No one outside the Russian government, and perhaps the Pentagon, knows for sure what Kosmos-2491, -2499, and -2504 are for. But it’s clear enough what the three mystery sats could do, in theory. Zipping across orbital planes hundreds of thousands of feet above Earth, the nimble little spacecraft—which are apparently the size of a mini-refrigerator—are able to get really close to other satellites. Close as in a few dozen feet away.
And if they can get that close, the little robots could spy on, hijack, and even destroy other sats.
In other words, Kosmos-2491 and its triplets might be space weapons, the likes of which few other nations possess. And if so, they could upset the orbital balance of power, at a time when government agencies, armies, scientists, and everyday people—in the United States, especially—depend on satellites for communications, surveillance, science, and navigation.