Long duration fireball (Finland, 7.9.2020)

[Timo Kuhmonen]

Observation from 7.9.2020, fireball duration 20+ seconds...
https://www.taivaanvahti.fi/observations/show/93504
https://www.taivaanvahti.fi/observations/show/93529
https://www.taivaanvahti.fi/observations/show/93517

All observations from same event here...
https://www.taivaanvahti.fi/observation ... id/desc/0/

[Mario Braun]

Wow...at first I looked for possible satflares and even ISS transits: Nothing.

This could really be an earth grazer! Esp. with the additional footing showing it near horizon from Tohmajärvi and Tampere 450km away in comparison to the close to zenith footage from Haukipudas.

Edit: Hmm...according to crude calculations with the images from Tampere and Haukipudas, I come to a speed of only about 10km/sec...much too slow for meteors. Maybe space junk?

Greetings, Mario.

[Mario Braun]

Okay...some crude calculations from the limited image data available:

Tampere:
Start: Az.: 355.78° Alt: 3.31°
Distance: 567km Altitude: 32,8km

End: Az.: 20.85° Alt: 3.39°
Distance: 494km Altitude: 29,3km

Haukipudas:
Start: Az: 326.64° Alt: 15.93°
Distance: 190km Altitude: 54,23km

End:Az.: 55.34° Alt: 58.76°
Distance: 138km Altitude: 227,51km

Kiiminki:
Start: Az: 322.07° Alt: 21.64°
Distance: 206km Altitude: 81,73km

End: Az: 40.69° Alt:73.9°
Distance: 126km Altitude: 436,54

226km ground Trajectory, over 26 seconds burn time: 8,7km/s

The data from Tampere is very low over the Horizon and over a large distance, thus may be very skewed due to lens/atmo distortion and the inavailabillity of a lot of reference stars.
However: If I only take Haukipudas and Kiiminki allsky data, the end heights shrink down to a somewhat more plausible range between 120-230km, but this would then lower the velocity of the object further down to something about 7.8km/s.

Greetings Mario.

[Dennis Hennig]

... this would then lower the velocity of the object further down to something about 7.8km/s.
...

A speed which is perfectly consistent with a decaying satellite(-fragment).
So: What was it? I have already passed this question to some satellite observers.

[Mario Braun]

Yes, but the elevated end altitudes would then suggest it bounced back into space. (I did not reverse start and endpoints, checked multiple times now.)

Has something like that ever happened with a piece of spacejunk?

[Timo Kuhmonen]

Okay...some crude calculations from the limited image data available:

hello,

Did you make the analysis, with common known equations, or do you have a specific software or tools ?
I know there is already more precise analysis done here in Finland. That data is currently available to only members of the Finnish fireball group . Generic data is visible at Taivaanvahti...

I did not capture this one with my camera, although it was pointing on right direction. Most probably hidden behind the trees (blocking visibility)...

-Timo

[Mario Braun]

Hello Timo,

I just blundered about getting aproximate trail start and endpoints (Azimuth and Altitude angles) by overlaying the images on a stellarium map of the day from the respective cities in photoshop. Then the rest was just trigonometry on measurements taken with google earth pro.

Greetings, Mario.

[Dennis Hennig]

Yes, but the elevated end altitudes would then suggest it bounced back into space.
(I did not reverse start and endpoints, checked multiple times now.)
Has something like that ever happened with a piece of spacejunk?

Oh yes, You definitely don't wanna sit inside a Soyus/Shenzou/Dragon return capsule bouncing back to space on reentry.
And yes, some years ago there was at least one video around, showing an "earthgrazing" satellite which was supposed to have made back to orbit. For the moment. Anyhow, it should have burnt away in one of the following orbits. As far as I understand, it solely depends on the angle of attack. Flying too steep into the atmosphere, an object rips apart and burns away violently. On the other hand too flat-angle, and the object is "surfing" on the upper atmosphere, and bounces back.

Greetings!

[Dennis Hennig]

Timo, what about the timestamps?
Initially I thought it has to be UT.
But seemingly it is not?

Is it Finlands summer time, UT+4h?

[Timo Kuhmonen]

timestamp that is visible on Taivaanvahti observation title (together with date), that is current local time. Now it is UTC+3h (summertime). If there is timelabel on images, on most cases it is UTC time (not 100% still). This case was seen at 20:03 UTC.

[Dennis Hennig]

Thank You Timo!

[Mario Braun]

Okay, that means my initial calculation is off by an hour. That has some impact about the location of the trail and the distances of the start and endpoints to the viewpoints.
I will do a recalculation later today.

Greetings Mario.

[Mario Braun]

Allright. The data from the proper timepoint of observation yields a way more plausible speed of 15km/s with a groundpath of 400km length. The trail starts at a usual height for meteors of about 52km in the meso/stratosphere, then continues to be seen way up into the exosphere at 640km.

Greetings Mario.