We are in for an interesting weekend, as the failed Russian Mars probe Phobos-Grunt is experiencing it's last days of existence. Gradually having come down over the past two months, it is expected to re-enter and burn up (but perhaps not completely) in the Earth atmosphere on Sunday or Monday.
Several days before the re-entry date, it is still not possible (whatever some news outlets erroneously write) to pinpoint when and where it will come down. At the moment of writing (early Friday), the SSC prediction amounts to a still over a day wide window between 15 Jan 02:40 and 16 jan 07:40 UTC. Harro Zimmer's latest prediction is for Jan 15 between 9:00 - 15:00 UTC. Both predictions encompass multiple revolutions around the earth. Please note: all these time windows can still shift, depending on actual developments in space weather (solar activity) and other factors.
Below video has been posted here before, and shows a Fobos-Grunt pass filmed by me from Leiden, the Netherlands, on November 28:
Showing posts with label re-entry. Show all posts
Showing posts with label re-entry. Show all posts
Friday, 13 January 2012
Tuesday, 27 December 2011
Further confusion on Saturday's Soyuz r/b reentry
I earlier wrote about the confusion reigning in the press concerning the sky event over Europe of last Saturday evening. Initial confusion was over wether it was a meteor, "comet" or (and that was the correct explanation, but many Dutch and German news outlets failed to properly pick that up): the reentry of a Soyuz rocket.
Now a new confusion has arrisen: some news outlets and weblogs, e.g. that of Physorg, mistakenly link the event to last Friday's failed Russian launch of the Meridian satellite. Due to a rocket failure, this never reached earth orbit but crashed in Siberia within minutes after the launch.
As I wrote earlier, what reentered and was seen over France, Germany and the Netherlands last Saturday evening, was the 3rd stage of last Wednesday's Soyuz launch to the ISS.
The confusion probably comes from the fact that both launches used a Soyuz rocket. The failed launch that crashed in Siberia on Friday got some press attention because fragments hit a house in Russia (see a.o. here (English), with pictures of a recovered fuel tank here (Russian)).
But again: that failed launch had nothing to do with Saturdays sky event over Europe. The reentry over Europe was the 3rd stage of the earlier Wednesday launch to the ISS, that included Dutch astronaut Andre Kuipers.
Now a new confusion has arrisen: some news outlets and weblogs, e.g. that of Physorg, mistakenly link the event to last Friday's failed Russian launch of the Meridian satellite. Due to a rocket failure, this never reached earth orbit but crashed in Siberia within minutes after the launch.
As I wrote earlier, what reentered and was seen over France, Germany and the Netherlands last Saturday evening, was the 3rd stage of last Wednesday's Soyuz launch to the ISS.
The confusion probably comes from the fact that both launches used a Soyuz rocket. The failed launch that crashed in Siberia on Friday got some press attention because fragments hit a house in Russia (see a.o. here (English), with pictures of a recovered fuel tank here (Russian)).
But again: that failed launch had nothing to do with Saturdays sky event over Europe. The reentry over Europe was the 3rd stage of the earlier Wednesday launch to the ISS, that included Dutch astronaut Andre Kuipers.
Monday, 26 December 2011
11-078B Soyuz 3rd stage reentry: answers to some frequently asked questions
In the wake of the spectacular reentry over NW Europe of the Soyuz 3rd stage 2011-078B on Saturday 24 December 2011, several common questions popped up in comments, e-mails, on Twitter and in newspaper discussions. I will answer a few below.
Frequently Asked Questions:
(Q1): Are these things predictable and who makes such predictions?
(Q2) Does it really take a Soyuz rocket 3rd stage three days to fall back to earth?
(Q3) Why doesn't this happen with each Soyuz launch? Or: why not over the same location on Earth?
(Q4) has anything of the rocket stage survived to earth surface?
Answers:
(Q1): Are these things predictable and who makes such predictions?
(A): It is "sort of" predictable. Using computer models which take into account many factors of influence, one can make a prediction yielding an indication of the time a rocket stage or satellite will re-enter the atmosphere. However, even very close to that actual time of reentry, the uncertainty in these predictions is still very large. Exactly when a rocket stage will start to burn up depends on many factors, including the exact condition of the atmosphere at that moment, the shape of the rocket stage, and whether it is tumbling or not. In practise, this turns out to be very difficult to model, even with the best computer models.
Several organisations and individuals do such predictions (and you can even find software for it on the internet). However, one of the most authoritive sources of such predictions is USSTRATCOM, the American military organisation that tracks manmade objects in space (many people think NASA does that job. But that is incorrect: it is USSTRATCOM, better known as 'NORAD'). They publish these predictions as 'TIP' messages. Their first prediction is published 2 months in advance. These still have a very large uncertainty (think of: weeks). In the days close to decay, they publish new estimates as new TIP messages that gradually become more exact. But even these can have uncertainties of several hours, even for predictions made on the day of the reentry itself.
For example, the last pre-reentry TIP message issued only 2 hours before the Soyuz 3rd stage came down, still had an uncertainty window of six hours.....
Once an object has reentered, USSTRATCOM does a post-analysis of the last orbital information, and publishes a "final' TIP message mentioning when and where the object came down (so this is done "after the fact"). These can be (but are not always, as it depends on how well the object was tracked during it's last hours of existence) very accurate. Sometimes, as was the case with this reentry of the Soyuz 3rd stage, they provide a time with an uncertainty of only minutes, plus a quite accurate position. In other cases, where less recent tracking data is available, the final uncertainty is much larger.
Note that a re-entering satellite or rocket booster has a speed of 7.5 km per second (4.7 miles per second)! So even if the predicted time has an uncertainty of just 15 minutes, this amounts to an uncertainty of 13,500 km (8,400 miles) in the position of the object when it reenters! This is why it is impossible to pinpoint the expected point of re-entry beforehand, when it is not a "controlled" re-entry. (in a "controlled" re-entry, the satellite operators send a command to the satellite to make a rocket burn at a precise time, kicking it down over a designated spot, usually the Pacific ocean. This Soyuz reentry was however not such a "controlled" reentry).
Many people mistakenly think that in this day and age of supercomputers, scientists (or the military) can predict everything. In reality, satellite/rocket reentries like this are so complex that even the best computer models can only give rough indications untill just minutes before the actual re-entry.
(Q2) Does it really take a Soyuz rocket 3rd stage three days to fall back to earth?
(A) Yes, it does. That last rocket stage is jettisoned that high above earth surface, that it does not just rapidly fall back on a ballistic trajectory (such as the 1st and 2nd stages do) but actually reaches Low Earth Orbit, and stays in orbit around the earth for several days. In effect, it becomes a satellite for a while in a very low orbit around Earth. Under influence of gravity and drag from the outer atmosphere, the orbit slowly evolves and becomes smaller and smaller. On the first day only gradually, but as it slowly comes down, this gradually goes faster and faster.
The influence of our atmosphere reaches several hundreds of kilometers up: even the International Space Station experiences some atmospheric drag, and would fall down within a year if its orbit was not regurlarly raised using the rocket engines of the Progress spacecraft docked to the ISS.
It takes about 3-4 days for a Soyuz 3rd stage from a launch to the ISS to come down. The exact amount of time is variable and different in each new case, as it depends on many factors. Our atmosphere is variable in extent and density, notably under the influence of solar activity. When the sun is active and many charged particles from solar outbursts reach earth, these interact with our atmosphere and the atmosphere slightly expands as a result of this. This means that objects at the altitude of the Space Station and below that (such as the Soyuz rocket stage) will experience a "thicker atmosphere", i.e. more drag from the atmosphere's outermost layers, and as a result they will come down faster. When it reaches at altitude of only 120 km (75 miles) it goes very quick: within minutes the rocket stage has dropped tens of kilometers, slowed down considerably, and finaly plunges straight down from that moment onwards.
The exact moment this happens, is highly dependant on these variations in extend of our atmosphere due to variations in solar activity. This is another reason why a satellite or rocket re-entry is so difficult to predict: one short but intense outburst occuring on the sun will next make a rocket stage fall back much quicker than expected.
Below diagram shows the orbital evolution of the Soyuz 3rd rocket stage that decayed last Saturday. It had to make 52 full orbits (full circles) around the Earth before it burned up. It's orbit was a bit "eccentric", which means that it was not a perfect circle but an ellipse. So on each revolution around the earth, there is a point where it is a bit higher above earth (called the "apogee") and a point where it is closest to the earth (called "perigee"). In the diagram, the values for these altitudes have been plotted as a red and blue line. Note how fast these altitudes change in the final hours before re-entry.
(Q3) Why doesn't this happen with each Soyuz launch? Or: why not over the same location on Earth?
(A) It does happen with each Soyuz launch to the ISS. The Soyuz 3rd stage always comes down some 3-4 days after the launch.
That reentry however is never over the same location on earth. The reasons for this, have already been outlined as part of the answer to question (2) above. An important factor of influence on how quickly a rocket stage comes down, is the variable earth's atmosphere, under influence of variability in solar activity. These factors are different for each new case. This is why the 3rd stages of Soyuz launches to the ISS never fall down near the same spot twice.
(Q4) has anything of the rocket stage survived to earth surface?
(A) Not that we so far know of. Usually, the rocket stage almost completely burns up in the atmosphere. Sometimes, a few smaller bits survive (quite often spherical fuel tanks). For example, an object that is likely a rocket fuel tank came down in Namibia in November and might be part of a rocket stage used in a Russian November launch to the International Space Station.
Frequently Asked Questions:
(Q1): Are these things predictable and who makes such predictions?
(Q2) Does it really take a Soyuz rocket 3rd stage three days to fall back to earth?
(Q3) Why doesn't this happen with each Soyuz launch? Or: why not over the same location on Earth?
(Q4) has anything of the rocket stage survived to earth surface?
Answers:
(Q1): Are these things predictable and who makes such predictions?
(A): It is "sort of" predictable. Using computer models which take into account many factors of influence, one can make a prediction yielding an indication of the time a rocket stage or satellite will re-enter the atmosphere. However, even very close to that actual time of reentry, the uncertainty in these predictions is still very large. Exactly when a rocket stage will start to burn up depends on many factors, including the exact condition of the atmosphere at that moment, the shape of the rocket stage, and whether it is tumbling or not. In practise, this turns out to be very difficult to model, even with the best computer models.
Several organisations and individuals do such predictions (and you can even find software for it on the internet). However, one of the most authoritive sources of such predictions is USSTRATCOM, the American military organisation that tracks manmade objects in space (many people think NASA does that job. But that is incorrect: it is USSTRATCOM, better known as 'NORAD'). They publish these predictions as 'TIP' messages. Their first prediction is published 2 months in advance. These still have a very large uncertainty (think of: weeks). In the days close to decay, they publish new estimates as new TIP messages that gradually become more exact. But even these can have uncertainties of several hours, even for predictions made on the day of the reentry itself.
For example, the last pre-reentry TIP message issued only 2 hours before the Soyuz 3rd stage came down, still had an uncertainty window of six hours.....
Once an object has reentered, USSTRATCOM does a post-analysis of the last orbital information, and publishes a "final' TIP message mentioning when and where the object came down (so this is done "after the fact"). These can be (but are not always, as it depends on how well the object was tracked during it's last hours of existence) very accurate. Sometimes, as was the case with this reentry of the Soyuz 3rd stage, they provide a time with an uncertainty of only minutes, plus a quite accurate position. In other cases, where less recent tracking data is available, the final uncertainty is much larger.
Note that a re-entering satellite or rocket booster has a speed of 7.5 km per second (4.7 miles per second)! So even if the predicted time has an uncertainty of just 15 minutes, this amounts to an uncertainty of 13,500 km (8,400 miles) in the position of the object when it reenters! This is why it is impossible to pinpoint the expected point of re-entry beforehand, when it is not a "controlled" re-entry. (in a "controlled" re-entry, the satellite operators send a command to the satellite to make a rocket burn at a precise time, kicking it down over a designated spot, usually the Pacific ocean. This Soyuz reentry was however not such a "controlled" reentry).
Many people mistakenly think that in this day and age of supercomputers, scientists (or the military) can predict everything. In reality, satellite/rocket reentries like this are so complex that even the best computer models can only give rough indications untill just minutes before the actual re-entry.
(Q2) Does it really take a Soyuz rocket 3rd stage three days to fall back to earth?
(A) Yes, it does. That last rocket stage is jettisoned that high above earth surface, that it does not just rapidly fall back on a ballistic trajectory (such as the 1st and 2nd stages do) but actually reaches Low Earth Orbit, and stays in orbit around the earth for several days. In effect, it becomes a satellite for a while in a very low orbit around Earth. Under influence of gravity and drag from the outer atmosphere, the orbit slowly evolves and becomes smaller and smaller. On the first day only gradually, but as it slowly comes down, this gradually goes faster and faster.
The influence of our atmosphere reaches several hundreds of kilometers up: even the International Space Station experiences some atmospheric drag, and would fall down within a year if its orbit was not regurlarly raised using the rocket engines of the Progress spacecraft docked to the ISS.
It takes about 3-4 days for a Soyuz 3rd stage from a launch to the ISS to come down. The exact amount of time is variable and different in each new case, as it depends on many factors. Our atmosphere is variable in extent and density, notably under the influence of solar activity. When the sun is active and many charged particles from solar outbursts reach earth, these interact with our atmosphere and the atmosphere slightly expands as a result of this. This means that objects at the altitude of the Space Station and below that (such as the Soyuz rocket stage) will experience a "thicker atmosphere", i.e. more drag from the atmosphere's outermost layers, and as a result they will come down faster. When it reaches at altitude of only 120 km (75 miles) it goes very quick: within minutes the rocket stage has dropped tens of kilometers, slowed down considerably, and finaly plunges straight down from that moment onwards.
The exact moment this happens, is highly dependant on these variations in extend of our atmosphere due to variations in solar activity. This is another reason why a satellite or rocket re-entry is so difficult to predict: one short but intense outburst occuring on the sun will next make a rocket stage fall back much quicker than expected.
Below diagram shows the orbital evolution of the Soyuz 3rd rocket stage that decayed last Saturday. It had to make 52 full orbits (full circles) around the Earth before it burned up. It's orbit was a bit "eccentric", which means that it was not a perfect circle but an ellipse. So on each revolution around the earth, there is a point where it is a bit higher above earth (called the "apogee") and a point where it is closest to the earth (called "perigee"). In the diagram, the values for these altitudes have been plotted as a red and blue line. Note how fast these altitudes change in the final hours before re-entry.
(Q3) Why doesn't this happen with each Soyuz launch? Or: why not over the same location on Earth?
(A) It does happen with each Soyuz launch to the ISS. The Soyuz 3rd stage always comes down some 3-4 days after the launch.
That reentry however is never over the same location on earth. The reasons for this, have already been outlined as part of the answer to question (2) above. An important factor of influence on how quickly a rocket stage comes down, is the variable earth's atmosphere, under influence of variability in solar activity. These factors are different for each new case. This is why the 3rd stages of Soyuz launches to the ISS never fall down near the same spot twice.
(Q4) has anything of the rocket stage survived to earth surface?
(A) Not that we so far know of. Usually, the rocket stage almost completely burns up in the atmosphere. Sometimes, a few smaller bits survive (quite often spherical fuel tanks). For example, an object that is likely a rocket fuel tank came down in Namibia in November and might be part of a rocket stage used in a Russian November launch to the International Space Station.
Saturday, 24 December 2011
[Updated] Breaking News: Decay of Soyuz r/b stage from André Kuipers' launch to ISS observed from the Netherlands!
UPDATE - the final TIP for Soyuz r/b 38037 / 2011-078B has been released by USSTRATCOM near 18h GMT and it indeed shows that this was the Soyuz r/b: reentry time is quoted as 16:25 +/- 1 minute GMT at 49 deg N, 7 deg E. This fits the observations well.
In the Dutch press, there meanwhile appears to be a lot of confusion. The Dutch National Police claims that they talked to "NASA" who apparently said it was a "meteor" (or "comet"). So THAT is widely claimed in the press now, to the point of calling the identification with the Soyuz 3rd stage "speculation". Which it is not: it is based on factual data and now clearly confirmed by the USSTRATCOM JSpOC TIP message. What more do you want?!
I have no idea to whom (or even where: NASA is big...) the Police spoke, but for all things it could have been the JPL janitor....
At any rate: appart from my analysis below (which is already clear), the USSTRATCOM TIP message mentioned above makes unambiguously clear that this was the Soyuz 3rd stage.
Note that to access the USSTRATCOM TIP message via the link above you need an approved account. USSTRATCOM is the US military Command responsible for tracking manmade objects in space, and perhaps better known under their former name NORAD.
- end of update
Multiple reports are coming in, among others by experienced Dutch meteor observers Carl Johannink (Gronau) and Arnold Tukkers (Denekamp), of a bright and very slow fragmenting object seen low in the west-southwest near Venus at 16:26 UTC, 24 December.
From the descriptions it clearly was a reentry of an artificial object (space junk), as the event was too long in duration and too slow to be a meteoric fireball.
And it was not "just" a random bit of space debris, it turns out:
The observations fit with 2011-078B (#38037), the last stage of the Soyuz rocket that brought Dutch astronaut Andre Kuipers up to the ISS earlier this week. It was already predicted to decay near this moment by USSTRATCOM.
Below is the predicted trajectory of the Soyuz 3rd stage for the Gronau/Enschede area (and below that, the ground trajectory). It is based on an orbit with an epoch near noon of 24 December (epoch 11358.49032868. Source: USSTRATCOM), so a few hours old, which will introduce some minor discrepancies (a few seconds in time). But it fits the descriptions very well in terms of time and trajectory in the sky.
click images to enlarge
[UPDATE 7 October 2017]:
I recently modelled the re-entry of 2011-078B in GMAT, using the MSISE90 model atmosphere with actual Spaceweather of that time. Drag surface was set at 60% of the maximum drag surface for a Soyuz upper stage: this yields a decay position and decay time well in agreement with the JSpOC TIP position and is close to what the drag value for a tumbling, fragmenting object would be.
As seen from Gronau in Germany, it yields the following sky trajectory. Compare with Carl Johannink's description below: it matches his description well.
 |
| click map to enlarge |
- continuing original post:
Some quickly translated descriptions by two experienced Dutch meteor observers (compare to the sky trajectory map above for their area):
Arnold Tukkers, Denekamp (Netherlands):
At 17:26 CET (=16:26 UTC) I looked out of the window and saw a strange phenomena just above the rooftops behind us. It looked like a very, very slow meteor fragmented in several pieces. Like Peekskill but less bright.
Multiple fragments. Because it was so low in the sky, I walked upstairs and could still see the last part from the bedroom window. So it at least took 20 seconds. [...]
What a sight! Trajectory for me (did not see initial part) southwest-southeast. Altitude maximum 20 degrees. Colour brown-red.
Carl Johannink, Gronau (Germany):Update:
Just was looking at Venus in evening twilight.
Left of it an object appeared from behind a cloud that I first thought to be an aircraft, but next I found something was not right. The thing sometimes brightened and became fuzzy, trailing a circa 8 degree long tail. Maximum brightness about -4.
The object roughly moved from SSW to SE at an elevation of about 15 degrees. The whole phenomena took over half a minute.
To see the second part of the trajectory I had to walk to a different room. Called in Elisabeth, together we saw the object fragment into pieces (each individual piece about mag. 0 to +1) and then fade out.
The whole event looked much alike to the New Years Eve satellite decay of 1978, albeit being somewhat less bright.
A number of video's from Germany have surfaced which likely show the event. Here are a few:
video 1
video 2
Video 3 (on the Bad Astronomer's blog)
Video 4
Video 5
FAQ
Read the answers to Frequently Asked Questions for this reentry case I published later here.
Friday, 11 November 2011
If rescue fails, Fobos-Grunt will reenter soon
As new attempts to contact the probe failed, the future is looking increasingly grim for Fobos-Grunt (aka "Phobos-Grunt" and "Phobos-SOIL"), the Russian space probe launched on 8 November that should have gone to the Martian moon Phobos for a sample return mission, but instead got stuck in Low Earth Orbit.
The probe is currently stuck in a very low orbit measuring 207 x 339 kilometer after it's propulsion unit apparently failed, failing to lift it into a GTO (and from there an interplanetary trajectory):
If the probe isn't revived in due time - and the Russsian operators are still frantically trying to do so - it is doomed. With an orbit at this low an altitude, it is a short matter of time before it comes down again - another case of an imminent uncontrolled reentry of a very large satellite (over 13 metric tons, including the fuel). How much fuel is onboard is not clear to me: different media sources quote quite different amounts, but all amounts quoted are in terms of several tons, with several sources settling for 7 tons (see also here).
As pointed out here by Anatoly Zak, seizable chunks of the probe could survive reentry, and survival is certainly expected for the actual Fobos sample return capsule (which was designed for reentry).
Reentry estimates
Estimates of when Fobos-Grunt will come down are a bit complicated. Ted Molczan has noted that over the past day, the orbital evolution was unusual - Ted points out that if the last two orbit releases are not faulty (a possibility), it means that either the probe is manoeuvering (which from all the negative statements by the Russians in the press seems unlikely) or - more likely - has started to vent fuel since yesterday. As a result, it might have gotten a very mild orbital boost (the leaking fuel acts like a small rocket engine).
Before this unusual behaviour started, orbital elements 11314.14749491 to 11314.77184893 and Alan Pickup's SatEvo software with current solar activity levels suggested a nominal reentry time no later than early January 2012. SSC meanwhile predicts reentry for November 26th, 2011. The current unusual orbital evolution - if real - might change things a bit, but eventually it will come down.
This means it will likely come down somewhere over the next few weeks or months if the operators cannot revive it over the next two weeks. With an orbital inclination of 51.4 degrees, it can come down anywhere between 51 N and 51 S latitude.
There has been a call out to observers to observe the probe - it's brightness behaviour can yield clues as to whether it is starting to tumble, e.g. because of the suspected fuel venting. So far, observations by Brad Young and Michael Murphy from the US suggest the probe is stable in brightness with no sign of tumbling (see here and here).
Unfortunately, the probe is currently not visible from NW Europe where I am located: it makes passes near midnight, completely in shadow.
The probe is currently stuck in a very low orbit measuring 207 x 339 kilometer after it's propulsion unit apparently failed, failing to lift it into a GTO (and from there an interplanetary trajectory):
If the probe isn't revived in due time - and the Russsian operators are still frantically trying to do so - it is doomed. With an orbit at this low an altitude, it is a short matter of time before it comes down again - another case of an imminent uncontrolled reentry of a very large satellite (over 13 metric tons, including the fuel). How much fuel is onboard is not clear to me: different media sources quote quite different amounts, but all amounts quoted are in terms of several tons, with several sources settling for 7 tons (see also here).
As pointed out here by Anatoly Zak, seizable chunks of the probe could survive reentry, and survival is certainly expected for the actual Fobos sample return capsule (which was designed for reentry).
Reentry estimates
Estimates of when Fobos-Grunt will come down are a bit complicated. Ted Molczan has noted that over the past day, the orbital evolution was unusual - Ted points out that if the last two orbit releases are not faulty (a possibility), it means that either the probe is manoeuvering (which from all the negative statements by the Russians in the press seems unlikely) or - more likely - has started to vent fuel since yesterday. As a result, it might have gotten a very mild orbital boost (the leaking fuel acts like a small rocket engine).
Before this unusual behaviour started, orbital elements 11314.14749491 to 11314.77184893 and Alan Pickup's SatEvo software with current solar activity levels suggested a nominal reentry time no later than early January 2012. SSC meanwhile predicts reentry for November 26th, 2011. The current unusual orbital evolution - if real - might change things a bit, but eventually it will come down.
This means it will likely come down somewhere over the next few weeks or months if the operators cannot revive it over the next two weeks. With an orbital inclination of 51.4 degrees, it can come down anywhere between 51 N and 51 S latitude.
There has been a call out to observers to observe the probe - it's brightness behaviour can yield clues as to whether it is starting to tumble, e.g. because of the suspected fuel venting. So far, observations by Brad Young and Michael Murphy from the US suggest the probe is stable in brightness with no sign of tumbling (see here and here).
Unfortunately, the probe is currently not visible from NW Europe where I am located: it makes passes near midnight, completely in shadow.
Sunday, 23 October 2011
ROSAT down over the Indian Ocean [RENEWED UPDATE]
ROSAT is no more.....according to a TIP bulletin by SSC issued at 03:41 UTC, it reentered at 1:50 UTC +/- 7 minutes, placing it over the Indian Ocean (and far away from any eyewitnesses, bar maybe some ships and maybe Ceylon, Sumatra and Birma/Malaysia/S-China if it survived into the second half of the given window: and of course the US tracking facility at Diego Garcia).
See update 2 below for latest map version (update 1 below now deprecated)
update 1 - deprecated.
[Below two map shows the final orbit and (thick red line) the reentry windows according two assessments:
- The first is with the last available TLE (issued over a day before the reentry) propagated with SatEvo.
- The second, is made by adjusting the time (by about 5 minutes) so that the satellite position matches the nominal position for the reentry given by SSC in the TIP bulletin: 7 N, 90 E]
[As can be seen there is some difference between these two. This is the result of there currently being no recent TLE available: the last available TLE dates 24 hours before the reentry. In the 24 hours between that last issued TLE and reentry, the orbit evolved fast. Without the availability of more recent elements, it is difficult to assess where the satellite exactly was along its orbit. That uncertainty is no more than a few minutes in time, but that amounts to over 2000 km in position....]
UPDATE 2: SSC released a new tle, with an epoch dating to two hours before the decay (about 1.5 revolutions). This allows this map to be created, which closely tallies with map 2 above:
It shows the difference a new TLE much closer in time to the decay makes, with regard to locating the satellite in its final moments....
(note: thanks to Daniel Fischer for inquiring about the differences between my map and Simone Corbellini's map, and to Simone for communications on the why of the time offset)
See update 2 below for latest map version (update 1 below now deprecated)
update 1 - deprecated.
[Below two map shows the final orbit and (thick red line) the reentry windows according two assessments:
- The first is with the last available TLE (issued over a day before the reentry) propagated with SatEvo.
- The second, is made by adjusting the time (by about 5 minutes) so that the satellite position matches the nominal position for the reentry given by SSC in the TIP bulletin: 7 N, 90 E]
click maps to enlarge
[As can be seen there is some difference between these two. This is the result of there currently being no recent TLE available: the last available TLE dates 24 hours before the reentry. In the 24 hours between that last issued TLE and reentry, the orbit evolved fast. Without the availability of more recent elements, it is difficult to assess where the satellite exactly was along its orbit. That uncertainty is no more than a few minutes in time, but that amounts to over 2000 km in position....]
UPDATE 2: SSC released a new tle, with an epoch dating to two hours before the decay (about 1.5 revolutions). This allows this map to be created, which closely tallies with map 2 above:
click map to enlarge
It shows the difference a new TLE much closer in time to the decay makes, with regard to locating the satellite in its final moments....
(note: thanks to Daniel Fischer for inquiring about the differences between my map and Simone Corbellini's map, and to Simone for communications on the why of the time offset)
Saturday, 22 October 2011
ROSAT reentry update (2)
Update to my previous post: Space-Track (SSC) finally released a new elset, 11294.85810509, which is still and "old" elset (almost a day old). And they released a new TIP with a new reentry prediction.
The new TIP gives this prediction:
Space-Track (SSC): 23 Oct, 02:34 UTC +/- 7 hrs
Based on the new TLE, independant analyst Harro Zimmer now provides the following prediction:
Harro Zimmer: 23 Oct, 04:17 UTC +/- 4 hrs
Other independant analysts have not updated yet (see my previous post for these values). I did a run of SatEvo with the newly released TLE and the current F10.7 cm solar flux, and get, for what it's worth, a projected time of 10:20 UTC (23 Oct) +/- 5 hrs. That seems a bit late compared to the SSC and Zimmer estimates (although the uncertainty windows of course overlap).
The new TIP gives this prediction:
Space-Track (SSC): 23 Oct, 02:34 UTC +/- 7 hrs
Based on the new TLE, independant analyst Harro Zimmer now provides the following prediction:
Harro Zimmer: 23 Oct, 04:17 UTC +/- 4 hrs
Other independant analysts have not updated yet (see my previous post for these values). I did a run of SatEvo with the newly released TLE and the current F10.7 cm solar flux, and get, for what it's worth, a projected time of 10:20 UTC (23 Oct) +/- 5 hrs. That seems a bit late compared to the SSC and Zimmer estimates (although the uncertainty windows of course overlap).
ROSAT reentry update
New independent updates on the projected moment of the ROSAT reentry are hampered by the fact that no new orbital elements have been released for 1.5 days now - the last elset released being elset 11294.06213865 (epoch time 21 Oct 01:29:29 UTC) as of this moment (22 Oct 12:10 UTC).
Meanwhile, here is a summary of the latest available predictions at this moment of writing:
Space-Track (SSC): 23 Oct, 01:31 UTC +/- 14 hrs
Aerospace Corp: 23 Oct, 13:24 UTC +/- 16 hrs
Harro Zimmer: 23 Oct, 05:33 UTC +/- 6 hrs
Ted Molczan (using SatEvo): 23 Oct, 05:00 +/- 10 hrs
T.S. Kelso: 23 Oct, 03:15 UTC (uncertainty not listed)
DLR: 23 Oct, ~3h UTC +/- 9hrs (midtime from window given)
The FAA has realeased a NOTAM warning for the reentry:
Meanwhile, here is a summary of the latest available predictions at this moment of writing:
Space-Track (SSC): 23 Oct, 01:31 UTC +/- 14 hrs
Aerospace Corp: 23 Oct, 13:24 UTC +/- 16 hrs
Harro Zimmer: 23 Oct, 05:33 UTC +/- 6 hrs
Ted Molczan (using SatEvo): 23 Oct, 05:00 +/- 10 hrs
T.S. Kelso: 23 Oct, 03:15 UTC (uncertainty not listed)
DLR: 23 Oct, ~3h UTC +/- 9hrs (midtime from window given)
The FAA has realeased a NOTAM warning for the reentry:
!FDC 1/9172 FDC SPECIAL NOTICE .. ..........EFFECTIVE IMMEDIATELY UNTIL 1110252359 UTC. AIRCRAFT ARE ADVISED THAT A POTENTIAL HAZARD MAY OCCUR DUE TO REENTRY OF THE SATELLITE ROSAT INTO THE EARTH'S ATMOSPHERE. THE FEDERAL AVIATION ADMINISTRATION (FAA) IS WORKING WITH THE DEPARTMENT OF DEFENSE (DOD) AND THE NATIONAL AERONAUTICS AND SPACE ADMINISTRATION (NASA) TO ENSURE THAT THE MOST CURRENT RE-ENTRY INFORMATION IS PROVIDED TO OPERATORS AS QUICKLY AS POSSIBLE. FURTHER NOTAMS WILL BE ISSUED IF SPECIFIC INFORMATION BECOMES AVAILABLE INDICATING A UNITED STATES (US) AIRSPACE IMPACT. IN THE INTEREST OF FLIGHT SAFETY, IT IS CRITICAL THAT ALL PILOTS/FLIGHT CREW MEMBERS REPORT ANY OBSERVED FALLING SPACE DEBRIS TO THE APPROPRIATE ATC FACILITY AND INCLUDE POSITION, ALTITUDE, TIME, AND DIRECTION OF DEBRIS OBSERVED. THE DOMESTIC EVENTS NETWORK /DEN/ TELEPHONE 202-493-5107, IS THE FAA COORDINATION FACILITY
Friday, 21 October 2011
Gearing up for ROSAT's re-entry, and an older observation of a Breeze-M tank near M31
Shortly after UARS, another satellite about to reenter is in the news: ROSAT. I last observed and photographed it about a week ago (see here and here) - since then, passes have become unfavourable for the Netherlands.
In an interesting twist, Sky & Telescope's J. Kelly Beatty reports that DLR and ESA sources confirmed to him that they expect the entire telescope mirror array - which weights 1.6 tons! - to survive reentry, impacting intact!
Various modellers now project the reentry to occur on October 23rd. Here is a short list of what various sources currently predict [editted 12:10 UTC, Oct 21, with latest Molczan update):
Space-Track (SSC): 23 Oct, 05:49 UTC (+/- 24 hrs)
Harro Zimmer: 23 Oct, 05:03 UTC (+/- 48 hrs)
Ted Molczan (using SatEvo): 23 Oct, 05:00 UTC (+/- 10 hrs) [editted]
Aerospace Corp.: 23 Oct, 13:24 UTC (+/- 16 hrs)
Since Ted uses the same software I used for my UARS predictions, and hence our results will be similar, I will not put forward my own predictions here but refer to Ted's.
A Breeze-M near M31, the Andromeda nebula
In my post of October 2nd, I featured an image I took on 29 September of a Russian Proton upper stage Breeze-M tank near the trail of USA 129. I wrote that:
Several satellites showed up on the image series, including a Breeze-M tank again, this time 2006-056B:
Here is the final image of M31, a stack of 105 individual 10 second images:
Given that this image was taken from a town center with modest equipment, I am quite happy with it! If you compare it to a single frame image (above) it shows the strong improvement in signal-to-noise ratio that comes from stacking images.The two satellite galaxies come out much better, and so does a glimpse of the spiral structure and dust bands in the Andromeda galaxy.
In an interesting twist, Sky & Telescope's J. Kelly Beatty reports that DLR and ESA sources confirmed to him that they expect the entire telescope mirror array - which weights 1.6 tons! - to survive reentry, impacting intact!
Various modellers now project the reentry to occur on October 23rd. Here is a short list of what various sources currently predict [editted 12:10 UTC, Oct 21, with latest Molczan update):
Space-Track (SSC): 23 Oct, 05:49 UTC (+/- 24 hrs)
Harro Zimmer: 23 Oct, 05:03 UTC (+/- 48 hrs)
Ted Molczan (using SatEvo): 23 Oct, 05:00 UTC (+/- 10 hrs) [editted]
Aerospace Corp.: 23 Oct, 13:24 UTC (+/- 16 hrs)
Since Ted uses the same software I used for my UARS predictions, and hence our results will be similar, I will not put forward my own predictions here but refer to Ted's.
A Breeze-M near M31, the Andromeda nebula
In my post of October 2nd, I featured an image I took on 29 September of a Russian Proton upper stage Breeze-M tank near the trail of USA 129. I wrote that:
These pieces of Russian space debris pop up more often on my images lately. They are the jettisonable torroidal (doughnut-shaped) fuel tanks of a Breeze-M, the upper stage of a Proton M. There are now over 40 of these spent empty tanks in space, often in highly elliptic orbits representative of a geostationary transfer.Just a few days later, on October 2nd, I took advantage of clear skies to image M31, the Andromeda galaxy. The camera (Canon EOS 450D) with the Samyang 1.4/85mm lens was piggybacked on a Meade ETX-70 in order to use the telescope drive to follow the stars. A long series of 10 second images was taken.
Several satellites showed up on the image series, including a Breeze-M tank again, this time 2006-056B:
click image to enlarge
Here is the final image of M31, a stack of 105 individual 10 second images:
click image to enlarge
Given that this image was taken from a town center with modest equipment, I am quite happy with it! If you compare it to a single frame image (above) it shows the strong improvement in signal-to-noise ratio that comes from stacking images.The two satellite galaxies come out much better, and so does a glimpse of the spiral structure and dust bands in the Andromeda galaxy.
Saturday, 15 October 2011
Another ROSAT observation
Yesterday evening was clear, and I again observed the doomed satellite ROSAT (see my previous post), in deep twilight (sun at -6 degrees). It was again bright, magnitude +1, very fast, easy to see even though the sky was still bright blue with only a few stars visible. Like my earlier observation the day before yesterday, it was steady in brightness, with no sign of brightness variations, suggesting it is not tumbling.
Photographically it was a challenge: I had to do some serious image editing tricks to pull the trail out of the bright twilight background on the image below (on the unedited image, the trail is visible but very inconspicuous):
These high elevation (near 70 degrees) twilight passes are quickly moving earlier (and too early) in the evening for me: yesterday's was the last one I could expect to realistically observe. Passes at lower elevation (12-14 degrees) in late twilight will become visible for me after tomorrow and might allow me to observe it for a few more days later this week, until these passes move too early as well.
Using Alan Pickup's SatEvo software and the current 10.7cm solar flux, I get a projected decay at October 23. Harro Zimmer, using another model, gets October 24th. These predictions still have an uncertainty of a few days, so expect them to shift over the coming days, amongst others due to changing solar activity.
Photographically it was a challenge: I had to do some serious image editing tricks to pull the trail out of the bright twilight background on the image below (on the unedited image, the trail is visible but very inconspicuous):
click image to enlarge
These high elevation (near 70 degrees) twilight passes are quickly moving earlier (and too early) in the evening for me: yesterday's was the last one I could expect to realistically observe. Passes at lower elevation (12-14 degrees) in late twilight will become visible for me after tomorrow and might allow me to observe it for a few more days later this week, until these passes move too early as well.
Using Alan Pickup's SatEvo software and the current 10.7cm solar flux, I get a projected decay at October 23. Harro Zimmer, using another model, gets October 24th. These predictions still have an uncertainty of a few days, so expect them to shift over the coming days, amongst others due to changing solar activity.
Thursday, 13 October 2011
Observing another doomed satellite: ROSAT
Shortly after the UARS reentry, which got wide attention, another scientific satellite is about to meet its demise by an uncontrolled plunge into the atmosphere. It is the German X-ray astronomical satellite ROSAT. This satellite is currently predicted to reenter about October 22 to 24.
This evening I watched it pass during twilight (sun at 8 degrees below the horizon, first stars just visible in a blue sky). It was fast, zipping across the sky, and bright: magnitude +1 and an easy naked eye object.
I used the new EF 2.0/35mm lens (a new purchase, first used last weekend during the Draconid meteor outburst, on which I will post in a later post), set to F2.5, making 5 second exposures at 400 ISO. The fast moving objects ran out of the frame of two of the three images. Below is the image thats shows the complete trail. The satellite was moving from left to right, across Cepheus. The streak in top is a streak of cirrus.
This evening I watched it pass during twilight (sun at 8 degrees below the horizon, first stars just visible in a blue sky). It was fast, zipping across the sky, and bright: magnitude +1 and an easy naked eye object.
I used the new EF 2.0/35mm lens (a new purchase, first used last weekend during the Draconid meteor outburst, on which I will post in a later post), set to F2.5, making 5 second exposures at 400 ISO. The fast moving objects ran out of the frame of two of the three images. Below is the image thats shows the complete trail. The satellite was moving from left to right, across Cepheus. The streak in top is a streak of cirrus.
click image to enlarge
Wednesday, 28 September 2011
Tracking stations along UARS final track - a reconstruction [UPDATED TWICE]
click map (revised version) to enlarge
Above map provides an overview of groundbased tracking stations in the ESA ESTRACK and the US AFSCN network that are near or on the final trajectory of UARS. For relevant trackings tations, times of Advance of Sight (AOS) or Loss of Sight (LOS) are indicated. UARS is depicted at the point of reentry (see previous post) as indicated by SSC.
From the NASA talk by Johnson, they pinpointed the 04:00 +/- 1 minute UTC time and 14.1 S, 170.2 W location of UARS's demise using detections and non-detections by "a number of sensors".
As can be seen on the map, none of the regular tracking stations had direct coverage of the reported reentry location, begging the question where the "large number of detections" NASA's Johnson was talking about comes from. UARS could first have shown up at the Kaena Point tracking facility in Hawaii at 4:07 UTC. At that time, it would have been without groundbased tracking for quite some time already (over half an orbit).
Of course, we cannot exclude that a temporary tracking facility (e.g. an AEGIS ship) was employed in Polynesia at the time, providing additional data.
Also, a reader of this blog wrote to me with the suggestion that the US Navy's sensitive network of hydrophones could have picked up a signal when wreckage hit sea surface. I have no idea how feasible that is.
I still feel space-based observations were possibly involved (see my earlier post here), but are not being publicly acknowledged. The early warning satellites DSP F20, DSP F16 and SBIRS Geo-1 would have had coverage of the reentry location.
(note added: if anyone knows of additional tracking stations along the trajectory, info is welcome)
Infrasound?
Note added 29 Sept 2011
Dan Fischer raised the option in the comments that Infrasound detections could be involved. Indeed, this is a possibility (I consulted a Dutch infrasound researcher for an opinion here, and he thinks it is feasible, especially if sonic booms were involved) even though the distances to infrasound arrays involved are large.
A number of infrasound arrays are scattered over the Pacific area, listening for possible atomic detonations in breach of the Nuclear Test Ban treaty. A map of them can be found here. In the wider area, such arrays are located on Tahiti (French Polynesia), Hawaii, the Marquesas and New Caledonia. The UARS reentry location is within this triangular area. Below is a map of infrasound detection arrays located in the Pacific around the published UARS reentry location.
Edit late 29 Sept: Dutch infrasound researcher Läslo Evers just notified me he has checked the Tahiti and New Caledonia infrasound records for the reentry - he finds no sign of it.
click map to enlarge
UARS reentered over Samoa? [slightly updated]
USSTRATCOM, followed later today by NASA, has released a new reentry time and location estimate for UARS. It puts the time at 04:00 +/- 1 minute UTC and location at 14.1 deg South, 170.2 degrees W. This is over the south-central Pacific, in the vicinity of Samoa.
The time and location is said to be based on a number of detections and non-detections of several "sensors", without clear indication whether these are groundbased or space based sensors (see my previous post here) but I do suspect the latter are involved. The more so since the only ground-based tracking stations in this wide area are on Oahu (Hawaii), Kwajalein and Guam, and none of these would be able to pinpoint this location so exactly as this location is out of their detection range [edit 28 Sep: plus, the final UARS track did not bring it in reach of Guam and Kwajalein anyway]. The description by NASA's Johnson in the video appears deliberately vague to me. [edit 28 Sep: there is of course always the possibility that they happened to have a tracking ship in the vicinity].
I have some lingering concern in the back of my mind about the "neatness" of a reentry at exactly 4:00 UTC (nice and round), but sometimes such coincidences do happen.
Below is a map of the now released reentry point.
The time and location is said to be based on a number of detections and non-detections of several "sensors", without clear indication whether these are groundbased or space based sensors (see my previous post here) but I do suspect the latter are involved. The more so since the only ground-based tracking stations in this wide area are on Oahu (Hawaii), Kwajalein and Guam, and none of these would be able to pinpoint this location so exactly as this location is out of their detection range [edit 28 Sep: plus, the final UARS track did not bring it in reach of Guam and Kwajalein anyway]. The description by NASA's Johnson in the video appears deliberately vague to me. [edit 28 Sep: there is of course always the possibility that they happened to have a tracking ship in the vicinity].
I have some lingering concern in the back of my mind about the "neatness" of a reentry at exactly 4:00 UTC (nice and round), but sometimes such coincidences do happen.
Below is a map of the now released reentry point.
click map to enlarge
Monday, 26 September 2011
Could the reentry of UARS have been monitored from Space?
One of the open questions regarding the inability to pinpoint the exact location and time of the UARS reentry, is whether the US military might have space-based detections from their infra-red early warning satellites.
The US military operates two constellations of such satellites, whose purpose is to detect and provide early warning for enemy ICBM launches using infra-red detection sensors. The older constellation is the DSP (Defense Support Program) series of satellites in geostationary orbit. There is also the newer SBIRS (Space-Based Infrared System) constellation, consisting of one geostationary satellite (SBIRS Geo-1) and two SBIRS sensors piggybacked on HEO satellites (USA 184 and USA 200).
We know that the DSP satellites have, in the past, frequently observed meteoric fireballs. It is therefore widely believed (and indeed likely) that the system should have been able to detect the UARS reentry fireballs as well. The problem is that post-9/11 the DoD has stopped declassifying meteor detections (which were previously shared with meteor scientists). Which makes you wonder whether, if they did detect the UARS reentry fireball, they would be forthcoming with that information. Probably not.
Would the UARS reentry have been visible from one of the DSP or SBIRS satellites? Would they cover the relevant areas? Yes they would.
Below map shows the location (for 4:16 UTC [edit 28 Sep: this was written before the reentry time was revised to 4:00 UTC, see here]) of UARS plus it's track, and the locations of the relevant satellites.
Yellow dots are the block 5 DSP satellites, white dots the SBIRS satellites. The green circle outlines show the coverage area of DSP F16, DSP F20, and SBIRS Geo-1.
The DSP's and SBIRS GEO-1 are geostationary and hence always above the geographic spot depicted in the map (with some minor latitudinal variation): for the HEO SBIRS platforms USA 184 and USA 200 the position plotted is for 4:16 UTC.At that time USA 184 was near apogee and basically almost in the same position (in geographic subsatellite point terms) for an hour on each side of 4:16 UTC. USA 200 was moving towards perigee, but would have UARS in view during the whole Africa pass of the latter.
DSP F16, DSP F20, SBIRS GEO-1 over the eastern Pacific as well as the SBIRS platform USA 184 over Siberia would cover the approach track over the Pacific and nominal center of the reentry window of UARS. Basically, they cover UARS on it's final track from New Zealand to over Canada.
Beyond Canada (would UARS have survived well beyond 4:16 UTC), DSP F17 over Brasil and the SBIRS platform USA 200 moving over Africa would have taken over, joined by DSP F18 plus DSP F21 and DSP F22 (all over Africa or the Indian Ocean) once over Africa.
I also checked whether the experimental satellites in the STSS (Space Tracking and Surveillance System) series would have been able to capture it: turns out they would not have, as these satellites (in low earth orbits) were not near the relevant part of the UARS track at that time.
In conclusion: there is plenty of possibilities for the US military to have detected the UARS reentry from space, using their space-based assets (DSP and SBIRS) in GEO and HEO. Even if groundbased tracking facilities were sparse over UARS' final track, the space-based sensors should have been able to observe and pinpoint the reentry.
Yet, I suspect that if these observations exist (allowing the DoD a clear indication as to where UARS debris might have showered down), this information will not be released to the public.
(text slightly editted 27 Sep to clarify USA 200 movement)
The US military operates two constellations of such satellites, whose purpose is to detect and provide early warning for enemy ICBM launches using infra-red detection sensors. The older constellation is the DSP (Defense Support Program) series of satellites in geostationary orbit. There is also the newer SBIRS (Space-Based Infrared System) constellation, consisting of one geostationary satellite (SBIRS Geo-1) and two SBIRS sensors piggybacked on HEO satellites (USA 184 and USA 200).
We know that the DSP satellites have, in the past, frequently observed meteoric fireballs. It is therefore widely believed (and indeed likely) that the system should have been able to detect the UARS reentry fireballs as well. The problem is that post-9/11 the DoD has stopped declassifying meteor detections (which were previously shared with meteor scientists). Which makes you wonder whether, if they did detect the UARS reentry fireball, they would be forthcoming with that information. Probably not.
Would the UARS reentry have been visible from one of the DSP or SBIRS satellites? Would they cover the relevant areas? Yes they would.
Below map shows the location (for 4:16 UTC [edit 28 Sep: this was written before the reentry time was revised to 4:00 UTC, see here]) of UARS plus it's track, and the locations of the relevant satellites.
click map to enlarge
Yellow dots are the block 5 DSP satellites, white dots the SBIRS satellites. The green circle outlines show the coverage area of DSP F16, DSP F20, and SBIRS Geo-1.
The DSP's and SBIRS GEO-1 are geostationary and hence always above the geographic spot depicted in the map (with some minor latitudinal variation): for the HEO SBIRS platforms USA 184 and USA 200 the position plotted is for 4:16 UTC.At that time USA 184 was near apogee and basically almost in the same position (in geographic subsatellite point terms) for an hour on each side of 4:16 UTC. USA 200 was moving towards perigee, but would have UARS in view during the whole Africa pass of the latter.
DSP F16, DSP F20, SBIRS GEO-1 over the eastern Pacific as well as the SBIRS platform USA 184 over Siberia would cover the approach track over the Pacific and nominal center of the reentry window of UARS. Basically, they cover UARS on it's final track from New Zealand to over Canada.
Beyond Canada (would UARS have survived well beyond 4:16 UTC), DSP F17 over Brasil and the SBIRS platform USA 200 moving over Africa would have taken over, joined by DSP F18 plus DSP F21 and DSP F22 (all over Africa or the Indian Ocean) once over Africa.
I also checked whether the experimental satellites in the STSS (Space Tracking and Surveillance System) series would have been able to capture it: turns out they would not have, as these satellites (in low earth orbits) were not near the relevant part of the UARS track at that time.
In conclusion: there is plenty of possibilities for the US military to have detected the UARS reentry from space, using their space-based assets (DSP and SBIRS) in GEO and HEO. Even if groundbased tracking facilities were sparse over UARS' final track, the space-based sensors should have been able to observe and pinpoint the reentry.
Yet, I suspect that if these observations exist (allowing the DoD a clear indication as to where UARS debris might have showered down), this information will not be released to the public.
(text slightly editted 27 Sep to clarify USA 200 movement)
Sunday, 25 September 2011
"UARS crash" at Okotoks Alberta (Canada) now confirmed to be hoax
After all the hectic of the previous night, I spent yesterday out of house in the dunes and near the beach. Time to pick up now where I left.
NASA has held a teleconference. Basically, they did not report anything new regarding the potential reentry location than what I already reported here based on SSC and Harro Zimmer's conclusions. Note that this NASA map released is basically the same I posted here earlier.
I don't share some of the critique currently levelled at NASA. See discussion at the end of this post.
Okotoks, Canada: a HOAX
The Okotoks (Alberta, Canada) video and report of debris being found (see earlier post here) - news media now report it is a HOAX. Seems I was right with having my reservations. [update 26 sep: more here. The report on wreckage was a hoax created by an aspiring film maker, apparently]
Aircraft contrails being mistaken for UARS
Meanwhile, simple aircraft contrails keep being mistaken for UARS as well: see the previous post and another case here.
Radar artefacts being mistaken for UARS
This one that is doing the rounds, is a mis-interpretation of a very common weather radar artefact. Note how the streak neatly points to the radar origin in the center.
Chinese lantern balloons being presented as "UARS"
As I pointed out in the previous post, footage of Chinese lantern balloons are either deliberately or mistakenly being passed off as "UARS" in the media as well.
Possible confusion with meteoric fireballs
To complicate the picture, there is also the point that "normal" meteoric fireballs appear and can be mistaken for UARS. Multiple such fireballs occur somewhere on this world every day.
Indeed, we had a very nice meteoric firebal (seen by amongst others myself while waiting for the UARS pass) of mag. -5 appear 5 minutes before the 1:37 UTC UARS pass on the 24th. Klaas Jobse has a nice all-sky image of that one here. Yet another one appeared a mere 17 minutes later (video of both fireballs here, again by Klaas Jobse). These were meteoric fireballs, little bits of asteroid or comet debris not related to UARS at all.
While it didn't fool experienced observers like me, laypersons could have easily mistaken it for UARS debris.
Some genuine reports of bright fireball phenomena seen around the predicted reentry time from a.o. Canada, could be such cases of meteoric fireballs. Without clear details on duration and character, it is difficult to discern between these and any potential real reentry observations.
Critique on NASA: I don't share that critique
There is currently a lot of critique on NASA that they can't pinpoint the point of reentry. I think those critiques are unfounded and stem from unrealistic expectations.
All I can say is: people expect too much of NASA and modern technology, notably under the influence of unrealistic TV-series that depict NASA as know-it-alls that can do anything (with just a few computer keystrokes and maybe a hack into a satellite feed here and there typically, according to the TV series that increasingly mold the public's "reality").
But even the best technology and best experts have their limits (and in terms of the actual tracking, this technology is not operated by NASA, but by the US Air Force, by the way), and with the last few UARS revolutions largely over empty ocean devoid of tracking stations, things simply get difficult. There are limits to what models can do when devoid of real-time tracking sensor input.
I might, given time and energy, elaborate on that later in a separate post
NASA has held a teleconference. Basically, they did not report anything new regarding the potential reentry location than what I already reported here based on SSC and Harro Zimmer's conclusions. Note that this NASA map released is basically the same I posted here earlier.
I don't share some of the critique currently levelled at NASA. See discussion at the end of this post.
Okotoks, Canada: a HOAX
The Okotoks (Alberta, Canada) video and report of debris being found (see earlier post here) - news media now report it is a HOAX. Seems I was right with having my reservations. [update 26 sep: more here. The report on wreckage was a hoax created by an aspiring film maker, apparently]
Aircraft contrails being mistaken for UARS
Meanwhile, simple aircraft contrails keep being mistaken for UARS as well: see the previous post and another case here.
Radar artefacts being mistaken for UARS
This one that is doing the rounds, is a mis-interpretation of a very common weather radar artefact. Note how the streak neatly points to the radar origin in the center.
Chinese lantern balloons being presented as "UARS"
As I pointed out in the previous post, footage of Chinese lantern balloons are either deliberately or mistakenly being passed off as "UARS" in the media as well.
Possible confusion with meteoric fireballs
To complicate the picture, there is also the point that "normal" meteoric fireballs appear and can be mistaken for UARS. Multiple such fireballs occur somewhere on this world every day.
Indeed, we had a very nice meteoric firebal (seen by amongst others myself while waiting for the UARS pass) of mag. -5 appear 5 minutes before the 1:37 UTC UARS pass on the 24th. Klaas Jobse has a nice all-sky image of that one here. Yet another one appeared a mere 17 minutes later (video of both fireballs here, again by Klaas Jobse). These were meteoric fireballs, little bits of asteroid or comet debris not related to UARS at all.
While it didn't fool experienced observers like me, laypersons could have easily mistaken it for UARS debris.
Some genuine reports of bright fireball phenomena seen around the predicted reentry time from a.o. Canada, could be such cases of meteoric fireballs. Without clear details on duration and character, it is difficult to discern between these and any potential real reentry observations.
Critique on NASA: I don't share that critique
There is currently a lot of critique on NASA that they can't pinpoint the point of reentry. I think those critiques are unfounded and stem from unrealistic expectations.
All I can say is: people expect too much of NASA and modern technology, notably under the influence of unrealistic TV-series that depict NASA as know-it-alls that can do anything (with just a few computer keystrokes and maybe a hack into a satellite feed here and there typically, according to the TV series that increasingly mold the public's "reality").
But even the best technology and best experts have their limits (and in terms of the actual tracking, this technology is not operated by NASA, but by the US Air Force, by the way), and with the last few UARS revolutions largely over empty ocean devoid of tracking stations, things simply get difficult. There are limits to what models can do when devoid of real-time tracking sensor input.
I might, given time and energy, elaborate on that later in a separate post
Saturday, 24 September 2011
False "UARS" video's
Some video's are doing the rounds, some in respected news media, purporting to be showing the demise of UARS but in reality definitely something else.
This one posted on Space.com is an example. This clearly shows a Chinese lantern balloon, not UARS: you can see the bag and burner.
Another one is here (with thanks to Dan Fischer for pointing me to it): this British video on the website of The Telegraph simply shows an aircraft with contrail. As science writer Dan Fischer remarked in despair about this one on twitter: "don't you people ever watch the sky?!". Indeed, one would expect people recognize aircraft and contrails these days. Yet we see them pop up time and again in the media, as purported footage of "fireballs" and now as "UARS".
There is more of this stuff doing the rounds on the intarwebz currently. So be very careful with purported footage and images of "UARS reentering". A lot is not what it seems.
This one posted on Space.com is an example. This clearly shows a Chinese lantern balloon, not UARS: you can see the bag and burner.
Another one is here (with thanks to Dan Fischer for pointing me to it): this British video on the website of The Telegraph simply shows an aircraft with contrail. As science writer Dan Fischer remarked in despair about this one on twitter: "don't you people ever watch the sky?!". Indeed, one would expect people recognize aircraft and contrails these days. Yet we see them pop up time and again in the media, as purported footage of "fireballs" and now as "UARS".
There is more of this stuff doing the rounds on the intarwebz currently. So be very careful with purported footage and images of "UARS reentering". A lot is not what it seems.
UARS update 24 Sept (2) - so where did it crash?!?
It is still not entirely clear where and when UARS met a fiery end. SSC issued a bulletin stating 4:16 +/- 53 minutes UTC. Harro Zimmer issued a final prediction of 4:15 +/- 9 minutes UTC.
The latter would place the reentry over an area defined by the Northeast Pacific and northern Canada.
The problem is that the reentry was (according to a lack of reliable reports so far) not unambiguously observed, and probably that the last revolutions took UARS over areas (oceans and central Africa) where tracking stations are sparse. Perhaps the DoD might have space-based observations from their Infrared early warning satellites, but the question is whether those data will become public or not.
Okotoks video - UARS or not?
Meanwhile, a video from Okotoks, Alberta, Canada, hit the internet, purporting to show fireballs from the UARS reentry. However, to many people including me the video does not look right.
We feel it looks more like a series of "Chinese lanterns", small toy hot air balloons. The individual "fragments" just don't show enough evolution over the video, they are too steady, amongst others (also, in the video the guy shooting it says it is "September 22nd", a wrong date).
I could be wrong though, and the general geographic area is in line with the predictions. So while I don't want to write off the video completely, I do keep my reservations about it.
UPDATE 11:25 UTC: there is now an UNCONFIRMED report of debris pieces having been found near where the video was taken. No details, no pictures, so could be bogus or mistake, no way to say.
The latter would place the reentry over an area defined by the Northeast Pacific and northern Canada.
click map to enlarge
The problem is that the reentry was (according to a lack of reliable reports so far) not unambiguously observed, and probably that the last revolutions took UARS over areas (oceans and central Africa) where tracking stations are sparse. Perhaps the DoD might have space-based observations from their Infrared early warning satellites, but the question is whether those data will become public or not.
Okotoks video - UARS or not?
Meanwhile, a video from Okotoks, Alberta, Canada, hit the internet, purporting to show fireballs from the UARS reentry. However, to many people including me the video does not look right.
We feel it looks more like a series of "Chinese lanterns", small toy hot air balloons. The individual "fragments" just don't show enough evolution over the video, they are too steady, amongst others (also, in the video the guy shooting it says it is "September 22nd", a wrong date).
I could be wrong though, and the general geographic area is in line with the predictions. So while I don't want to write off the video completely, I do keep my reservations about it.
UPDATE 11:25 UTC: there is now an UNCONFIRMED report of debris pieces having been found near where the video was taken. No details, no pictures, so could be bogus or mistake, no way to say.
UARS update, 24 Sept (1)
UARS reentry update, 24 Sept 02:00 UTC
click here to check for more recent updates
We are now probably less than 3 hours from UARS reentry.
Using SatEvo software and the latest few orbital updates, re-entry is projected for 24 Sept 4:20-5:05 UTC: in essence, 4:45 UT +/- half an hour. [next sentence corrected] This would indicate Africa and possibly Australia as places which might get to see it.[/corrected]
Watched the 01:37 UTC pass here: this UARS pass was with the satellite completely in earth shadow. Nothing was seen, which means it is not glowing yet.
To make up for missing the decay (this was the last realisticly visible UARS pass for me in the Netherlands), I was treated on a beautiful meteoric fireball at 01:32:44 UTC, at least magnitude -5 if not brighter, appearing due south. It moved through Cetus ending some 10-15 degrees above the horizon. Mediumfast, and with a wake.
This is probably my last pre-reentry UARS update: I am very tired (it is 4:15 am here), the show is over as far as the Netherlands is concerned, so I am going to bed and will see tomorrow morning where UARS came down.
click here to check for more recent updates
We are now probably less than 3 hours from UARS reentry.
Using SatEvo software and the latest few orbital updates, re-entry is projected for 24 Sept 4:20-5:05 UTC: in essence, 4:45 UT +/- half an hour. [next sentence corrected] This would indicate Africa and possibly Australia as places which might get to see it.[/corrected]
Watched the 01:37 UTC pass here: this UARS pass was with the satellite completely in earth shadow. Nothing was seen, which means it is not glowing yet.
To make up for missing the decay (this was the last realisticly visible UARS pass for me in the Netherlands), I was treated on a beautiful meteoric fireball at 01:32:44 UTC, at least magnitude -5 if not brighter, appearing due south. It moved through Cetus ending some 10-15 degrees above the horizon. Mediumfast, and with a wake.
This is probably my last pre-reentry UARS update: I am very tired (it is 4:15 am here), the show is over as far as the Netherlands is concerned, so I am going to bed and will see tomorrow morning where UARS came down.
click image to enlarge
Friday, 23 September 2011
UARS reentry update, 23 Sept (5)
UARS reentry update, 23 Sept 21:20 UTC
click here to check for more recent updates
SatEvo software with the latest orbital elements projects the re-entry at nominally 5:25 UTC (24th), so the time is slightly moving away again from 6+ UTC towards an earlier time.
Harro Zimmer predicts, using a more sophisticated model, 4:15 UTC +/- 90 minutes.
I covered the 21:05 UTC pass here, maximum altitude 57 degrees. It was a pass completely is shadow, so UARS would only be visible if it was already developing plasma phenomena. I did not see it (using both camera, and visually wityh 10 x 50 binoculars) so it isn't glowing yet.
click here to check for more recent updates
SatEvo software with the latest orbital elements projects the re-entry at nominally 5:25 UTC (24th), so the time is slightly moving away again from 6+ UTC towards an earlier time.
Harro Zimmer predicts, using a more sophisticated model, 4:15 UTC +/- 90 minutes.
I covered the 21:05 UTC pass here, maximum altitude 57 degrees. It was a pass completely is shadow, so UARS would only be visible if it was already developing plasma phenomena. I did not see it (using both camera, and visually wityh 10 x 50 binoculars) so it isn't glowing yet.
click diagram to enlarge
UARS reentry update 23 Sept (4)
UARS reentry update, 23 Sept 18:30 UTC
click here to check for more recent updates
SatEvo software with the latest orbital elements now suggests re-entry at about 5-6 UTC (24th).
Harro Zimmer, using a much more sophisticated model, suggests 3:45 UTC, +/- 90 minutes.
click here to check for more recent updates
SatEvo software with the latest orbital elements now suggests re-entry at about 5-6 UTC (24th).
Harro Zimmer, using a much more sophisticated model, suggests 3:45 UTC, +/- 90 minutes.
click diagram to enlarge
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