[amsat-bb] Tiangong Re-entry (0000 UTC +/- 2.5 hrs)

[Greg D]

I just updated the keps on gPredict, and Tiangong-1 disappeared from the
list.  Where'd it come down, or are rumors of its demise ever so
slightly exaggerated?  Heavens-above still thinks it's up there.

Greg  KO6TH


Robert Bruninga wrote:
> Since this is journalism, I think you and some others are right.  If one
> simply looks at latitude as a number, then the latitude near the
> inclination will have a higher probability of appearing.  But the best
> feedback came from Ralph W0RPK who pointed out this page which is tracking
> the orbit with updated predictions:
> http://www.aerospace.org/CORDSuploads/TiangongStoryboard.png
>
> And the USA is about as far as you can get from the predicted impact.  The
> USA is 12 hours out of cycle with the orbit.
>
> The prediction there is currently showing about 0000 UTC which is 8 PM EDT
> plus or minus 2.5 hours. (which is about 3 orbits worth).  And although
> those orbits cover a vast Pacific and Atlantic oceans, a good portion of
> them cross the middle east through Russia and china.
>
> Bob, WB4APR
>
> On Sun, Apr 1, 2018 at 11:26 AM, Gary Bender, WS5N <ws5n at wildblue.net>
> wrote:
>
>> I was thinking the favoring of higher latitudes for reentry was because
>> the apparent sine wave of the ground track naturally slows down in
>> "latitude velocity" as it peaks at 43 degrees and reverses.  Add in the
>> rotation of the earth under it and you end up with a bit more dwell time
>> above 38 degrees.  It is changing latitude much faster between the
>> extremes.  (Or maybe I am over thinking it.)
>>  --
>>     Gary, WS5N
>>
>> ----- Original Message -----
>> From: "Robert Bruninga" <bruninga at usna.edu>
>> To: "amsat bb" <amsat-bb at amsat.org>
>> Cc: "TAPR APRS Mailing List" <aprssig at tapr.org>
>> Sent: Saturday, March 31, 2018 5:55:17 PM
>> Subject: Re: [aprssig] [amsat-bb] Tiangong Re-entry on Heavens bove
>>
>>> Hi Bob, do you know the object number by chance?
>> No, but this link shows that the higher probabilities or re-entry are
>> between about 38 to 43 degree latitudes north and south.
>>
>> https://www.theguardian.com/science/2018/mar/30/chinas-tiangong-1-space-st
>> ation-will-crash-to-earth-this-weekend
>> <https://www.theguardian.com/science/2018/mar/30/chinas-tiangong-1-space-st%0Aation-will-crash-to-earth-this-weekend>
>>
>> Im not sure why those would be slightly higher.  43 degrees is its maximum
>> excursion (matches its inclination)...  Maybe its because as it passes
>> over the equatorial bulge, it sees the higher drag and that will start the
>> demise which will occur then 20 minutes later?
>>
>> Bob
>> -----Original Message-----
>> From: Robert Bruninga
>> Sent: Saturday, March 31, 2018 9:16 AM
>> Subject: [amsat-bb] Tiangong Re-enetry on Heavens bove
>>
>> You can see the live track of Taengong to re-enter in the next 24 hours on
>> http://www.heavens-above.com/
>>
>> Just remember, as it suffers increased drag, it will speed up and be ahead
>> of classic predictions.
>>
>> But at least you can see when you are under the orbit as to whether it is
>> worth going outside.  I 'd go out several minutes before the prediction
>> since we dont know how quickly they are updating the elements as it speeds
>> up.
>>
>> and even if it is daytime, you will see it if it comes in in your area...
>>
>> Bob
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