Short answers, pulled from the story.
Serpukhov-15 is a military townlet near Kurilovo in Kaluga Oblast, Russia, that serves as the western control centre for Russia's Oko early warning satellites. It monitors for ballistic missile launches, primarily from the continental United States, and feeds processed data to the Russian Aerospace Defence Forces centre in Solnechnogorsk.
On the 26th of September 1983, the Oko satellite system at Serpukhov-15 erroneously detected the launch of five Minuteman ICBMs from the United States. Lieutenant Colonel Stanislav Petrov, the officer on duty, discounted the alert because early warning radar did not corroborate it and because the system had only recently become operational. The malfunction was later attributed to high clouds and autumn equinox conditions.
Stanislav Petrov was a Lieutenant Colonel on duty at Serpukhov-15 on the 26th of September 1983. When the Oko system falsely reported five incoming Minuteman missiles, he decided not to treat the alert as genuine because early warning radar showed nothing and the system had only recently become operational.
A fire on the 10th of May 2001 cut communications between the control centre and its four US-K satellites for 12 hours. Because molniya-orbit satellites require ground contact every two or three orbits to maintain position, the outage caused the immediate loss of Kosmos 2340 and Kosmos 2351, and contributed to the loss of Kosmos 2368 and Kosmos 2342 within a year.
A total of 101 satellites were launched under the Oko programme, spanning two generations: the US-K satellites in highly elliptical molniya orbits and the US-KMO satellites in geosynchronous orbit. The last US-KMO satellite, Kosmos 2479, launched on the 30th of March 2012.
The Oko satellites are due to be replaced by a new system called EKS. The final US-K satellite, Kosmos 2469, launched on the 30th of September 2010, and the last US-KMO satellite, Kosmos 2479, launched on the 30th of March 2012, marking the end of new Oko launches.