US-A

US-A

US-A (Upravlenniye Sputnik Aktivny) were active radar satellites for ocean surveilance. The high power consumtion of the active radar required a nuclear reactor as power source. The satellites were known as RORSAT in the west.

At the end of the mission, the reactor compartment is separated and boosted ito a higher storage orbit. Beginning with Kosmos 1176, the reactor core was also ejected to avoid radioactive material reaching the ground in the event of reentry.

In 1973, an US-A satellite failed to reach orbit and burned up. Two missions failed to boost their reactor into the safe orbit. Kosmos 954's reactor reentered over Canada and polluted an area of 124000 m². Kosmos 1402 ejected the reactor core before reentry. The unprotected core burned up over the south Atlantic.