Kosmos 520 (Russian: Космос 520 meaning Cosmos 520) was the first Soviet US-K missile early warning satellite.

The satellite is designed to identify missile launches using optical telescopes and infrared sensors.

[2] Kosmos 520 was launched from Site 41/1 at Plesetsk Cosmodrome in the Soviet Union.

[2][5] A Molniya-M carrier rocket with a 2BL upper stage was used to perform the launch, which took place at 19:19 UTC on 19 September 1972.

[3] The United States Space Command assigned it the Satellite Catalog Number 06192.