed space launch hardly is a matter of great geopolitical concern. It is something trivial compared to e.g. imagery showing preparations for an invasion, the production of WMD, or atrocities against humanity. The latter could perhaps be argued to be a valid reason to publish imagery that also divulges the capacities of your best space-based imaging platforms: this occasion was not.

Which makes this a rather momentous occasion.

(note: there is a black block in the upper left of the image that seems to be placed there to redact some information that might have been printed there. I think it is likely this information was the time of image, space platform ID and the location of the latter. It points out that some deliberate thought was given to the release of this image, before it was tweeted).

USA 224 passing through Corona Borealis, 17 June 2014

Edit (2 Sep 2019):

In the comments, Russ Calvert makes a very valid point: the phone camera used to photograph the photographic print might also introduce some slant. But I suspect the error introduced this way is small as normally you would try as best as you can to hold the camera perpendicular to the paper you are photographing. A clear slant angle of the camera also would introduce a sharpness gradient that does not seem to be there. The good match between the image and the simulated view from the satellite also bears out that error introduced in this way is likely small.

Edit II (2 Sep 2019): 

Added two archive images of USA 224 passing through the night sky over my hometown Leiden.

Edit III (24 Sep 2019)

Between the infamous 1984 leak by Samuel Moring Lorrison and Trumps 2019 tweet, there was one other occasion that (parts of a) full resolution KH-11 imagery became public. That was an image from the Snowden files published in September 2016 as part of an article in The Intercept,
which according to the annotations on it was taken on 28 January 2009 at 5:16 UT,

I had forgotten about it untill this article by Dwayne Day brought it to my attention again, and then I remembered that I had already identified this image as being taken by USA 129 (1996-072A), a now deorbitted KH-11 reconnaissance satellite.

image source: The Intercept 6 Sept 2016

In 2018 Bill Robinson geolocated the image as showing a part of Zaranj, a southern Afghanistan village on the border with Iran. I in turn was able to show that USA 129 was near this location (see Bill's blog post), in an appropriate position to make the image. As een from the position of USA 129 at 5:16 UT, Zaranj was located at a range of 368 km. Seen from Zaranj, the satellite was in azimuth 216 degrees, elevation 66 degrees at that time.
click map to enlarge