Updates Tiangong 1 reentry

[Thunder Chicken]

Maybe we should get some robust ceramic card to put into our wallets "Wanderer, should I get killed by space debris, go tell the Orbiter-Forum, I was trying my best to catch it first." :lol:

Mine would say "What were the odds?"

 

[MaverickSawyer]

Maybe we should get some robust ceramic card to put into our wallets "Wanderer, should I get killed by space debris, go tell the Orbiter-Forum, I was trying my best to catch it first." :lol:

"Worth it." :rofl:

 

[Urwumpe]

Some ESA update to the reentry event:

http://blogs.esa.int/rocketscience/2018/01/12/tiangong-1-reentry-updates/

 

[4throck]

"Reentry will take place anywhere between 43ºN and 43ºS (e.g. Spain, France, Portugal, Greece, etc.)"

Funny... I saw Tiangong on one of the first passes right after launch.
And I may see it reenter over my house. Odd coincidence if it happens that way.
:hmm:

 

[cristiapi]

This new reentry map shows 9950 points instead of 3136:

It seems that there is some patterns. Just an artifact?

Here’s the excel data file (964 kB):
http://cristianopi.altervista.org/Tiangong/TIA1-2018-03-02_MC_XLS.7z

 

[GLS]

It may be a little denser in Africa, the East Pacific, North America and Asia.... but there's still too much noise to start shouting "the sky is falling". :lol:

 

[Urwumpe]

There should be some weak hotspots also over places with stronger gravity, so there could really be some patterns. But its still too random.

 

[cristiapi]

I mean that some orbits seems more likely. For example, I see a clear orbit (or ground track) from -180;40 to about -70;-38 which passes over 4 blue dots. There are many patterns like that; I'm the only who see them? %‑)

 

[GLS]

Could the dots be colored by reentry date? That way it maybe be possible so see something more... or just a rainbow :shrug:

 

[cristiapi]

May be I could try to write some lines of VBA, but it's hard for me.
Anyway, the pattern doesn't depend on reentry date. In my understanding it seems that for some orbits there is an higher probability to be the last orbit (before the reentry). In other word, we could know (if what I'm saying is correct) a list of possible reentry locations (the last ground track).
At this time there is much noise, but probably it will vanish in future updates.

 

[Urwumpe]

May be I could try to write some lines of VBA, but it's hard for me.

Maybe its time to use some Python :lol:

 

[cristiapi]

It would be even harder!

 

[Urwumpe]

It would be even harder!

Sure? There are some good libraries around for such calculations, this might make some tasks easier. And there is also at least one good plotting library around.

For example:

https://pypi.python.org/pypi/poliastro

https://github.com/helgee/plyades

https://github.com/python-astrodynamics/astrodynamics

 

[cristiapi]

Sure?

I meant that with Python I can't change the color of the dots in an excel file! :lol:

There are some good libraries around for such calculations, this might make some tasks easier. And there is also at least one good plotting library around.

For example:

https://pypi.python.org/pypi/poliastro

https://github.com/helgee/plyades

https://github.com/python-astrodynamics/astrodynamics

Those libraries are surely interesting, but I already have my C++ libraries to do all the calculations and when I need to use excel, I wrote the data to the excel file directly with my C++ programs.

---------- Post added 04-03-18 at 16:28 ---------- Previous post was 03-03-18 at 21:34 ----------

I did an additional simulation with an improved gravity model: GGM03C (GRACE Gravity Model version 3 Combined):

The old gravity model included only zonal coefficients up to degree 20 (the acceleration doesn’t change with the longitude, but only with the latitude), while this new model includes zonal, tesseral and sectorial coefficients up to degree and order 25. The original GGM03C model is up to degree and order 360, but it’s too slow and I needed to truncate it, but it still retains a good accuracy when compared to the very accurate (and incredibly slow) EGM 2008 model.

There is not much difference with the older simulation, but the reentry date variance is slightly better.

 

[GLS]

In the wee hours of April 5 it flies over Europe... :uhh:

 

[cristiapi]

How do you know?

 

[GLS]

How do you know?

I used the latest TLE in Orbitron and moved time to April 5... I'm sure the (absolute) position it indicates isn't precise, but the orbital plane should be +/- correct... :shrug:

 

[cristiapi]

The osculating plane is almost exact, but we can't say where the Tiangong-1 is at any given time; meanwhile the Earth rotates...

 

[GLS]

The osculating plane is almost exact, but we can't say where the Tiangong-1 is at any given time; meanwhile the Earth rotates...

Yeah, we have to wait for more accuracy on where it will be.

 

[cristiapi]

As expected, the graph for the reentry location is now much clearer:

---------- Post added at 12:18 ---------- Previous post was at 00:46 ----------

The same data but in orthographic projection:

there are many "no-fly zone".