Reentry predictions for the Chinese CZ-5B rocket stage 2021-035B [UPDATED]

UPDATE:

CSpOC/18th Space Control Squadron report that the CZ-5B rocket booster 2021-035B met a fiery end at 2:14 UT last night (May 9) over the Arabian peninsula and Indian Ocean. China reports reentry at 2:24 UT in the Indian Ocean near the Maldives

click map to enlarge

UPDATES 9 May 2021, 9:00 UT and 14:30 UT:

In the map above, I have plotted the approximate final trajectory (based on a SatEvo-evolved orbit propagated to reentry) and both the reentry locations reported by China (2:24 UT, 2.65 N, 72.64 E, in the Indian Ocean near the Maldives) and by CSpOC/18th Space Control Squadron (2:14 UT, 22.2 N 50 E, over the Arabian Peninsula).

Note how within minutes of the reentry, the rocket passed over the city of Riyahd in Saoudi-Arabia!

In looking at the plot, one should realize that a reentry is not an instantanious moment, but a process stretching over many minutes, where the object starts to break up and fragments burn up in the upper atmosphere. During this process, the object continues to move over a swat of trajectory that can be hundreds to a few thousands of kilometers long. It is very likely that this proces started over the Middle East or even over the Mediterranean already [edit: imagery from Jordan suggest that the object was still intact when passing over that location, but see a potential video from Oman below]. If fragments survived, they are scattered somewhere along the yellow line in the map, within the current uncertainties of the reentry location.

The video footage in the tweet below appears to show the (start of the) reentry, imaged from Oman, but is unverified for now:

وأخيرا سقط حطام #الصاروخ_الصيني

فيديو من سلطنة عمان يبين بداية دخوله للغلاف الجوي.

بحسب مصادر صينية، سقط الحطام في المحيط الهندي شمال المالديف.

بحسب مصادر أمريكية دخل الغلاف الجوي الساعة 02:14 أثناء مروره فوق سلطنة عمان وسقط الحطام أخيرا شمال المالديف. pic.twitter.com/aR6FEUHMd0

— مركز الفلك الدولي (@AstronomyCenter) May 9, 2021

I have tried, by fiddling with the area-to-mass ratio for the rocket in GMAT, to create a reentry trajectory that would match a splashdown in the Maldives around 2:24 UT, as reported by China. The closest I can get to the location reported by China is this result:

click map to enlarge

Of course, this is a simplified model (the proverbal "spherical cow in a vacuum") that does not take into account both mass loss from ablation and fragmentation over the reentry trajectory.

It however suggest that, if the time and location reported by China is right, the rocket stage would have been at an altitude of ~100 km around the position and time reported by CSpOC (the US military tracking network). It could be that the CSpOC position, with the quoted very small uncertainty in time of +- 1 minute, is based on a SBIRS satellite detection of the fireball (we have long suspected that TIP's with such 1-minute uncertainty quotes are based on satellite detections of the reentry fireball). 

About 100 km is a fair altitude for the ablative phase to start, similar to the altitude at which meteoric fireballs start. If the video from Oman above is the real deal, it is indeed suggested that ablation (and break-up) was starting over southern Arabia.

As a further update: interesting information about infrasound detections of the reentry from Djibouti, with source over the Arabian peninsula:

#CTBTO #IMS infrasound station IS19 #Djibouti🇩🇯 recorded an emergent, low-frequency signal of an object traveling at ~10000 km/h, compatible w/ re-entry of part of the #LongMarch5BRocket 🚀 over Arabian peninsula on 9 May @ 2:15 UTC & splash down in #IndianOcean near #Maldives pic.twitter.com/mlUlxtDI4b

— Lassina Zerbo (@SinaZerbo) May 9, 2021

[end of update]

(below is the  pre-reentry  version of this frequently updated post):

(this part below last updated 8 May 23:00 UT)

On 29 May  April, China used a CZ-5B rocket to launch the core module of it's new Space Station Tianhe-1 ("Harmony of Heavens-1"). The module was initially placed in a 41.5 degree inclined, 382 x 171 km orbit and subsequently raised to a 385 x 352 km orbit.

The massive CZ-5B core stage from the CZ-5B rocket used for this launch was left in a 375 x 170 km orbit. Like it's predecessor that flew in May 2020, it was not deorbited after payload release. This likely means that it will come down in an uncontrolled reentry somewhere on May 8 or 9.

Compared to 'normal' rocket upper stages (which are typically 3 to 10 meters long and say 1000-2500 kg in mass), the CZ-5B core stage is huge. It is 31 meters long, 5 meters in diameter, and very heavy: sources differ on the dry mass, but it is somewhere between 17 and 22 tons.

 

The informal Space industry standard for objects that are heavier than 10 tons, and launched into Low Earth Orbit, is to have a deliberate deorbit over an empty stretch of Ocean. This did not happen with the CZ-5B core stage from the 5 May 2020 launch a year ago, and does not seem to happen now following the Tianhe-1 launch either.

An uncontrolled reentry of an object this large and heavy means that sizable fragments can survive reentry and reach the surface of the earth, with the risk that this happens over inhabited parts of the world. This is not something that you want, from safety concerns. Several analysts have gone on the record calling the lack of a controlled reentry for the CZ-5B core stage 'irresponsible' for that reason.

I’ll just reiterate that uncontrolled re-entries of large rocket stages in 2021 is absolutely irresponsible behavior https://t.co/Q6RZAyFPpZ

— brianweeden (@brianweeden) April 30, 2021

Indeed, there are risks. For example, sizable fragments from the core stage of the previous CZ-5B launch, that also came down in an uncontrolled reentry, rained down on well populated parts of Ivory Coast in Africa in May 2020.

With the first lauch and uncontrolled reentry of a CZ-5B core stage a year ago, the question was whether a deliberate deorbit was planned but failed, or whether the CZ-5B core stage simply does not have a deorbit capability. As history now seems to repeat with this second CZ-5B launch, it starts to look like the CZ-5B indeed has no deorbit capability. This is highly surprising, and, indeed, irresponsible imho.

At the same time, while there is a risk (see what happened a year ago in Ivory Coast), the risk should not be overstressed. The risk that a random passenger aircraft ends up falling on your house is still orders of a magnitude larger, and we all have come to accept that risk.

We should also realize that much of the 17 to 22 tons mass of the stage will burn up before it reaches earth surface. Moreover, as a large part of the Earth consists of Ocean, it is likely that it will come down harmlessly over some Ocean.

Yet, it cannot be excluded that it will come down over a populated area, so some worry is justified. With an orbital inclination of 41.5 degrees, locations between 41.5 N and 41.5 S are in the danger zone for this reentry. The danger is slightly elevated at the extremes of this (41.5 N and 41.5 S). The latitude range where the CZ-5B booster can come down includes the whole of the United States, Australia, Africa, the southern parts of Asia and much of southern America. Europe is mostly safe, except for Spain, Italy and the Balkans:

 

When the reentry happens, the rocket stage will break up in the atmosphere and any surviving parts that have not burned up completely will rain down along the ground path along a very long stretch of earth: the area where fragments fall down can be hundreds of kilometers long.

 

PREDICTIONS

The diagram in the very top of this post gives reentry predictions. I will update it every time I run a new prediction. Below are the same predictions in table form. They are based on modelling of the orbital evolution in the General Mission Analysis Tool (GMAT).

Modelling is done for a mass of 17 tons (note that the true dry mass of the rocket stage is a bit uncertain: quoted values range between 17 and 22 tons, depending on the source) and with a drag surface at 60% of the maximum surface, as I have found that this generally fits well with tumbling rocket stages (which as a result of the tumbling have a variable drag surface). 

Each new prediction is based on a new orbital update from CSpOC. The MSISE90 model atmosphere is used, with past, current and estimated future Space Weather.

Note that these predicted reentry times are nominal values only. PLEASE NOTE THE VERY LARGE UNCERTAINTY IN THESE TIMES! 

The uncertainty margins shown are calculated as 20% of the time between the orbital epoch on which the prediction is based, and the predicted reentry time.

Note that the nominal position shown is only nominal: it is for the center of the uncertainty interval, but as long as the uncertainties in the reentry time measure in the hours, it is basically meaningless.

 

DATE      *NOMINAL* TIME        (issued)     (*nominal* position)

8 May     19:23 UT +- 22 hr     (May 4.22)

8 May     21:23 UT +- 21 hr     (May 4.46)

8 May     20:40 UT +- 21 hr     (May 4.53)

8 May     19:41 UT +- 20 hr     (May 4.59)

8 May     20:46 UT +- 18 hr     (May 5.08)

8 May     21:36 UT +- 18 hr     (May 5.20)

8 May     21:18 UT +- 16 hr     (May 5.51)

9 May     00:10 UT +- 16 hr     (May 5.58) 

9 May     04:40 UT +- 13 hr     (May 6.50)

9 May     03:52 UT +- 10 hr     (May 7.18)

9 May     04:01 UT +-  9 hr     (May 7.36)

9 May     03:36 UT +-  5 hr     (May 8.17)

9 May     03:10 UT +- 3.5 hr    (May 8.40)   (07 N 108 W)

9 May     03:11 UT +- 1.8 hr    (May 8.77)   (11 N 103 W)

9 May     02:54 UT +- 1.3 hr    (May 8.86)   (31 S 155 W) 
 

Uncertainties in the predicted reentry times will remain very large untill very shortly before the actual reentry.

click map to enlarge

Within the 2 hour wide uncertainty window of the current CSpOC TIP (9 May 2:04 UT +- 1 hr), which no doubt is more reliable than my amateurish efforts, the rocket stage can come down anywhere on the lines drawn in the map above (the lines show the rocket's trajectory over the uncertainty window). Within the risk window, the trajectory runs over central America, southern Europe, Arabia and the southern tips of Australia. China itself now appears to be out of the risk zone, ironically enough. The nominal point (but: with such a wide uncertainty that it is still basically meaningless!!!) is over Spain

The yellow dots in the map are those cities with populations of a million or more between 41.5 N and 41.5 S.

Other sources of predictions:

Most notably: Space-Track (the CSpOC portal: requires an account), which should be regarded as the most authoritive one.

Also: EU SST on Twitter

...and otherwise: Joseph Remis on Twitter, and Aerospace Corporation 

(note how all of these give somewhat differing forecasts: which shows you how difficult these reentry forecasts are!)

Several years ago I wrote a FAQ about reentries, and reentry predictions, that might answer any questions you have.

I will update this post with new data when I have the opportunity.

Chinese CZ-11 rocket stage impacts Myanmar Jade quarry (updated)

On November 9 at 23:42 UT (November 10 in local time), China launched a Long March 11 (CZ-11) rocket from Jiuquan on a south-bound trajectory, lofting the XPNAV satellite into orbit.

The object (image from the Myanmar Times)

Shortly after this, an object came crashing out of the sky in Myanmar, impacting in a Jade quarry near Hmaw His Zar village near Hpakant in Kachin Province. Photographs of the object can be seen in the news stories here and  here. The image in the first link is the best in terms of showing shape and size.

The object is reportedly ~4 meter long and ~1.5 meter wide (reports differ slightly). In one of the images, it is clear that it is different in diameter at both ends, the shape being that of a barrel with a tapering segment on it.

Size and shape conforms to (what I assume is) the second stage of the CZ-11 (edit: might in fact be the 3rd stage), which is about ~4 meters long and about 2 meter diameter at one side, tapering to about 1.4 meter diameter at the other side. A drawing of the rocket's elements is here and another, perhaps more accurate rendering is here (the drawings differ somewhat, hence my confusion on whether this is the 2nd or 3rd stage. From the second rendering, it looks to be the 3rd rather than the 2nd stage).

Click map to enlarge

As can be seen in the map above, last Wednesday's Chinese launch trajectory lines up well with the reported location of the impact in Myanmar.  So it almost certainly is the 2nd (3rd?) stage of the CZ-11 rocket used for this launch.

[edit 12 Nov 2016: to be clear, the line on the map is a projection of the orbital plane of the XPNAV satellite at the moment of launch, as a proxy for the launch trajectory. You can see it lines up with both the Jiuquan launch location and the location where the object came down in Myanmar].


UPDATE: Jeffrey Lewis ("The Arms Control Wonk") pointed me to this Chinese CNTV footage about the recent launch that shows various parts of the CZ-11 rocket. From 0:35 onwards, one of the stages shown visually clearly is a match for the Myanmar objects:



Here are a few stills from the footage, compared to one of the images of the Myanmar object. The red semi-transparent boxes indicate which stage matches in terms of shape and details such as the round hole halfway the hull:

click to enlarge

(editted 12 Nov: added images and text, noted the 2nd/3rd stage potential confusion)

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:

        Zc =  r - 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 19.3^o E and below 46.45^o N, and happened some time after 03:39:20 UT. It likely not survived much beyond longitude 21^o 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 47^o N longitude 17^o 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. 

Brightness variability of the NOSS 3-3 Centaur Upper Stage (with video)

NOSS 3-3 is a pair of US Navy NOSS surveillance satellites launched early 2005. The Centaur upper stage of this NOSS 3-3 launch, NOSS 3-3r (2005-004B) is still orbiting earth as well. And as it does so, it is tumbling.

This tumbling is visible to an observer as a regular variation in brightness. Currently, the rocket stage brightens up every 11.4 seconds.

Below video shows the regular variation in brightness: watch it go from faint to bright to faint etcetera with an 11.4 second period. It is footage from a pass over Leiden which I filmed in the evening of March 22, using the WATEC 902H and a Canon EF 2.0/35 mm lens:

click images to enlarge

Using LiMovie, I extracted the brightness variation from the movie on a frame by frame basis, resulting in the depicted brightness profile above. Note that the tops of the curve are sharp, not rounded. It is a nice saw-tooth pattern. The integrated video frame picture shows the brightness variability nicely too.

Documenting this kind of tumbling behaviour (and notably how it changes over the years) can actually provide some valuable scientific data. A number of amateur observers specialize in these "flash observations", notably my fellow members of the Belgian Working Group Satellites (BWGS).

Space debris lands in Brazil village

Through Carlos Bella on the satobs mailing list, news broke today that an object which almost certainly is space-debris crashed in the Brazilian village of Anapurus on February 22, 2012, near 6 am local time (9 UTC). It landed about 6 yards from a house and damaged trees upon impact.

Photo's of the object can be see here.They show a spherical object that strongly resembles a spherical rocket fuel cell (tank) or a Helium pressurization tank. These are the most resistent objects among space debris and often involved in reported cases of space-debris reaching earth surface.

Ted Molczan quickly noted that date, time and location correspond well to the re-entry of 1997-016C, an Ariane 44L rocket stage from the launch of two geostationary satellites, Thaicom 3 and Bsat-1A, on 17 April 1997.

The Ariane 44L r/b in question re-entered at 9:09 UTC +/- 1 min on 22 February 2012, near 4 S, 312 E. This corresponds well with the time and location of the Anapurus event (3.7 S, 317 E). Anapurus is located right on the re-entry track and was passed within a minute of the estimated re-entry time (movement of the r/b was from West to East, i.e. to the right in the map):

click map to enlarge