Monday, December 22, 2014

Analysis of the 2014-074B Soyuz r/b re-entry on 26 Nov 2014


In the early morning of 26 November 2014 between 03:35 and 03:40 UT, a very slow, long duration fireball was observed from the Netherlands, Germany and Hungary (see earlier post).

The fireball was quickly suspected to be caused by the fiery demise of a Soyuz third stage, used to launch ISS expedition crew 42, including ESA astronaut Samantha Cristoforetti, to the International Space Station on November 23.

Video still image from Erlangen, Germany (courtesy Stefan Schick)

Analysis

In this blog post, which is a follow-up on an earlier post, I will present some results from my analysis of the re-entry images, including a trajectory map, speed reconstructions and an altitude profile. The purpose of the analysis was:

1) to document that this indeed was the re-entry of 2014-074B;
2) to reconstruct the approximate re-entry trajectory;
3) to reconstruct the approximate altitude profile during the re-entry.


Data used

Three datasets were available to me for this analysis:

1) imagery from three photographic all-sky meteor cameras in the Netherlands, situated at Oostkapelle, Bussloo and Ermelo (courtesy of Klaas Jobse, Jaap van 't Leven and Koen Miskotte);

2) data from two meteor video camera stations (HUBAJ and HUBEC) situated in Hungary (courtesy of Zsolt Perkó and Szilárd Csizmadia);

3) imagery from a wide angle fireball video camera situated at Erlangen, Germany (courtesy Stefan Schick).

Some example imagery is below:


Detail of one of the Bussloo Public Observatory (Netherlands) all-sky images, courtesy Jaap van 't Leven
Detail of the Cyclops Oostkapelle (Netherlands) all-sky image, courtesy Klaas Jobse
Detail of the Ermelo (Netherlands) all-sky image, courtesy Koen Miskotte
Stack of video frames from Erlangen (Germany), courtesy Stefan Schick
Stack of video frames from HUBEC station (Hungary), courtesy Szilárd Csizmadia and Szolt Perkó

Astrometry

The Hungarian data had already been astrometrically processed with METREC by Szilárd Csizmadia and came as a set of RA/Declination data with time stamps. The Dutch and German images were astrometrically processed by myself from the original imagery.

The German Erlangen imagery was measured with AstroRecord (the same astrometric package I use for my satellite imagery). An integrated stack of the video frames resulted in just enough reference stars to measure points on the western half of the image. As it concerns an extreme wide field image with low pixel resolution and limited reference stars, the astrometric accuracy will be low.

AstroRecord could not be used on the Dutch All-Sky images because of the extreme distortion inherent to imagery with fish-eye lenses. They were therefore measured by creating a Cartesian X-Y grid over the image, centered on the image center (the zenith). Some 25 reference stars per image were measured in this X, Y system, as well as points on the fireball trail. From the known azimuth and elevation of the reference stars, the azimuth and elevation of points on the fireball trail were reduced. While obtaining the azimuth with this method is a straight forward function of the X, Y angle on the images, obtaining the elevation is more ambiguous. Based on the known positions of the reference stars and their radius (in image pixels) with respect to the image center, a polynomial fit was made to the data yielding a scaling equation that was used to convert the radius with respect to the image center of the measured points on the fireball trail to sky elevation values.

Unlike meteoric fireballs, rocket stage re-entries are long-duration phenomena. The German and Hungarian data, being video data, had a good time control. The Dutch all-sky camera data, being long duration photographic exposures, had less good time control, even though the start- and end-times of the images are known. The trails for Oostkapelle and Ermelo had no meaningful start and end to the trails. Bussloo does provide some time control as the camera ended one image and started a new one halfway the event: the end point of the trail on the first image corresponds to the end time of that image, and similarly the start on the next image corresponds to the start time of that image. There was 7 seconds in between the two images. Time control is important for the speed reconstructions, but also for the astrometry (notably the determination of Right Ascension).


Data reduction and problems

The Azimuth/Elevation data resulting from the astrometry on the Dutch data were converted to RA/DEC using formulae from Meeus (1991). For these Dutch data, the lack of time control is slightly problematic as the RA is time-dependent (the declination is not). There is hence an uncertainty in the Dutch data.

The data where then reduced by a method originally devised for meteor images: fitting planes through the camera's location and the observed sky directions, and then determining the (average) intersection line of that plane with planes fitted from the other stations, weighted according to plane intersection angle. This is the method described by Ceplecha (1987). The plane construction was done in a geocentered Cartesian X-Y-Z grid and hence includes a spherical earth surface. The whole procedure was done using a still experimental Excel spreadsheet ("TRAJECT 2 beta") written by the author of this blog, coded serendipitously to reduce meteoric fireballs a few weeks before the re-entry.

I should warn that this method is actually not too well suited to reduce a satellite re-entry. The method is devised for meteoric fireballs, who's luminous atmospheric trajectory is not notably different from a straight line (fitting planes is well suited to reconstruct this line). A rocket stage re-entering from Low Earth Orbit however has a notably curved trajectory: as it is in orbit around the geocenter, it moves in an arc, not a straight line. This creates some problems, notably with the reconstructed altitudes, and increasingly so when the observed arc is longer. Altitudes reconstructed from the fitted intersection line of the planes come out too low, notably towards the middle of the used trajectory arc. The resulting altitude profile hence is distorted and produces a U-shape. The method is also problematic when stations used for the plane fitting procedure are geographically far removed from each other. In addition, the method is not very fit for long duration events.

The data were reduced as three sets:

1) data from the Dutch stations (independent from the other two datasets);
2) data from the German station combined with the two eastern-most Dutch stations;
3) data from the Hungarian stations (independent from the previous two datasets).

Dataset (2) combines data from stations geographically quite far apart. This is probably one of the reasons why this dataset produces a slightly skewed trajectory direction compared to the other two datasets.

The Dutch images have the event occurring very low in the sky (below 35 degrees elevation for Oostkapelle and below 25 degrees elevation for Bussloo and Ermelo). The convergence angles between the observed planes from the three stations is low (14 degrees or less). This combination of low convergence angles and low sky elevations, means that small measuring errors can have a notable scatter in distance as a result.


Results (1): trajectory

reconstructed trajectory (red dashed line and yellow dots)

The map above (in conic equal-area projection) shows the reconstructed trajectory as the yellow dots and the red dashed line. White dots are the observing stations.

The thin grey line just north of the reconstructed trajectory is the theoretical ground track resulting from a SatAna and SatEvo processed TLE orbital efemerid set for the rocket stage. This expected ground track need not perfectly coincide with the real trajectory, as the orbit changes rapidly during the final re-entry phase.

The reconstructed trajectory converges towards the theoretical (expected) ground track near the final re-entry location, above Hungary, but is slightly south of it earlier in time. The horizontal difference is about 30 km over southern England, 25-20 km over northern France due south of the Netherlands, 17-16 km over southern Germany and less than 3 km over Hungary.

This difference is most likely analytical error, introduced by the low sky elevations and convergence angles as seen from the Netherlands. On the other hand, the Hungarian observations (with stations on the other, southern side of the trajectory compared to the Dutch and German stations and reduced completely independent from the other data) place it slightly south too. So perhaps the deviation is real and due to orbital inclination changes during the final re-entry phase. Indeed, a SatEvo evolution of the last known orbit suggest a slight decrease in orbital inclination over time, although not of the observed magnitude.

The results from Erlangen come out slightly skewed in direction, likely for reasons already discussed above. The Hungarian results are probably the best quality results.


Results (2): altitudes and speed

altitudes (in km) versus geographic longitude

As mentioned earlier, the altitudes resulting from the fitted linear planes intersection line come out spurious due to the curvature of the trajectory. Altitudes were therefore calculated from the observed sky elevations and known horizontal distance to the trajectory. The horizontal distance "d" between the observing station and each resulting point on the trajectory were calculated using the geodetic software PCTrans (software by the Hydrographic Service of the Royal Dutch Navy). Next, for each point the (uncorrected) altitude "z" was calculated from the formula:

         z = d * tan(h),

where "h" is the observed sky elevation in degrees.

This is the result for a "flat" earth. It has hence to be corrected for earth surface curvature, by adding a correction via the geodetic equation:

        Zcr - sqrt (r 2 + d 2)     [all values in meters],

where "r" is the Earth radius for this latitude, "d" the horizontal distance between the observing station and the point on the trajectory, and "Zc" the resulting correction on the altitude calculated earlier.

The results are shown in the diagram above, where the elevation has been plotted as a function of geographic longitude. It suggests an initial rapid decline in altitude from ~125 km to ~100 km between southern England and northern France, an altitude of ~100 km over southern Germany, and a very rapid decline near the end, with altitudes of 60-50 km over Lake Balaton in Hungary. Whether the curvature in the early part of the diagram is true or analytical error is difficult to say, although it is probably wise to assume it is analytical error.

Apart from the match in trajectory location, speed is another measure to determine whether this was the decay of 2014-074B or not. Meteors always have an initial speed larger than 11.8 km/s (but: for extremely long duration  slow meteors deceleration can decrease the terminal speed considerably below 11.8 km/s later on in the trajectory). Objects re-entering from geocentric (Earth) orbit have speeds well below 11.8 km/s, usually between 7-8 km/s depending on the orbit apogee. When speed determinations come out well below 11.8 km/s, a re-entry is a likely although not 100% certain interpretation. When speed determinations come out at 11.8 km/s or faster, it is 100% certain a meteor and no re-entry.

By taking the distance between two points on the trajectory with a known time difference, I get the following approximate speeds:

- from the Hungarian data: 7.0 km/s;
- from the Dutch data: 9.0 km/s;
- from the German data: 9.4 km/s.

These are values that are obviously not too accurate, but nevertheless reasonably in line with what you expect for a re-entry of artificial material from geocentric (Earth) orbit.

It should be noted that if the southern deviation (see trajectory results above) of the trajectory data is analytical error, the speed of the Dutch and German observations is a slight overestimation, while the Hungarian results will be a slight underestimate. This would bring the speeds more in line with each other, and even closer to what you expect from a rocket stage re-entry from Low Earth Orbit.


Discussion and Conclusions

The trajectory and speed reconstructions resulting from this analysis strongly indicate that the fireball seen over northwest and central Europe on 26 November 2014, 03:35-03:40 UT indeed was the re-entry of the Soyuz  third stage 2014-074B from the Soyuz TMA-15M launch. Although there are some slight deviations from the expected trajectory, the results are close enough to warrant this positive identification.

The deviations are easily explained by analytical error, given the used reduction method and the not always favourable configuration of the photographic and video stations with regard to the fireball trajectory. Notably, the large distance of the Dutch stations to the trajectory resulting in very low observed sky elevations and low plane fitting convergence angles for these stations is a factor to consider. Nevertheless, and on a positive note, the final result fits the expectations surprisingly well.

The data suggest that the object was at an altitude approaching 125 km (close to the expected final orbital altitude on the last completed orbit) while over southern England and the Channel, had come down to critical altitudes near 100 km while over southern Germany, and was coming down increasingly fast at altitudes of 60 km and below while over Hungary.

The Hungarian observations show that the rocket stage re-entry continued beyond longitude 19.3o E and below 46.45o N, and happened some time after 03:39:20 UT. It likely not survived much beyond longitude 21o E.

The nominal re-entry position and time given in the final JSpOC TIP message for 2014-074B are 03:39 +/- 1 min UT and latitude 47o N longitude 17o E, with the +/- of 1m in time corresponding to a +/- of several degrees in longitude. This is in reasonable agreement with the observations.

Acknowledgements

I thank Zsolt Perkó, Szilárd Csizmadia, Stefan Schick, Jaap van 't Leven, Klaas Jobse and Koen Miskotte for making their images and data available for analysis. Carl Johannink contributed some mathematical solutions to the construction of the spreadsheet used for this analysis.

Note: another Soyuz rocket stage re-entry from an earlier Soyuz launch towards the ISS was observed from the Netherlands and Germany in December 2011, see earlier post here. As to why it takes such a rocket stage three days to come down, read FAQ here.



Literature:
- Ceplecha Z., 1987: Geometric, dynamic, orbital and photometric data on meteoroids from photographic fireball networks. Bull. Astron. Inst. Czech. 38, p. 222-234.
- Meeus J. (1991): Astronomical Algorithms. Willmann-Bell Inc., USA. 



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Thursday, November 27, 2014

[UPDATED] Re-entry of Soyuz third stage 2014-074B from Soyuz-TMA 15M launch observed from the Netherlands and Hungaria.

Update 23 Dec 2014: further analysis of imagery in new post
(28 Nov 2014, 10:45 UT: updated with more imagery)

click image to enlarge

Today Carlos Bella alerted the seesat list that Hungarian amateur astronomers had captured imagery of a re-entry in the early morning of November 26.

It concerns the re-entry of 2014-074B, the Soyuz third stage from the launch of Soyuz-TMA 15M which launched expedition crew 42 to the ISS on 23 November 2014.

Below is one of several casual phone-camera video's also shot from Hungaria Serbia, showing the fragmenting fireball:


(video by Aleksandar F, Belgrade)

According to the TIP message of  JSpOC, the re-entry happened near 3:39 UT on the early morning of 26 November, 2014, near 47 N,  17 E. This perfectly fits the Hungarian observations. See also the map above, which shows the predicted trajectory of 2014-074B resulting from processing the last known orbital elements with SatAna and SatEvo.

Moreover, the speed determination by the Hungarian meteor camera network, 7.4 km/s, confirms this is not a meteor but a re-entry. The speed is too low for a meteor (which are always faster than 11.8 km/s, the earth escape velocity) but matches the speed of an object re-entering from Low Earth Orbit.

Realizing that the rocket stage made a pass over the Netherlands/Belgium only minutes earlier,  I asked the operators of the DMS All-Sky meteor cameras to check their imagery of that morning. As it turns out, three Dutch All-sky stations did capture the re-entry: Bussloo (Jaap van 't Leven), Oostkapelle (Klaas Jobse) and Ermelo (Koen Miskotte).
 
Detail of the Bussloo Public Observatory all-sky image (courtesy Jaap van 't Leven)

Detail of the Cyclops Oostkapelle all-sky image (courtesy Klaas Jobse)

Detail of the Ermelo image (courtesy Koen Miskotte)

Parts of the three Dutch images (courtesy Jaap van 't Leven, Klaas Jobse and Koen Miskotte) are shown above. All stations have it very low above the horizon at elevations of 20 degrees or lower.

The Oostkapelle image shows that the incandescent phase of the re-entry already started over the UK, as the image shows the trail well to the west (and Oostkapelle is on the Dutch West coast).

As soon as I can find some time, I will analyze the imagery to see whether I can get altitude data from them. It would be nice to document the last minutes of this rocket stage in this way!

So stay tuned for an update....

UPDATE 23 Dec 2014: new post with a further analysis with trajectory and altitude reconstructions based on observations from the Netherlands, Hungaria and Germany now available

(I thank Jaap van 't Leven, Klaas Jobse and Koen Miskotte for permission to use their imagery)

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Monday, November 10, 2014

Live blog from ESOC, Darmstadt: Philae (Rosetta) Landing on comet Churyumov-Gerasimenko:

 LIVE BLOG

 
I (am) was on-site at ESA's European Space Operations Center (ESOC) in Darmstadt for the Philae landing on comet 67P/Churyumov-Gerasimenko
This blog-post will be live updated as the events unfold. 
Be sure to hit refresh upon a new visit!
 I will also  be tweeting through @Marco_Langbroek)

15 Nov

01:45 The communications link has broken. This is it. Philae has gone to sleep, perhaps to never wake up again...or will it? So far it has kept amazing us all, after all...!

01:29 Philae has been switched into standby mode. All instruments powered off, but communications llink still active. Time to go to sleep now, brave little friend....

01:00 Battery power is dropping fast but Philae is not giving up! More and more data is being received. This is History written large, with a capital H. Truely epic science History!

00:28 Philae's rotation, over 35 degrees, was successful.
https://twitter.com/philae2014/status/533393729156308992

00:20 Philae is alive and the drill has worked! At the moment, they are trying to rotate the lander to get more sunlight on the panels. I think we can safely say now that nothwithstanding all that went different from what was planned, the mission has become a resounding success!

14 Nov

15:10 Brief recap of the Google+ briefing of this afternoon: Matt Taylor apologizes for #shirtgate. Contacts Rosetta-Philae are very stable. 80% of the most important science data from the first science sequence are now in. Rosetta has not imaged Philae on the surface yet, but there are still images in the pipeline and the search continues.  Holger Sierks suggests that in fact, they should have caught the lander just before touchdown at 500 meter above the surface, and during the first bounce in the images from the first two hours after touchdown, which have not been downloaded yet. These images should give the direction of the rebounce.
Lomatsch told that Philae has not moved at all since finally settling. Philae is in a difficult position however, surrounded by walls, limiting sunlight reaching the solar panels.From what she said, I get the impression that hopes for a lander revival once 67P/ is closer to the sun, should not be too high.
During the Q&A Ulamec indicated that it is unlikely that cometary jets will blow the lander from the surface as activity increases, as it has a too high density.
The DS2 drill is already extended 25 cm below base plate, but as there is a (scheduled) loss of contact right now, it is unsure whether it can/has reached the surface yet. New (and perhaps last) contact with Philae near 22 CET this evening. A command to go into low power mode did however not reach Philae, so it is going to get really close wether the next contact will be successful.


9:55 Philae's batteries will run out of power tomorrow. Coming night the operators will try to rotate the lander such that the largest solar panel will be facing the sun (via @elakdawala)https://twitter.com/elakdawalla/status/533179905610371073

4:55 Although it will be under "very risky conditions", SD2, the core drilling tool, will be employed. it will take subsurface samples that will be analysed by COSAC and Ptolemy, two instruments that o.a. look for organic compounds and determine the isotopic composition of water in the comet. The latter will yield information whether water may have been brought to Earth by comets.
https://twitter.com/rosettasd2/status/533056385819607040

00:45 MUPUS is communicating the first "science" temperatures (but not subsurface yet) https://twitter.com/philae_mupus/status/533040327058534400

13 Nov

23:25 After first attempt failed, second upload attempt of MUPUS commands succeeded!
https://twitter.com/philae_mupus/status/533021560593219584

21:58 The commands to deploy MUPUS failed to upload: https://twitter.com/philae_mupus/status/532998982193397762

20:55 Tonight the MUPUS  (MUlti-PUrpose Sensors for Surface and Sub-Surface Science) instrument will be deployed, for about 20 cm of its 30 cm length. The probe, which contains several temperature sensors, will be slowly hammered into the subsurface. The goals are amongst others to gather data on subsurface consistency, and a subsurface temoperature profile. It also provides calibration data for the thermal mapper onboard the Rosetta orbiter. 

    19:40 More details have been released. Philae bounced twice, at 15:34 GMT (first contact of lander with comet) and 17:25 GMT, before settling on the cometary surface at 17:32 UT. It rotated around the Z-axis (the vertical axis) after the first bounce (this rotation was the first sign yesterday evening that the lander did not settle at first contact). It is working though, although there are indications that some of the solar panels are in shadow (perhaps due to a nearby boulder? [update: it's a cliff]). It hence does not have full power. 

    So that first bounce took two hours, while the second bounce appears to have been mild. As the harpoons did not work, Philae is not well anchored to the comet. This will interfere with some of the planned activities (e.g. coring the subsurface).

    See also: http://blogs.esa.int/rosetta/2014/11/13/philae-the-happy-lander/

    17:20 (This post comes belated as I am still travelling homewards...)
    ESA has released the first panoramic image by Philae. It is obviously a rather dark world out there... Of all the extraterrestrial landscapes imaged, I feel this one beats them all! This truely is a Primeordial world... (photo: ESA)



    16:30 (back on Dutch soil, but stil in the train) The place where Philae finally landed has been located. It is about 1 km offset from the original location. In the image below, the cross is the original landing site, the box where it finally ended up.


    (image: ESA)

    12:05 News now is that Philae is on the comet, but not anchored well. This means the coring of the subsurface cannot happen, which is a bummer. Still, no doubt much new scientific data will be gathered. Given that we knew this landing effort was very risky, we can say Philae is a big success anyway!

    I am at Darmstadt railroad station currently, about to return home to the Netherlands, so this will be my last blog update today for now.

    11:50 CET  Great news! Philae is alive and has send the first images of the comet' surface!
    below you can see one of the lander legs, and part of the surface. The image is a composite of two images taken by Philae's CIVA camera.



    Image : ESA


    12 Nov

    20:25 Gist of the press briefing: some data might indicate that Philae briefly left surface again after touchdown, i.e. it bounced and then settled again at a slightly different spot. Data need to be evaluated now. Next briefing is tomorrow 14:00 CET. No word about those images shown by the French...

    19:10 This is reportedly the first image of the comet's surface (but image is unconfirmed, at least it has not been shown yet here at ESOC):



    18:12 Ulamec just told reporters that a lot is still uncertain about the spacecraft condition and safety. Also said option to try to re-fire harpoons is risky, as the non-working gas thruster cannot produce the counterforce necessary. This mean the counterforce of (re-) firing the harpoons could result in Philae being ejected from the comet surface.

    17:42 Flight controller Geurts reports that the gas thruster indeed did not work, and that the anchors did not fire. Incredible that the landing nevertheless still seems to have been succesful!
    Geurts mentioned they might retry to fire the anchors.

    17:04 Philae has landed!!!!! They are receiving telemetry. Harpoon has been fired, landing gear is in. Its on the surface!!!!

    16:50 Nailbiting at ESOC!



    16:28 Touch down window has started.....fingers crossed!

    15:52 https://twitter.com/spaceflight101/status/532546694593126400 cool image of Philae on its way down as imaged by the Rosetta orbiter! note the three extended landing legs.
    Think about what this image exemplifies: To boldly go where no-one has gone before! Exploration!



    15:18 Image of Rosetta imaged by Philae has been shown now. Descend so far is "going as planned". Image is here:  https://twitter.com/esa_rosetta/status/532537918557265921

    12:33 Deployment of Philae landing gear confirmed.

    12:07 Datalink Philae-Rosetta confirmed! Datalink with both objects is healthy. This is an important moment! Over the next hours Philae data from the descend phase will be relayed to the control center. In about 5 hrs from now, Philae should touch down.

    11:00 My ESOC source tells me that for the cold gas thruster to work, a membrane was to be punctured. And this might actually have happened, but the returned sensor data that should confirm this was "contradictory". So the system might actually work, but it is not certain.

    10:20 First data relay from the still descending lander expected about 2 hours from now. Telemetry plus a picture of th orbiter seen from the lander. The lander will reach the cometary surface in about 7 hours from now. The big wait has started.....

    10:20 Dr Churyumov:


    10:04 Separation confirmed!!! Alea Jacta est, to quote old Julius

    9:50 Matt Taylor: "This is our Longest Day" 

    9:36 Separation of the lander is actually happening now, but we won't know for a while as it takes the confirmation signal 28 minutes to reach us

    9:30 The problem with the cold gas system means they have to land without it. This introduces the risk that the lander will bounce back from the cometary surface because of opposite forces when they fiire the anchor harpoon.

    8:15 We have a GO!

    8:00 CET - The go/no of last night has been delayed. The cold gas sytem of Philae has a problem. This cold gas drives the small thruster on top of Philae that pins the lander to the comet surface in the first few minutes.

    11 Nov - The go/no go decision of this evening has given a 'go' as verdict. Early tomorrow morning there will be a second, and last, go/no go moment.




     (player provides a live stream from ESOC by ESA)

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    Announcing a Live Blog from ESOC during the Philae landing on 67P/Churyumov-Gerasimenko

    On Wednesday November 12, Philae, the lander of ESA's Rosetta mission, will attempt to land on comet 67P/Churyumov-Gerasimenko.

    I will be at ESA's Space Operations Center ESOC when this happens. If the WiFi doesn't fail on me, I will attempt to live-blog the events of that day on this blog, as well as live tweet the events via my Twitter account (@Marco_Langbroek).

    So stay tuned here (or on Twitter) next Wednesday!

    Meanwhile, here is a nice interactive 3D model (model courtesy of ESA) of the comet to play with (requires WebGL enabled browser: might not work in iOS):


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    Saturday, November 01, 2014

    Brightness variation of the USA 198 Centaur rocket stage on October 30, 2014

    Earlier today I posted this image of the USA 198 Centaur rocket (2007-060B) passing close to M33 galaxy in Triangulum:

    click image to enlarge
    I noted a slight but clear brightness variation in the trail segments on subsequent images (the stack above is a stack of 19 individual images). I therefore decided to use the images to create a brightness variation profile.

    click diagram to enlarge

    The result is the diagram above (grey crosses are individual pixel values; the blue line is an 11-point sliding average; the red dotted line a sinusoid with a period of 37 seconds). This is the result of combining measurements of the trail brightness variation on 20 images. The individual pixel values are noisy, the result of using a high ISO setting of 2000 (which results in noise) but a pattern is visible, even more so in the 11-point sliding average.

    The diagram shows a modest but clear semi-regular brightness variation with a peak in brightness approximately each 37 seconds. There is perhaps also a regularity visible in that each second valley in the curve is more shallow than the first. The pattern suggests a slow tumbling motion.

    Below is one of the original individual images:

    click image to enlarge

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    USA 198 r/b passing the M33 galaxy

    click image to enlarge


    Last Thursday evening was very clear. I tested a clip-in CLS filter on my Canon EOS 60D, employing the 2.8/180mm Zeiss lens and a motorized tracking mount.

    One of the targets was M33, a big galaxy in Triangulum. As it happened (it was not planned), I captured a classified object in the series: the USA 198 r/b (2007-060B). It can be seen passing M33 in the image above, which is a stack of several 20-second images (breaks in the trail represent short moments inbetween consecutive exposures).

    As the images do not have the timing accuracy of my usual tracking images, they are probably of little use for astrometry. But I do seem to see some slight brightness variation, so I might try to construct a brightness curve.

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    Sunday, October 19, 2014

    Imaging the North Korean Kwangmyŏngsŏng (KMS) 3-2 satellite

    Yesterday evening was initially clear. Using the SamYang 1.4/85 mm lens, I imaged an object that has been on my "to do"-list for a (too) long time: the North Korean satellite Kwangmyŏngsŏng 3-2 (KMS 3-2, 2012-072A), visible as a very faint trail on this image:

    click image to enlarge

    Kwangmyŏngsŏng ("Brilliant Star") 3-2 was launched under much international tension almost two years ago, on 12 December 2012, from Songhae. It is the first and so far only successful North Korean launch.

    On 8 Dec 2012, just days before they launched KMS 3-2, the N-Koreans actually visited this weblog, looking for information on US IMINT satellites (specifically Lacrosse and Keyhole). As I wrote at that time, very few North-Koreans have access to the internet. Those who do, have close ties to Kim Jung Un or are among the top military. So that visit was surprising.

    The reason became quickly apparent. Post-launch, I made an analysis of the KMS 3-2 launch time, showing that the North Koreans picked a carefully determined one-hour gap in Western space-based IMINT coverage to launch their satellite.

    Later that month, on 21, 22 and 23 Dec 2012, the North-Koreans popped up again, visiting my launch time analysis post, and searching for TLE's of their own satellite! (one would expect that the Chinese could provide these to them, so this was surprising again). The visits came from another IP than the Dec 8 visits.

    Another visit to this blog was made two weeks later, on 8 Jan 2013, from the same IP as the Dec 8 visit (but another computer perhaps, as the Dec 8 visitor used Windows Xp, but this visitor Windows 7). This time the subject of the visit was my analysis of the tumbling behaviour of the satellite which I made late December 2012 using Greg Roberts' 20 Dec 2012 footage of a KMS 3-2 pass (as it was in the dead of the Northern hemisphere winter, it was not possible for me to image the satellite myself at that time). They might have been interested in my analysis in order to assess the character of this tumbling, which was probably not intended and might indicate a failure to stabilize the satellite after orbit insertion.

    Then it was quiet for 1.5 years. But last summer, I got another surprise N-Korean visit to this blog. This happened on June 9, and it was this visit which reminded me that it might be fun to try to image the satellite this summer. For various reasons, I only succeeded last night.

    The June 9 N-Korean visitor visited posts about the SDS and SBSS satellite systems. The first (SDS, Satellite Data System) is a system of geostationary US military data relay satellites which (a.o.) relays IMINT data from other satellites to the US. The other (SBSS, the Space Based Space Surveillance system) is a satellite in Low Earth Orbit for detecting and tracking objects orbiting in space (i.e., other satellites - like those of North Korea).

    This visit came while upgrade activities of the launch installations at Sohae were documented by the 38 North blog. The upgrade seems to point to Sohae being readied to facilitate a heavier launch vehicle. How a North-Korean interest in SBSS and SDS would fit into this picture, is however not entirely clear, apart from that it could indicate that they might aim to avoid SBSS tracking of their payloads during the initial orbit insertion.

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    Sunday, September 28, 2014

    Observing HEO objects

    Friday evening I missed the LEO window because of a dinner. When back home near midnight, conditions were dynamic: intermittent clear skies and roving cloud fields.

    A HEO (Highly Elliptical Orbit) object called "Unknown 051230" (2005-864A) was well-placed near the zenith, in Cepheus. I targetted it using the 2.8/180mm Zeiss Sonnar MC lens, snapping pictures during clear spells. It shows up well, as a tiny but clear trail (indicated by the arrow in the image):

    click image to enlarge

    This object is one which our analysts cannot link to any particular launch - hence the designation "Unknown". It is being tracked by us for quite a couple of years now (since Greg Roberts discovered it on 30 December 2005). It could be either a (defunct) payload, or an old rocket booster.

    At the time of my observations it was at an altitude of 36650 km, close to its apogee, situated over the Arctic circle roughly above Iceland:


    orbital position of Unknown 051230 at the time of observation
    click image to enlarge

    Nadir view from orbital position of Unknown 051230 at the time of observation
    click image to enlarge

    Highly Elliptical Orbits (also called a Molniya orbit) typically have an orbital inclination near 63.4 degrees, an apogee near 36000 km, and perigee at only a few hundred km altitude, usually over Antarctica.

    63.4 degree orbital inclination of Unknown 051230
    click image to enlarge

    The ~63.4 degree inclination with these orbital parameters ensures that the perigee is stable, i.e. always stays over the southern hemisphere.

    An object in this orbit has a period of 0.5 day, so it makes 2 revolutions per day. Its residence time in perigee over the southern hemisphere is only brief: most of the time it is at high altitude over the northern hemisphere, allowing many hours of  continued presence above that area (see image above).

    Objects in these orbits are therefore typically used to provide communications at high Northern latitudes, or for SIGINT and infra-red surveillance.

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    Tuesday, September 23, 2014

    USA 186, bright and fast

    USA 186 (top) and an old Russian r/b (1988-039B, lower corner)
    click image to enlarge

    Yesterday evening at the end of twilight, I observed USA 186 (2005-045A) pass amidst some scattered clouds. It had cleared just in time.

    Close to perigee, the satellite was moving fast. At 70 degrees elevation due East, it became bright (about mag. +1.5), and then briefly flared to mag -1 near 19:06:20 UTC (22 Sep).

    A second bright object was moving lower in the sky, and slower. It was an old Russian rocket from the Kosmos 1943 launch in 1988, 1988-039B.

    Unfortunately, it later became completely clouded, so I missed this morning's favourable pass of the ISS and Dragon CRS-4, just hours before berthing.

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    Saturday, September 20, 2014

    USA 186 manoeuvered on the 17th

    USA 186 being half a minute late one hour after the manoeuvre, 17 Sept 2014, 19:32:02 UT.  Chinese satellite Yaogan 11 also visible  (click image to enlarge)


    Ten days after the first post-summer-glareout observations of the KH-11 Keyhole/CRYSTAL optical reconnaissance satellite  USA 186 (2005-042A), it has made another orbital manoeuvre.

    In the evening of Wednesday 17 September I was targetting the satellite in a somewhat hazy sky, using the 1.4/85mm lens and a FOV near the tip of the Big Dipper tail.

    To my surprise, the satellite was over half a minute late with respect to a 3-day-old element set. This suggested a  manoeuvre. My observations were corroborated by video observations of Leo Barhorst in the Netherlands and visual observations by Pierre Neirinck in France, obtained during the same pass.

    The image above shows one of my images. As it turns out, this image was taken perhaps only an hour after the manoeuvre! USA 186 is overtaking Yaogan 11 (2010-047A) in the image (the fainter shorter, upper trail). Yaogan 11 is a Chinese optical reconnaissance satellite.

    Observations the following evening by Cees Bassa and me in the Netherlands showed the satellite running even more late by that time: it passed 6m 32s late, low in the west. My camera caught it very close to the image edge. A few hours later, Kevin Fetter in Canada captured it as well.

    The Sept 17 and 18 observations suggest that the manoeuvre happened on Sept 17, just before I did my Sept 17 observations (perhaps only an hour before, i.e. less than one revolution!). The current orbital solutions vary a bit between analysts (the post-manoeuvre observational arc is still short), but they agree in that the manoeuvre slightly adjusted the inclination, raised perigee and lowered apogee.

    The new orbit is sun-synchronous and close to a 321 x 417 km orbit (it was 265 x 440 km before the manoeuvre), i.e. perigee was raised by about 55 km and apogee lowered by about 23 km. The new orbit is more circular, and starts to conform to the orbit I envisioned in October 2013. I suspect more manoeuvres gently raising perigee and lowering apogee until an approximate 390 x 400 km orbit is reached will occur over the coming half year.

    An analysis using COLA suggests the manoeuvre(s) occured on 17 September, either near 17:46 UT or 18:25 UT. Or perhaps (and I favour that) it was a double manoeuvre, performed near both of these moments.

    17:46 UT corresponds to passage through the ascending node on the equator, only minutes after passing through perigee. 18:25 UT corresponds to passing through apogee.

    A manoeuvre to change inclination is normally done in one of the orbital nodes, or near the poles. A manoeuvre to raise or lower perigee is normally done while the satellite passes through it's apogee, and a manoeuvre to raise or lower apogee is normally done in the perigee. If either one of these (in the current case: the perigee) closely coincides with passage through one of the nodes, this is the ideal moment to change both peri- or apogee, and the inclination in one boost, which spares fuel.

    It is very difficult to  adjust the inclination, change the apogee altitude and change the perigee altitude in one manoeuvre.

    My favoured scenario is therefore that a first manoeuvre happened near 17:46 UTC in or near the ascending node (and near perigee). This lowered the apogee altitude from 440 to 417 km, and allowed a slight adjustment of the inclination at the same time. Half a revolution later, while passing through apogee near 18:25 UTC, a second manoeuvre was made to raise the perigee altitude from 265 to 321 km.

    (click map to enlarge)


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    Monday, September 15, 2014

    Rosetta's landing spot. In 3D. Woah!

    image: ESA

    Put on your red-cyan glasses and take a look at the image above (high-res here on the ESA website). It is the chosen landing site of Rosetta's Philae lander on comet 67P/Churyumov-Gerasimenko. Woah!

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    Saturday, September 13, 2014

    KH-11 USA 186 has stabilized its orbit

    Note 15/09/2014 9:25 UT: corrected inadvertent apogee - perigee mix-up in 4th paragraph
    USA 186 passing in early twilight of the evening of Sept 12, 2014
    (click image to enlarge)

    At the end of May, Northern hemisphere observers lost visibility of KH-11 Keyhole/CRYSTAL USA 186 (2005-042A) when the midsummer nights became too short. The orbital plane of the satellite was still drifting at that time, a process that started after a manoeuvre in mid-November 2013 (see earlier posts on this blog). The big question was, when that drifting would stop. I expected that when the satellite reached its new intended orbital plane it would manoeuvre into a stable sun-synchronous orbit again.

    It now has done so, having manoeuvered probably on or near July 1. The orbital plane drift has stopped.

    Kevin Fetter in Canada made a chance recovery of the satellite, the first post-summer glare-out sighting, on September 8: he was looking for another object and saw a "unid" in Low Earth Orbit pass through his field of view, that Cees Bassa was quick to identify as USA 186, in a new orbit. Over the next nights several other observers tracked it (including me on Thursday and Friday evening) yielding a first version of the new orbit it is in.

    USA 186 passing close to Arcturus (top left) in the evening of Sept 11, 2014
    (click image to enlarge)

    The satellite has drastically lowered its perigee apogee by almost 500 km, and gently raised its apogee perigee by a few km. It is now in an approximately 265 x 440 km, 96.9 degree inclined orbit. This orbit is sun-synchronous again.

    This means that the RAAN drift relative to the other satellites in the KH-11 constellation that had been going on since mid-November 2013, has stopped. It has finally settled at a RAAN distance of about 25 degrees from USA 245 (2013-043A), the primary West plane KH-11.



    Comparing the new orbit to the old orbit suggests that the manoeuvre into the new orbit happened on or near July 1st.

    In all, the satellite has kept itself pretty much to the expected scenario which I outlined on this blog in several posts in September and October 2013, e.g. here and here. Following the launch of USA 245 (2013-043A) into the primary West plane of the KH-11 constellation in August 2013, I had predicted that:

    1) USA 186, at that time the primary West plane satellite, would migrate its orbital plane to the secondary West plane; 
    2) USA 129, the extremely aged satellite in the secondary West plane, would be de-orbitted;
    3) after a period of drifting, USA 186 would manoeuvre back into a sun-synchronous orbit again, stopping the RAAN drift, when reaching the intended plane location of the secondary West plane;
    4) that in that manoeuvre it would drastically lower its apogee from near 1000 km to near 400 km and gently raise its perigee.

    This all has basically happened. It differed on details with my predictions, but the bigger picture is pretty much as I anticipated.

    What was somewhat unexpected, is that the satellite had its RAAN drift to a much larger distance with respect to the primary West plane (now occupied by USA 245) than I had anticipated. I expected 10, maybe 20 degrees. It turned out to be almost 25 degrees.

    The perigee, although indeed raised, is slightly lower than I expected. The massive lowering of the apogee is exactly how I expected it to be however.

    The current orbital plane makes it make passes near 8 am and 8 pm local time.

    Meanwhile, there are indications that USA 245 (2013-043A) in the primary West plane has manoeuvered. Russell Eberst still observed it in it's last known orbit from Scotland on Sep 7. Then Bjorn Gimmle from Sweden observed an unknown object on Sep 10, that I suspect is USA 245 after a perigee raising orbital manoeuvre conducted between Sep 7 and Sep 10.

    [note 14/09/2014: Mike McC identified Bjorn's object as a Russian r/b near decay]
    [note 15/09/2014 9:25 UT: corrected inadvertent apogee - perigee mix-up in 4th paragraph]

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    Thursday, September 11, 2014

    [Updated] You Only Die Twice: the confusing end of the Russian Kosmos 2495 Kobalt-M spy satellite mission

    Update 15:00 UT, Sep 11: a very brief update confirming the object was artificial is provided at the end of this post

    Introduction: a spectacular fireball over the USA on September 2-3

    In the evening of September 2 (in local time: early September 3 in UT), 2014, a spectacular event was seen and filmed in the skies over the southwestern States of the USA. A very slow fireball crossed the skies, seen by many casual eyewitnesses in several US States who reported their observations to the American Meteor Society (AMS). It was also captured by a number of all-sky video stations. A very nice compilation of images and what is known and what is still debated, has been made by Spaceflight101 on their website. Below is imagery of the event by Thomas Ashcraft from near Lamy, New Mexico:



    video footage  by Thomas Ashcraft, New Mexico, USA


    The event happened on September 3, 2014, between 4:31-4:33 UT (the evening of September 2 in local time) and was seen from Colorado, Wyoming and New Mexico. A very slow fireball, with a duration of at least 40 seconds and variable in brightness in what looks like a semi-regular pattern, moved across almost 180 degrees of sky. It penetrated deeply into the atmosphere, leaving a debris cloud at low altitude lingering for 30 minutes, detected by Doppler weather radar.

    Lingering debris cloud on Doppler radar after the event (image: Rob Matson)

    Initially seen as a meteor event, it was somewhat ignored by the amateur satellite community until brought to their attention a few days later.

    Suspicion of a satellite re-entry

    The suspicion arose that this was in fact a satellite re-entry, with the prime candidate being Kosmos 2495 (2014-025A), a Russian Kobalt-M/Yantar 4K2M photoreturn spy satellite. This is a satellite that uses analogue film rather than electronic image sensors. The exposed film is returned to earth in three recoverable return capsules, the last of which also returns the camera (for re-use).

    In terms of duration, the September 2-3 event is a borderline case: with a duration of at least 40 seconds but possibly a minute or more, both a very slow 11.8 km/s meteoric fireball of asteroidal origin, or the decay of an artificial satellite are possibilities. [but see update at the end of this post: NASA camera data show it was not a meteor but an object entering from Low Earth Orbit, i.e. a satellite]

    Timing and path over the sky however closely match predictions for Kosmos 2495. The observed object passed only ~3 minutes earlier than the predicted pass of the satellite, in a very similar trajectory. This actually fits with a decay, as in a lower orbit the object starts to slightly speed ahead of an object in a similar but higher orbit. The slight eastern displacement of the sky track also fits with this: in a few minutes time, the earth rotates under the orbital plane slightly, displacing the sky track westwards.


    Predicted Kosmos 2495 sky trajectory for Thomas Ashcraft's site in Lamy, New Mexico. Note remarks in text about slightly eastward displacement of trajectory for a slightly earlier passing object in the same orbital plane, relative to the sky trajectory shown here
    (click image to enlarge)

    As this satellite should have been in earth shadow at that time of the event and hence not illuminated by the sun, it is immediately clear that if this was Kosmos 2495, it was in the act of re-entering and already producing a plasma envelope (a fireball).

    [paragraph slightly rewritten 12:10 UT, Sep 11]
    But why? The last known orbital element set for the satellite with epoch 2 Sep 17:12 UT show it at an orbital altitude too high for an imminent natural decay.

    JSpOC however issued an "administrative decay" for the satellite early on September 3, an indication that it has been deliberately de-orbited.

    Yet it was unlikely that the Russian military intended this satellite to re-enter over the USA  instead of over Russia itself, or over the Pacific.

    So, if this was Kosmos 2495, did something go wrong? It initially looked like it.

    Then came the confusion

    Then came the confusion. On the Seesat-list, Ted Molczan reported having received reports of sightings of a re-entry earlier that same day, near 18:14 UT on September 2, seen over southwest Kazachstan. A number of video's exist of this event and show a glowing object followed at some distance by a cloud of glowing fragments.



    footage from Kazachstan

    The location of these observations, timing and general direction fits well with an object on a trajectory to Orenburg in Russia, the designated touchdown locality of the Kobalt-M re-entry capsules. Indeed, the timing of the observations (~18:14 UT) matches a pass of Kosmos 2495 over the area, and the trajectory of the latter indeed brings it over Orenburg near that same time.

    So if this was the Kosmos 2495 re-entry over southwest Kazachstan and the Kaspian sea, then what was it that re-entered over the USA 10 hours later?

    In denial

    Next, the Russian military weighed in and flatly denied that anything went wrong with Kosmos 2495, implicitly suggesting that the object decaying over the USA was not their satellite (spoiler: it nevertheless likely were parts of the satellite, see below).

    Multiple parts

    For a solution of this confusion, we have to look at the construction of a Kobalt-M satellite, and previous Kobalt-M missions. An excellent and detailed description of the Yantar/Kobalt satellites translated from a Russian publication can be found here on Sven Grahns website.

    We have to realize that the Kobalt-M satellites are made up of multiple modules:

    1) The Equipment Module (AO) that contains the main power and propulsion systems;
    2) The Instrument Module (PO) that contains electronic equipment necessary for the control and functioning of the satellite;
    3) The camera re-entry vehicle (OSA), containing the camera and the last batch of film. This is a true re-entry vehicle, designed to survive re-entry through the atmosphere for recovery of the camera and film. The target area for these re-entry vehicles is near the Russian town of Orenburg;
    4) a 2.5 meter sun shade with additional antennae and sensors on the tip of the OSA, that is presumably jettisoned at re-entry.

    The satellite also has two additional small re-entry and landing capsules for the recovery of film mounted on the side of the OSA: these are jettisoned for re-entry at 1/3rd and 2/3rd into the mission, so should no longer have been present on Kosmos 2495 on September 2.

    Of importance is that the OSA re-entry module eventually separates from the satellite for re-entry. This potentially leaves satellite parts in orbit after the OSA re-entry, even though it is generally believed that the AO and PO go down with the OSA, with the AO providing the retrofire burn for the de-orbit of the OSA.

    Re-entry of the Kosmos 2495 OSA return vehicle observed over Kazachstan towards Orenburg at 18:14 UT, Sep 2

    The event seen from Kazachstan was, given the location and timing, most likely the OSA return vehicle with the camera and film re-entering the atmosphere for recovery at Orenburg. The single object in front visible in the videos is likely the returning OSA itself. The cloud of fragments at some distance behind it, might be the jettisoned sun shade disintegrating in the atmosphere. It could also be the AO (propulsion) module, the PO module, or both (it is believed by analysts that the AO (propulsion) module is providing the retrofire boost necessary for the de-orbit of the OSA re-entry vehicle. It is believed that the OSA does not have its own retrofire rocket).

    Additional Kosmos 2495 parts surviving until re-entry over the USA at 4:30 UT, Sep 3

    How does this fit in with the observations over the USA 10 hours later?

    A clue is provided by previous Kobalt-M missions. At the end of five of these (Kosmos 2410, Kosmos 2420, Kosmos 2427, Kosmos 2445 and Kosmos 2462) pieces of debris were detected and catalogued by US tracking facilities that survived for several hours after the OSA re-entry vehicle touched down at Orenburg. In four of the five cases, it concerns two debris pieces (the fifth case, Kosmos 2462, produced three pieces). These debris pieces had the following SSC catalogue numbers and usually Cospar sub-designations C and D, or D and E:

    For Kosmos 2410: 28501 and 28502
    For Kosmos 2420: 29258 and 29259
    For Kosmos 2427: 32048 and 32049
    For Kosmos 2445: 33969 and 33970
    For Kosmos 2462: 36821, 36822 and 36823
     
    Of interest is that these debris pieces are only detected at the very end of the Kobalt-M mission, around the time of the OSA return vehicle re-entry at Orenburg. They hence seem to have to do with alterations to the satellite in preparation for the OSA separation and re-entry. As it happened on at least five of the missions, it seems a normal element of these missions. In fact it might have happened on all missions, but not all might have been detected: most of the objects above have only one or two element sets released indicating short detection spans. Their lifetimes typically are no more than a few hours to a day, so they can be missed.

    From the catalogued orbits of these debris pieces, there are suggestions that the separation of these objects from the original satellite body actually happens a few hours before the OSA re-entry. For Kosmos 2410, this is very clear as the debris pieces were first detected some 16 hours before the OSA re-entry, and while the A-object (presumably containing the OSA) was still being tracked.

    The likely re-entry seen from Wyoming, Colorado and New Mexico 10 hours after the OSA re-entry vehicle return over Orenburg, could very well concern similar debris pieces generated by Kosmos 2495. Analogues from another Kobalt-M mission suggests this is a realistic option.

    The Kosmos 2445 analogue

    Kosmos 2445 (2008-058A), another Kobalt-M mission from 2009, provides a very nice analogue. On its last day of existence it produced two debris pieces with catalogue numbers 33969 and 33970, that survived for several hours after the OSA re-entry. The OSA return occured on 23 Feb 2009 at 16:15 UT. We know this because this OSA re-entry was observed, as reported by Lissov. The last available tracking data for the two Kosmos 2445 debris pieces have an epoch near midnight of Feb 23-24, 2009, indicating survival for at least 8 hours after the Kosmos 2445 OSA return at Orenburg.

    I have used Alan Pickup's SatEvo software to further analyse the likely decay time for these debris pieces: the analysis suggests decay near 1:30-1:40 UT on 24 Feb, 2009. This is 9.5 hours after the OSA return.

    This 9.5 hours survival time of the Kosmos 2445 debris pieces is similar to the time difference between the Sep 2, 18:14 UT Kosmos 2495 OSA return observed from Kazakhstan, and the possible decay event observed over the USA at Sep 3, 4:30 UT. The time difference between these is about 10 hours, which is not much different from the ~9.5 hours for the Kosmos 2445 debris in 2009.

    During their last few orbits in February 2009, the Kosmos 2445 debris pieces C and D moved somewhat in front of where the A-object (the part including the OSA re-entry module) would have been had it not been de-orbitted. The difference in pass time was a few minutes.

    Relative position of Kosmos 2445 C and D debris pieces a few minutes in front of where the A-body would have been, just before decay early Feb 24, 2009 (movement is top to bottom)
    (click image to enlarge)

    This again provides a nice analogue to the September 2-3 event over the USA: the decaying object observed from the USA moved along the Kosmos 2495 A-object trajectory, but passing 2-3 minutes earlier than the predicted A-object passage (i.e., it was moving slightly in front of where the A-object would have been had it not been de-orbitted over Orenburg). Also note the slight westward displacement of the A object (red) trajectory.

    So: likely Kosmos 2495 debris re-entering over the USA after all!

    I feel that this all justifies to conclude that what was seen from the USA on the evening of September 2-3, indeed were parts of Kosmos 2495 re-entering. The close agreement of the observed fireball track with the predicted trajectory and predicted pass times for Kosmos 2495 is too good to be likely coincidence. The whole event moreover fits patterns of previous Kobalt-M missions, notably that of Kosmos 2445 in 2009: debris pieces surviving for a few hours after the OSA return vehicle re-entry, decaying ~ half a day later.

    So while it was not the return capsule with the camera and film that re-entered over the USA, it were nevertheless almost certainly parts of Kosmos 2495.

    Remember that denial (see another version here) by the Russian military? Read it carefully. What they actually deny is that Kosmos 2495 exploded, and they say "that nothing out of the ordinary happened".

    That is true. The return capsule separated successfully and presumably landed safely at Orenburg near 18:14 UT, as observed from Kazachstan. And Kosmos 2496 did not explode over the USA: debris parts left after the OSA separation decayed over the USA. Generation of such debris pieces seems to be normal for a Kobalt-M mission. So yes, "nothing out of the ordinary happened". It is all a clever word game.

    On the nature of those debris pieces

    What the nature of those debris pieces generated at the end of most (if not all) Kobalt-M missions and probably seen decaying over the US exactly is remains unclear. Behind the scenes, several independent analysts including me have had e-mail discussions about this the past 24 hours. Separation of the Kosmos into three modules (AO, PO and OSA), one of which (the OSA) makes a controlled re-entry over Orenburg for recovery, would make you think the remaining two debris pieces are these two other modules, the OA and PO. However, it is generally believed that the AO/PO combination provides the retrofire necessary for the OSA de-orbit and hence goes down with the OSA.  It is believed that the OSA module itself has no retrofire capacity (if it would have, it would separate from the other modules and then fire its own retrorocket, leaving the other two modules in orbit).

    So analysts have proposed that the debris pieces instead are satellite parts like solar panels (which are 6 meters in lenght each)  and antennae shed somewhat before the OSA re-entry. That idea is more likely yet in itself not entirely unproblematic either. In the case of Kosmos 2410 in 2005, the debris pieces were generated at least 16 hours (if not more) before the OSA reentry. It seems somewhat unlikely that you shed power sources (solar panels) and communication equipment (antennae) so many hours before the OSA re-entry.

    The observations from the USA on September 2-3 suggest a seizable object. This is not small debris, but definitely a large object.

    So that part of the story remains a bit of a mystery.


    UPDATE 1, 11 Sep 2014, 15:00 UT:

    Dr Bill Cooke of the Meteoroid Environments Office at NASA's Marshall Space Flight Center informed me (and this information is posted here with his kind permission) that their camera systems catched the event from New Mexico. From the data they determined that the object entered with a speed of  7.69 +/- 0.07 km/s.

    That is too slow for an object in heliocentric orbit (a meteor), but the typical speed of an object entering from Low Earth Orbit. Basically, this confirms that the event over the USA was the decay from orbit of (a part of) an artificial satellite.

    I thank Dr Cooke for communicating this vital piece of information.

    UPDATE 2, 15 Sep 2014, 15:30 UT: 

    Ted Molczan has published an excellent analysis into the area-to-mass ratio's of past Kobalt-M debris, which compares favourable to the area-to-mass ratio needed for Kosmos 2465 debris shed at OSA separation to decay over the US at 4:33 UT.

    Acknowledgement: I thank Ted Molczan, Jon Mikkel and Jonathan McDowell for the exchange of ideas. Igor Lissov provided valuable data on the Kazakhstan sightings and earlier sightings of Kobalt-M OSA re-entries from that region on Seesat.

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