Orbital data suggest that as of the end of 2025 Russia may have only one functioning early-warning satellite of the Tundra type. This is a significant decline from the situation in March 2025, when three satellites of the constellation - Cosmos-2541 (launched in September 2019), Cosmos-2552 (November 2021), and Cosmos-2563 (November 2022) - appeared to be operational.

Now it appears that for Cosmos-2541, the orbit correction maneuver successfully conducted in March 2025 was the last one. Another satellite of those three, Cosmos-2563, appears to have failed at some point after the last successful maneuver in July 2025. Images below show the changes in mean motion that testify to the failures.

The only satellite that doesn't show clear signs of failure is Cosmos-2552, launched in November 2021. However, based on recent patterns, it should have performed an orbit correction sometime in November 2025 (see the main image in the post). But it is too early to say that Cosmos-2552 has ended its operations.

I should note again that the apparent loss of early-warning satellites is not necessarily a cause for alarm. Russia does not rely on the space-based segment of its early-warning system to the extent the United States does. For a discussion, see this 2015 post or my Science & Global Security article.