US-A and US-P Russian military satellites

They sound like United States military satellites. But these are Soviet electronic intelligence satellites for ocean surveillance, and targeting and guidance for the Soviet Navy's cruise missiles. The first subsystem included a network of the satellites designated US-P, which would intercept radio-signals emitted by enemy ships. The US stands for "Upravlayemyi Sputnik" (Controlled Satellite). Letter "P" meant "passivniy" (passive) as opposed to the second subsystem of the network: US-A or "aktivniy" (active). The US-A satellites would use radar to locate ships which maintained "radio-silence" and therefore remained invisible to the US-A satellites.

The high power consumption of the active radar required a nuclear reactor as power source. The satellites were known as RORSAT in the West. The passive detection systems did not need as much power, so it was fitted with solar arrays.

More Information

Gunter's Space Page: US-A
Gunter's Space Page: US-P
Russian Space Web