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| Object C (click image to enlarge) |
Kosmos 2558 (2022-089A, cat nr. 53323) is a Russian military satellite that was launched from Plesetsk three years ago, on 1 August 2022. It was launched into the orbital plane of an American ADVANCED CRYSTAL spy satellite, USA 326. It is therefore believed to be a 'Nivelir' type 'inspection satellite' (see also this earlier discussion of several of such missions, and Bart Hendrickx' Space Review article on the Nivelir program here).
As I recently wrote, there have now been four of these missions in a five-year timespan. Apart from Kosmos 2558 discussed here, these are: Kosmos 2542/2543 launched in the orbital plane of USA 245 in 2020; Kosmos 2576 placed in the orbital plane of USA 314 in 2024 (see this earlier blogpost); and very recently, Kosmos 2588 placed in the orbital plane of USA 338 (see this earlier blogpost).
With the exception of Kosmos 2542/2543, which have been deorbitted, all three remaining missions are still dedicatedly shadowing their American targets, keeping their orbital altitude and inclination difference such that the rate of RAAN (node) precession matches that of their target. This ensures that the orbital planes do not drift apart.
While mostly seen as 'inspection missions', I have repeatedly voiced a concern that these missions might be the positioning of 'dormant' on-orbit Anti-Satellite (ASAT) weapons. To me, the long, ongoing shadowing of what are some of the most prized US military space assets, their KH-11 Advanced Enhanced Crystal high-resolution optical IMINT satellites, is odd for 'just' an inspection mission. What is there still left to inspect after 3+ years? The satellites make only periodic close approaches (every few days) so monitoring of attitude (pointing) or radio signals is not an explanation.
Understandibly, the 'stalking' behaviour of these Kosmos satellites on their satellites makes the US military nervous. And now they have yet another reason to get even more nervous: on 26 June 2025 near 12:03 UTC (according to my analysis), Kosmos 2558 released a second object, currently designated as 'Object C' (2022-089C, cat nr. 64627).
The release is actually visible in the orbital elements for kosmos 2558, as a sudden slight lowering of the orbit:
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| Click diagram to enlarge |
This is the third time we see this kind of 'Matrushka Doll' behaviour from Russian military satellites in five years time.
Shortly after reaching orbit in 2020, Kosmos 2542 released a sub-satellite too, Kosmos 2543, which next in turn fired what is interpreted as a projectile, 'object E' (the latter was widely seen as an ASAT technology test at the time).
In addition, more recently, Kosmos 2583 released an object, 'Object F' (2025-026F), on 18 March this year, as part of a complex series of RPO's (Rendezvous- and Proximity Operations) between Kosmos 2581, Kosmos 2582, Kosmos 2583 and said 'Object F'. I will publish a separate blogpost on these later [edit: separate post now available here].
In 2020 and more recently with Kosmos 2583 and 'Object F', this spawning of other objects happened within weeks after the launch of the parent satellite. But this time with Kosmos 2558 and 'Object C', the release of a second object happened almost three years after launch.
I observed Kosmos 2558 and the newly released 'Object C' last night. 'Object C' reached magnitude +8. The images below are 1-second frame stacks from video observations I made from Leiden, the Netherlands, on the night of 28-29 June 2025, two-and-a-half days after 'Object C' was released. At the time of observation, 'Object C' was some 143 km distant from Kosmos 2558, passing the camera FOV some 16-seconds after it. The first framestack shows 'Object C'; the second shows Kosmos 2558.
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| Object C (click image to enlarge) |
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| Kosmos 2558 (click image to enlarge) |
Below is the video footage of the pass in question. The first to pass through the FOV is Kosmos 2558 as a bright object: then, some 16 seconds later, 'Object C' passes through the FOV as a fainter object. The footage was shot from Leiden, the Netherlands, with a WATEC 902H2 Supreme camera and Samyang 1.2/85 mm lens.
It will be interesting to see whether any manoeuvering between the two objects is happening over the coming weeks.
UPDATE 4 July 2025:
Since release, Object C has been manouevering with respect to Kosmos 2558. While initially manouevering back to Kosmos 2558, it lowered its orbit significantly (by 15 km) on July 3 near 18:42 UTC. See diagram below.
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| Click diagram to enlarge |
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