Saturday, 6 August 2022

The flyby of USA 326 by Kosmos 2558 on August 4: a post-analysis

click image to enlarge

In a previous post I discussed the launch of Kosmos 2558 (2022-089A), a Russian military satellite which was launched from Plesetsk on August 1, 2022. 

As I pointed out, it was inserted into the same orbital plane as the American classified military satellite USA 326 (2022-009A, an electro-optical reconnaissance satellite launched in February 2022), at an orbital altitude only a few tens of kilometers below it. 

And that was probably no coincidence: Kosmos 25578 is likely an 'inspector' satellite meant to surreptitiously check out USA 326.


click image to enlarge


The two satellites had a relatively close flyby on August 4. I did a post-encounter analysis based on orbits from before and after the flyby, to assess the time and the distance of the flyby.

I find that the close flyby happened near 14:16:27 UTC (August 4, 2022), give or take a few seconds, at a nominal distance of ~67 km. Most of that distance (about 64 km) is in altitude. 

The flyby happened in daylight near 42.3 N, 25.9 W, over the mid-Atlantic, while both objects were southbound. USA 326 was at an altitude of about 518 km at that time, and Kosdmos 2558 at an altitude of about 453km.

Below is an animation of the flyby, as seen from two viewpoints (first lateral, than oblique):


~67 km is a clear safe distance and therefore no cause for worry (although it worried some generals in the Pentagon perhaps), but nevertheless close enough to make it interesting. I strongly suspect that Kosmos 2558 was imaging USA 326 at the time, in an attempt to gather information on the character of the satellite.

The diagram below gives the distance with time between Kosmos 2558 and USA 326 around the time of the approach.

click diagram to enlarge

It will be interesting to follow the two objects and see whether a new flyby happens at some point. In a previous similar case in early 2020, another Kosmos satellite, Kosmos 2542, was sent to check out the US military satellite USA 245, and released a second satellite, kosmos 2543, that chased the US satellite for a while.


Added comment:

Fred Jansen made a pertinent remark: from launch to operational in a mere 3 days would be awfully fast.
Another issue, brought up by Allan Thomson, is that the Sun-Kosmos 2558-USA 326 angle was quite low during this encounter, which is  not ideal.

However, as the two objecst share the same orbital plane, these encounters repeat at intervals: so even if it was not ready and fully operational yet during this approach, there will be other opportunities in the future. It will be interesting to see whether Kosmos 2558 will raise its orbit at some point, or will do other manoeuvres to keep the precession of its RAAN in line with that of USA 326.

(Note: the orbital elements for USA 326 used in this analysis are based on optical tracking data by an international group of  Independent Space Observers, including myself, Cees Bassa and Russel Eberst)

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