Space-Track catalog updated today with a note for object 48078, 1996-051Q: "Collided with satellite".This is a new kind of comment entry - haven't seen such a comment for any other satellites before. Let's look a bit closer:
48078 is a small debris object from the Zenit-2 rocket that launched a Tselina-2 electronic spy sat in Sep 1996. Between 1997 and 2021, 8 debris objects were tracked from the rocket. This one, added to the catalog in Mar 2021, has only a single element set, epoch 2021 Mar 16
I conclude that they probably only spotted in tin the data after it collided with something and that's why there's only one set of orbital data. So the collision probably happened shortly after the epoch of the orbit. What did it hit?
The obvious candidate is Yunhai-1-02, which broke up on Mar 18 for unknown reasons. So it will be interesting to compare the orbits of the objects around then
And indeed, a quick analysis of the TLEs show that Yunhai 1-02 (44547) and debris object 1996-051Q (48078) passed within 1 km of each other (so within the uncertainty of the TLEs) at 0741 UTC Mar 18, exactly when 18SPCS reports Yunhai broke up.
37 debris objects (green) have been cataloged so far from the breakup - there are likely to be more. This looks to be the first major confirmed orbital collision in a decade.
Nevertheless it appears that the Yunhai satellite is still under control and able to make orbit adjustments (blue dots) so the collision was not catastrophic?
So where did this debris object come from? The large 9-tonne Zenit second stages in the higher part of LEO have long been identified as a major source of collision risk. But this wasn't the stage itself but a piece that came off it. Let's look at the objects from this 1996 launch
Object A was Kosmos-2333, a Tselina-2 spy sat. Object B is the Zenit rocket stage that put it in orbit. Objects C,D,E,F are small separation motor covers ejected to a higher orbit. Let's look at the remaining debris objects G to Q.
G,H, J, K, L appear to have come off at launch. G and H must be fairly dense and their orbits have not decayed much. J, K and L were light things that have now reentered.
M and M [N?] came off the rocket stage (probably) sometime in 2009. They are decaying at a moderate rate but will be in orbit a few more years.P was cataloged in 2018 but may have been around a lot longer - its orbit is not decaying quickly.
We don't have enough data on object Q to say much about it. (Yeah, ok, make all your jokes about Q being anonymous. Just don't @ me with them.)
But what we can say is there's no evidence that this Zenit rocket stage has broken up. Just small things flaking off it in separate incidents over the years.
Nevertheless, even small things can cause serious damage when they hit your satellite at orbital velocity, as this incident shows.Goodnight!
Oh, one more thing: the Gabbard diagram for the Yunhai debris objects. Most of the objects are in high orbits, but a couple have perigees close to ISS altitude (and some of the rest will eventually decay to that altitude)
Further detail on the Yunhai 1-02 collision: it occurred at 0741:19 UTC 2021 Mar 18, 780 km above Tromso, Norway (at 19.4E 70.9N), at a relative velocity of 13.26 km/s (for the metrically impaired, that's 29660 mph) [red: Yunhai; magenta: debris object 48078]
Orbit of Yunhai was 780 x 785 km x 98.5 deg, in 0716 LTDN sun-synch orbit. Orbit of the debris object was 748 x 939 km x 71.1 deg.
Did the debris do anything to the satellite?
Are there any adverse effects on the satellite?