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.
Saturday, 24 September 2011
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
UARS reentry update 23 Sept (3)
UARS reentry update, 23 Sept 13:30 UTC
click here to check for more recent updates
The nominal projected times for the UARS decay are moving forward again, to later times (which is less favourable for Europe). The latest three orbits at the moment of writing suggest times between 2 UT and 3:45 UT on the 24th.
click here to check for more recent updates
The nominal projected times for the UARS decay are moving forward again, to later times (which is less favourable for Europe). The latest three orbits at the moment of writing suggest times between 2 UT and 3:45 UT on the 24th.
click diagram to enlarge
UARS reentry update Sep 23 (2)
UARS reentry update, 23 Sept 8:45 UTC
click here to check for more recent updates
New orbital update, time shifted forward by 2 hours again. Shows that the uncertainty is still many hours. Nominal time now 24 Sep 02:00 UTC, but moving somewhat towards the right direction (for me in the Netherlands) . Here's hoping it will eventually move to near 23 Sep 21 UT.....
click here to check for more recent updates
New orbital update, time shifted forward by 2 hours again. Shows that the uncertainty is still many hours. Nominal time now 24 Sep 02:00 UTC, but moving somewhat towards the right direction (for me in the Netherlands) . Here's hoping it will eventually move to near 23 Sep 21 UT.....
click diagram to enlarge
UARS reentry update 23 Sept (1)
UARS reentry update, 23 Sept 7:45 UTC
click here to check for more recent updates
The projected time of decay is still shifting considerabely with each orbit update: over the past 10 hours, it has hifted back and forth by several hours. The last few orbital updates tend to shift the projected reentry to a later time, early on the 24th, bringing a decay near the USA in view again
At the moment of writing, the nominal projected reentry time using SatEvo and current solar flux data is 4:15 UTC on the 24th. This still has an uncertainty of a couple of hours, though.
Below diagram depicts how the projected renetry time has fluctuated with each new orbit released over the past two days:
click here to check for more recent updates
The projected time of decay is still shifting considerabely with each orbit update: over the past 10 hours, it has hifted back and forth by several hours. The last few orbital updates tend to shift the projected reentry to a later time, early on the 24th, bringing a decay near the USA in view again
At the moment of writing, the nominal projected reentry time using SatEvo and current solar flux data is 4:15 UTC on the 24th. This still has an uncertainty of a couple of hours, though.
Below diagram depicts how the projected renetry time has fluctuated with each new orbit released over the past two days:
click diagram to enlarge
Thursday, 22 September 2011
The following UARS related NOTAM was posted by the FAA:
!FDC 1/2095 FDC .. SPECIAL NOTICE .. EFFECTIVE IMMEDIATELY UNTIL 1109252359 UTC. AIRCRAFT ARE ADVISED THAT A POTENTIAL HAZARD MAY OCCUR DUE TO REENTRY OF SATELLITE UARS INTO THE EARTH'S ATMOSPHERE. FURTHER NOTAMS WILL BE ISSUED IF SPECIFIC INFORMATION BECOMES AVAILABLE. 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.
UARS update, September 22 pm
UARS update 22 September 20:30 UTC
The projected decay time for UARS keeps shifting back and forth with each orbital update. Over the course of today, it has oscilated between 19:00 UT on the 23rd to 01:00 UT on the 24th.
The last few orbits tend to favour the later part of this time window, but it could as easily swing back to the earlier part of the window again over the course of tonight and tomorrow.
This just goes to show that the uncertainties are still large and still amount to many hours. Over the course of tomorrow, it will become gradually more clear. The current time window is however exciting, as we have passes visible from Europe including the Netherlands during that time span, notably around 21h UT.
The projected decay time for UARS keeps shifting back and forth with each orbital update. Over the course of today, it has oscilated between 19:00 UT on the 23rd to 01:00 UT on the 24th.
The last few orbits tend to favour the later part of this time window, but it could as easily swing back to the earlier part of the window again over the course of tonight and tomorrow.
This just goes to show that the uncertainties are still large and still amount to many hours. Over the course of tomorrow, it will become gradually more clear. The current time window is however exciting, as we have passes visible from Europe including the Netherlands during that time span, notably around 21h UT.
click diagram to enlarge
UARS update, Sept 22 am
UARS update 22 Sept 08:45 UTC
Re-entry of UARS is now projected on the 23rd. Latest orbit plus current solar flux and Alan Pickup's fine SatEvo software suggest a nominal time near 19:00 UTC on the 23rd, but at this time that still has an uncertainty of several hours (I suggest up to at least 6 hours).
Areas with the best chances to see the reentry are currently for a swat that includes South-America, Europe, Russia, central Asia, southeast Asia and Australia, which all have passes in the hours around the nominal predicted time. It is increasingly unlikely that the USA will get to see anything of it.
Re-entry of UARS is now projected on the 23rd. Latest orbit plus current solar flux and Alan Pickup's fine SatEvo software suggest a nominal time near 19:00 UTC on the 23rd, but at this time that still has an uncertainty of several hours (I suggest up to at least 6 hours).
Areas with the best chances to see the reentry are currently for a swat that includes South-America, Europe, Russia, central Asia, southeast Asia and Australia, which all have passes in the hours around the nominal predicted time. It is increasingly unlikely that the USA will get to see anything of it.
Wednesday, 21 September 2011
UARS update, September 21 pm
UARS update, 21 Sept, 20:00 UTC
Based on the latest orbital elements from Space-Track, the projected reentry time is slowly moving earlier. The nominal value is now late September 23 (nominal 20:30 UTC, but with still many, many hours uncertainty). But within uncertainties, early September 24 (in UTC terms) is certainly not yet out of the picture. A lot can still happen in the two days left, e.g. changes in solar activity.
Below is an updated diagram of the observed and predicted orbital evolution in terms of apogee and perigee altitudes.
Based on the latest orbital elements from Space-Track, the projected reentry time is slowly moving earlier. The nominal value is now late September 23 (nominal 20:30 UTC, but with still many, many hours uncertainty). But within uncertainties, early September 24 (in UTC terms) is certainly not yet out of the picture. A lot can still happen in the two days left, e.g. changes in solar activity.
Below is an updated diagram of the observed and predicted orbital evolution in terms of apogee and perigee altitudes.
click diagram to enlarge
Eternal circling of the sky - and a METOP-A flare
As I pointed out in my previous post, the evening of 19 September was reasonably clear (the odd streak of clouds every now and then).
After I observed USA 129 (and incidentally Topex flashing nicely, see previous post), I set up the camera with the automated wire release for a long series of images on the celestial pole, using the EF 2.8/24mm wide angle lens.
Result is above "classic" star trail image, showing the eternal circling of the sky around the celestial pole. It was constructed by stacking 165 images of 15 seconds each, shot over a time interval of 44 minutes. Note that the Polestar makes a small circle segment too - it is not exactly at the celestial pole.
The long crossing lines are aircraft (I am close to a major airport). The near-vertical trail in the upper left corner is a satellite flare however: the European weather satellite METOP-A (06-044A).
Below is a detail from the single image that showed the METOP-A flare (at about 20:37:55 UTC, 19 September). Very faintly, the double trail of a NOSS duo, NOSS 3-2 (03-054 A & C) can be seen as well. As this part of the image is close to the image edge, it suffers a bit from coma with this wide angle lens.
In the old days of analogue photography, a 44 minute star trail image like this would not have been possible from my urban locality: the image would have fogged too much. Modern digital and especially image stacking techniques, make it possible.
After I observed USA 129 (and incidentally Topex flashing nicely, see previous post), I set up the camera with the automated wire release for a long series of images on the celestial pole, using the EF 2.8/24mm wide angle lens.
click image to enlarge
Result is above "classic" star trail image, showing the eternal circling of the sky around the celestial pole. It was constructed by stacking 165 images of 15 seconds each, shot over a time interval of 44 minutes. Note that the Polestar makes a small circle segment too - it is not exactly at the celestial pole.
The long crossing lines are aircraft (I am close to a major airport). The near-vertical trail in the upper left corner is a satellite flare however: the European weather satellite METOP-A (06-044A).
Below is a detail from the single image that showed the METOP-A flare (at about 20:37:55 UTC, 19 September). Very faintly, the double trail of a NOSS duo, NOSS 3-2 (03-054 A & C) can be seen as well. As this part of the image is close to the image edge, it suffers a bit from coma with this wide angle lens.
click image to enlarge
In the old days of analogue photography, a 44 minute star trail image like this would not have been possible from my urban locality: the image would have fogged too much. Modern digital and especially image stacking techniques, make it possible.
Topex/Poseidon flaring
Monday evening was clear. I targetted the KH-12 Keyhole USA 129 - it is expected to manoeuvre one of these days.
While watching it (and photographing it), a bright mag. +0.5 flash occurred close to it, followed by another one and than a longer +1.5 flare. It turned out to be the malfunctioned US-French Oceanographic satellite Topex/Poseidon (92-052A), which I have observed flashing before. It malfunctioned in 2006 and since has started to tumble.
Below is the image showing both USA 129 and Topex/Poseidon, the latter showing the three flares:
The image yields this brightness curve, with peaks (two narrow and one broad) spaced 3.6 seconds apart:
While watching it (and photographing it), a bright mag. +0.5 flash occurred close to it, followed by another one and than a longer +1.5 flare. It turned out to be the malfunctioned US-French Oceanographic satellite Topex/Poseidon (92-052A), which I have observed flashing before. It malfunctioned in 2006 and since has started to tumble.
Below is the image showing both USA 129 and Topex/Poseidon, the latter showing the three flares:
click image to enlarge
The image yields this brightness curve, with peaks (two narrow and one broad) spaced 3.6 seconds apart:
click diagram to enlarge
UARS update 21 Sept am
Note: forecast and diagram now superceded by update here.
All eyes of the satellite world are now firmly on UARS. Unfortunately, I have no visible passes here these last few days of its existence.
The predictions for the moment of re-entry keep fluctuating between late September 23 and early September 24. Using Alan Pickup's SatEvo software and a 10.7 cm solar flux value of 145 plus this morning's latest elset, the nominal prediction is for the early hours of September 24 but this time still has an uncertainty of up to half a day.
Below diagram shows the changes in apogee altitudes (blue) and perigee altitudes (red) of UARS over September, plus a forecast of the future evolution of them (grey) untill re-entry.
All eyes of the satellite world are now firmly on UARS. Unfortunately, I have no visible passes here these last few days of its existence.
The predictions for the moment of re-entry keep fluctuating between late September 23 and early September 24. Using Alan Pickup's SatEvo software and a 10.7 cm solar flux value of 145 plus this morning's latest elset, the nominal prediction is for the early hours of September 24 but this time still has an uncertainty of up to half a day.
Below diagram shows the changes in apogee altitudes (blue) and perigee altitudes (red) of UARS over September, plus a forecast of the future evolution of them (grey) untill re-entry.
click diagram to enlarge
Monday, 19 September 2011
USA 129 with a Chinese rocket, and a failed attempt for a last view of UARS
Yesterday afternoon it cleared fantastically. In the evening, I targetted the KH-12 Keyhole USA 129 (96-072A), which I also observed on the 11th and 14th under much more challenging conditions.
USA 129 had some confusion in store: at the moment it appeared from behind the roof on its ascending trajectory, not one but two bright objects appeared, side by side and moving more or less parallel.
One of the objects (the westernmost one) moved slightly faster than the other. It was a Chinese Long March rocket booster, CZ-2C r/b (09-061B) used to launch the SJ-11-01 experimental satellite.
USA 129 itself next slowly flared to mag. +0.5 at about 19:35:05 UTC.
The first image showed, besides USA 129 and CZ-2C r/b, yet a third, very faint trail. It didn't match any known object. After some enhancing and looking at it in detail, I think it is actually a meteor, not a satellite. As my attention was to the bright and unexpected USA 129/CZ-2C r/b chance duo, I did not see the object visually.
In the early morning, UARS, now only days from re-entry, would make a pass emerging from earth shadow at 20 degrees altitude under Orion near 3:50 UTC (5:50 am local time). This was probably my last chance to see it before re-entry.
When I woke up and checked the sky it was clear apart from a field of clouds in the northwest. Grabbing my gear, patches of clouds unfortunately moved in south as well. Short story: patch of clouds right under Orion right at the moment UARS would pass....so UARS not seen, alas.
The expected decay of UARS is moving more and more forward in time, and is now set for the second half of September 23rd.
USA 129 had some confusion in store: at the moment it appeared from behind the roof on its ascending trajectory, not one but two bright objects appeared, side by side and moving more or less parallel.
click image to enlarge
One of the objects (the westernmost one) moved slightly faster than the other. It was a Chinese Long March rocket booster, CZ-2C r/b (09-061B) used to launch the SJ-11-01 experimental satellite.
USA 129 itself next slowly flared to mag. +0.5 at about 19:35:05 UTC.
The first image showed, besides USA 129 and CZ-2C r/b, yet a third, very faint trail. It didn't match any known object. After some enhancing and looking at it in detail, I think it is actually a meteor, not a satellite. As my attention was to the bright and unexpected USA 129/CZ-2C r/b chance duo, I did not see the object visually.
In the early morning, UARS, now only days from re-entry, would make a pass emerging from earth shadow at 20 degrees altitude under Orion near 3:50 UTC (5:50 am local time). This was probably my last chance to see it before re-entry.
When I woke up and checked the sky it was clear apart from a field of clouds in the northwest. Grabbing my gear, patches of clouds unfortunately moved in south as well. Short story: patch of clouds right under Orion right at the moment UARS would pass....so UARS not seen, alas.
The expected decay of UARS is moving more and more forward in time, and is now set for the second half of September 23rd.
Friday, 16 September 2011
UARS re-entry Update (and Nanosail-D, and IGS 1B)
UARS update: It seems that the re-entry moment for UARS, the defunct NASA Upper Atmosphere Research Satellite, is moving forward in time, as Harro Zimmer pointed out on the Seesat-L list.
NASA and SSC Space-Track both settle for a decay on or near 24 September, and so do independant analysis by Harro Zimmer as well as my own assessment (using Alan Pickup's SatEvo software with current 10.7cm flux values).
As the orbital development near decay is highly influenced by solar activity, there currently is an uncertainty of possibly up to a few days in these predictions. Yet it seems save to say that UARS has not much more than a week left.
Nanosail-D update: Meanwhile, that other NASA object up there slowly coming down, NASA's experimental solar sail Nanosail-D, seems not quite willing to give up. It's current orbit and current values for 10.7cm solar flux suggest it will hang on at least another month, untill late October. Same caveats as for UARS apply.
IGS 1B update: this defunct Japanese spy satellite which is steadily coming down (see earlier post here and earlier posts linked their in) since it malfunctioned in 2007, likewise seems intend on spending some more time up there. The current orbit plus solar activity now give a nominal re-entry prognosis for early 2013 instead of 2012. This date is certainly still going to shift back or forth considerably however, depending on how solar activity develops.
NASA and SSC Space-Track both settle for a decay on or near 24 September, and so do independant analysis by Harro Zimmer as well as my own assessment (using Alan Pickup's SatEvo software with current 10.7cm flux values).
As the orbital development near decay is highly influenced by solar activity, there currently is an uncertainty of possibly up to a few days in these predictions. Yet it seems save to say that UARS has not much more than a week left.
Nanosail-D update: Meanwhile, that other NASA object up there slowly coming down, NASA's experimental solar sail Nanosail-D, seems not quite willing to give up. It's current orbit and current values for 10.7cm solar flux suggest it will hang on at least another month, untill late October. Same caveats as for UARS apply.
IGS 1B update: this defunct Japanese spy satellite which is steadily coming down (see earlier post here and earlier posts linked their in) since it malfunctioned in 2007, likewise seems intend on spending some more time up there. The current orbit plus solar activity now give a nominal re-entry prognosis for early 2013 instead of 2012. This date is certainly still going to shift back or forth considerably however, depending on how solar activity develops.
Thursday, 15 September 2011
Wednesday's fireball over the US southwest was not UARS
A brilliant fireball was seen and filmed over the US southwest (Arizona, Nevada and California) last night. Some media suggest it could be connected to UARS, the US satellite about to plunge down in the atmosphere later this month.
It was definitely not UARS though. Not only was UARS still being tracked and hence in orbit after the fireball appeared (approx. 19:45 MST on the 14th, or 2:45 UTC on the 15th): but it was simply not passing over that part of the USA at that time. It was hence not UARS, or a piece of UARS.
It was definitely not UARS though. Not only was UARS still being tracked and hence in orbit after the fireball appeared (approx. 19:45 MST on the 14th, or 2:45 UTC on the 15th): but it was simply not passing over that part of the USA at that time. It was hence not UARS, or a piece of UARS.
Wednesday, 14 September 2011
USA 161 new orbit finally established
The saga earlier covered here and here is finally coming to an end: it seems that the KH-12 keyhole USA 161 now no longer is escaping our detection.
The reboost on August 24 has provided our observer's and analysts corps with quite a challenge. After initial failures to recover it, the satellite was detected by several observers (including me) for a number of times in the early days of September. But in each case it was subsequently lost again and each new preliminary orbit solution put forward seemed to be wrong (see the two posts linked above in the introduction). Analysts were in despair, and observers confused.
Then Ted finally found a solution which seemed to agree with all observations and asked observers to search according to this search orbit early this week. Following this, Scott Tilley in the USA indeed recovered the object in a position much as predicted by Ted's solution, with Russell Eberst in Scotland following suit.
The now established orbit is quite different from the earlier search orbits. Instead of the perigee having been raised, it turns out that it has been lowered, with the perigee 40 km lower and apogee 120 km lowered.
The reboost on August 24 has provided our observer's and analysts corps with quite a challenge. After initial failures to recover it, the satellite was detected by several observers (including me) for a number of times in the early days of September. But in each case it was subsequently lost again and each new preliminary orbit solution put forward seemed to be wrong (see the two posts linked above in the introduction). Analysts were in despair, and observers confused.
Then Ted finally found a solution which seemed to agree with all observations and asked observers to search according to this search orbit early this week. Following this, Scott Tilley in the USA indeed recovered the object in a position much as predicted by Ted's solution, with Russell Eberst in Scotland following suit.
The now established orbit is quite different from the earlier search orbits. Instead of the perigee having been raised, it turns out that it has been lowered, with the perigee 40 km lower and apogee 120 km lowered.
Saturday, 10 September 2011
Watch UARS - it's dropping!
Several news outlets are abuzz (e.g. here and here) about UARS, the defunct Upper Atmosphere Research Satellite, which is in the last days of its life.
Launched on Space Shuttle STS-48 in 1991, it was shut down in 2005 and it's orbit lowered to speed up decay.
That moment of decay is now near, with the 6 tonnes satellite expected to re-enter into our atmosphere in the last days of September or first days of October. At this moment , it is not possible to predict the moment of decay more exactly than this, and hence it is impossible to say where (over which part of the world) the re-entry will take place. At the moment of writing, the satellite already has come down to a 244 x 275 km orbit. The nominal decay date is currently projected to be around September 28-29 but has an uncertainty of several days.
UARS is that big, that parts of it might actually survive re-entry and impact on land or sea. Modelling by NASA suggests up to 532 kg of material, broken up into tens of pieces, might survive re-entry, with the biggest piece being perhaps in the order of just over 150 kg. The odds of this debris hitting someone are small however.
UARS is a large satellite that can be quite bright and easily seen by the naked eye: in the past, I have seen it attain brightnesses up to mag. +0.5, as bright as the brightest stars in the sky.
The image above shows UARS photographed by me on 16 June 2010 from Leiden, the Netherlands, when it showed a small flare.
click image to enlarge
Launched on Space Shuttle STS-48 in 1991, it was shut down in 2005 and it's orbit lowered to speed up decay.
That moment of decay is now near, with the 6 tonnes satellite expected to re-enter into our atmosphere in the last days of September or first days of October. At this moment , it is not possible to predict the moment of decay more exactly than this, and hence it is impossible to say where (over which part of the world) the re-entry will take place. At the moment of writing, the satellite already has come down to a 244 x 275 km orbit. The nominal decay date is currently projected to be around September 28-29 but has an uncertainty of several days.
UARS is that big, that parts of it might actually survive re-entry and impact on land or sea. Modelling by NASA suggests up to 532 kg of material, broken up into tens of pieces, might survive re-entry, with the biggest piece being perhaps in the order of just over 150 kg. The odds of this debris hitting someone are small however.
UARS is a large satellite that can be quite bright and easily seen by the naked eye: in the past, I have seen it attain brightnesses up to mag. +0.5, as bright as the brightest stars in the sky.
The image above shows UARS photographed by me on 16 June 2010 from Leiden, the Netherlands, when it showed a small flare.
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