UARS update 3: new predicted re-entry tonight at 03:16 UTC +/- 5 hrs

By Phil Plait | September 23, 2011 11:07 am

[UPDATE to the update (22:00 UTC): a new prediction just came out: tonight, September 23/24, at 04:04 UTC (midnight Eastern US time). The uncertainty is down to +/- 3 hours, and the location is the middle of the Pacific. Clicking the links below to CORDS or the image itself will take you to the most current prediction.]

The Center for Orbital and Reentry Debris Studies has updated their predicted re-entry time for NASA’s UARS satellite. It is now 9/24 (tonight!) at 03:16 UTC, which puts it over the Sahara:

Note that again this is later than the last estimate. As the satellite has gotten lower, aerodynamic drag — the wind blowing on it, tenuous as it is — has changed its orientation, creating less drag, slowing the descent.

Please note that the time is still uncertain, though now it’s only +/- 5 hours. Still, that’s a wide swath of Earth in that range, so we’re still not sure where it’ll burn up.

Check the Related posts links below for more info on the satellite, why it’s coming down, and how to read that map. Again, the danger from this is pretty minimal. You may note that the three predictions we’ve had have put re-entry over the ocean or otherwise largely uninhabited areas, and that’s not a coincidence: most of the Earth is like that! That’s why the odds of someone getting hit are so low.

I’m sure we’ll get another update or two in the next few hours, so stay tuned. You can also check the CORDS site for updates, and the NASA page as well.

Related posts:

UARS update 2: new predicted re-entry at 00:58 UTC
Update: satellite *might* fall on Friday at 22:00 UTC +/- 9 hours
NASA satellite due to burn up some time in the next few days

MORE ABOUT: re-entry, satellite, UARS

Comments (40)

  1. speaker2a

    Just 1/2 hour earlier and we might see the show from Colorado!

  2. nancyem

    Someone on your g+ post commented this, and I’d like to echo it: Why specify the 16 minutes, when it’s + / – 5 hours?

  3. jimthompson

    If the error is +/- 5 hours, why can’t it hit ANYWHERE, since the orbital period is less than 90 minutes….

  4. Robin

    A calculation is done to find a value. Then, in science and engineering, it’s standard to than include the uncertainty in that calculation. It involves two different processes: doing the initial calculation and doing an error analysis to determine uncertainty in the calculated or predicted value.

  5. Larry

    Someone explain to me how to calculate 3:16 uTC to EST

  6. jrpowell

    At +1 hour it just about hits Seattle! I’ll be out tonight watching the skies around 9:15pm.

  7. dmbeaster

    Larry – UTC is basically Greenwich time (zero meridian – but not exactly GMT for other reasons), so calculate your local time based on number of time zones away you are from Greenwich. It is the protocol used in many different fields to insure an identical international time standard, and avoid confusion with time zones or daylight savings time alterations. In other words, UTC time is given, and then you make the required adjustment depending on where you are.

  8. dmbeaster

    The blue and yellow lines show all possible locations within the 10 hour window, which is a huge chunk of the globe. So don’t jump on a plane to the Sahara.

  9. Timbo

    If any parts of this satalitte land on land, will nasa try to recover the pieces or would it be finders keeper, loser weeper?

  10. LookedItUp

    3:16 UTC is 11:16 PM EDT.

  11. gmb

    Larry- 11:16 EST (EDT)

  12. nancyem

    The satellite is government property, so NASA has said you can’t have them 😉

  13. Larry: To get Eastern Daylight Saving Time, you subtract 4 hours from UTC. (subtract 5 hours to get Eastern Standard Time)

    Here is a nice conversion table:

  14. WestCoastUS

    Looking at the picture at: shows that +/- 5 hours errors equals an uncertainty of where UARS will come down of about +/- 3 1/2 full earth orbits.

    While South America and China are out of range of the projected path, North America, Europe, the Middle East (!!) and western Asia are all currently still in range, with Africa (somewhere around Chad) at the center of the 9/23 12:02 UTC estimate.

    Nothing to do now but play out the odds that the fragments will not hit anything the U.S. considers important.

  15. Larry

    Thanks fo allyou help on the UTC conversion guys!! Am in Atl, maybe I can see it drift by….

  16. Betta


    03:16 UTC = 03:16 – 4 EDT = 23:16 EDT i.e. 11:16 p.m. EDT

    If you are not using Daylight Savings Time, then it will be 00:16 a.m. EST tomorrow (Saturday, September 24th)

  17. BigBob

    Latest advice from Harro Zimmer
    Report timestamped 19:30 UTC today

    1991-063B (#21701) UARS

    Based on the last five – partially inhomogeneous –
    ELSETs 266.5014… – 266.7449… the fresh decay
    24 September,04:19 UTC +/- 90 minutes
    ascending over 39.55°N, 227.53°E
    (Over the Pacific, on the way to the US West Coast,
    then crossing Canada)

    But I think we will possibly see an additional rev.

    Harro Zimmer Berlin (Germany)


  18. pete

    Impact zone is the Sahara? Why am I seeing a remake of “The Gods Must Be Crazy” ?

  19. Robin B

    Am I reading the chart right and it will be over Valencia, Spain about 7 minutes before the expected re-entry? So, like around 3:09 UTC?

    I’d probably see that as a ground-based observer, right? Brb, setting alarm clock!

  20. Keith Bowden

    You just know there are people running pools on this…

  21. skywatcherz

    whens it coming over the uk & where? please tell me’ somebody.. anybody.

  22. BigBob


    UARS passed south of the UK at about 10:06 pm local time (less than an hour ago). It was in Earth’s shadow. I looked out to see if there was already an plasma glow but nothing seen. Guys in Holland and Norway did the same and saw nothing.

    @ Robin B

    Predictions have moved on from the Sahara. Latest estimates are based on she ditches off the west coast of Canada +- 90 mins. The ground track reaches across the Hudson Bay (see below).

    See this link courtesy of Simone at


  23. Kimi Vaughan

    NASA warns everyone that if they are to find any debris that they think belongs to UARS then you have to call your local police etc etc to report it and you should not touch it as it remains the property of USA!!! Finders are NOT keepers and you could well face a fine etc for keeping parts of the UARS or trying to sell them on ebay etc!!!

  24. WendellFisher

    Jimthomson: It can not hit ANYWHERE on earth even within a plus/minus 5-hour window. That’s because in one orbit (90 minutes or so) it does not pass over the entire earth. A ring that is more-or-less directly below it. Subsequent orbits pass over different places on the earth because the earth is turning under it. So very very very approximately, it would take 12 hours (1/2 an earth rotation) before it had gone over every place on earth to within say a thousand miles or so.

    There is a lot more to it, including especially the angle of the orbit to the equator; I’m only trying to give you a feel for the issue; dont’ take the above too literally.

  25. Number 6

    This all reminds me of some commercials that ran many, many years ago for the GTE corporation (General Telephone & Electronics Corporation) about how they had satellites in space.

    At the time, I rented a small house on a farm, and the only phone service available was from GTE. The service was terrible! I’d be talking to someone and the connection would be dropped…just like w/ some cell phones today. Or, you’d pick up the line and someone would be talking (it was a private line). Or, you’d hear some strangers suddenly talking when you were having a conversation.

    …..So, when the commercials ran regarding GTE’s satellites, for quite a while every time I’d step outside the house or any building, I’d look up to see if one of their creations was crashing to earth and heading toward me. :)

  26. So the current prediction is for just south of the Big Island? Hard to tell how far south from the low res charts. Do I need to make a point of watching the southern sky at 18:16 this afternoon?

  27. walt B.

    I’m in Ca. Hope I get a glimps. I think it will pass to my South.

  28. VinceRN

    By the latest prediction I’ll be able to see it if it’s 15 minutes after the predicted time. Clear skies too, which is odd here. Finger, toes, and eyes crossed. Outside looking NNW or so from a hilltop at after 2100 or so, of course it won’t happen, but it’s getting possibler.

  29. Creekrock

    Ok..i have been doing calculations on the re_entry point, and there is a 70.82% chance it hits water…these calculations were based on hours of research determining the land/water ratio and the realization that nobody knows.

  30. Wzrd1

    TIP Reports for Object 21701, UARS, US
    Report Date/Time 2011-09-23 22:43:00 GMT
    Predicted Decay Time 2011-09-24 04:49:00 GMT +/- 4 Hours
    Predicted Decay Location 2.9° N, 5.5° E
    Direction descending
    Inclination 56.9°
    Revolution Number 10920
    High Interest Object N
    Next Report 2 Hours

    That is from JSpOC.

  31. ceramicfundamentalist

    looks like it will be passing near newfoundland at 11pm, 12:30am, 2am and 3:30am local times. i will definitely be outside looking up, hoping for clear skies.

  32. Wzrd1

    Ceramicfundamentalist, if I looked up tonight, I’d drown. It’s raining pitchforks here in Pennsylvania.
    Hope it stays clear and you get a good view!

  33. Bernie

    It’s 02:05 am British Summer Time now (GMT + 1hr) – anyone know where it is now and if it’ll be visible from the UK in the next few hours?

  34. kurt_eh

    Just watch out for that toilet seat! 😉

  35. Larry

    Any chance I could see this thing before it comes down even as a moving satellite tonight in ga. if so let me know and the direction to look.

    thks for yourhelp

  36. Pete Jackson

    Now they’re saying 0510 GMT +/- 2 hours. Only land areas possible now are Africa, Australia, and Canada.

  37. Starting to look pretty good for eastern Australia, though it would be daylight:

  38. Wzrd1

    JSpOC has different numbers:
    TIP Reports for Object 21701, UARS, US
    Report Date/Time 2011-09-24 01:59:00 GMT
    Predicted Decay Time 2011-09-24 04:16:00 GMT +/- 2 Hours
    Predicted Decay Location 30.9° N, 218.9° E
    Direction ascending
    Inclination 56.9°
    Revolution Number 10921
    High Interest Object Y
    Final Report


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