Shortly after midnight, the bunker’s computers reported that one intercontinental ballistic missile was heading toward the Soviet Union from the United States. Petrov considered the detection a computer error, since a first-strike nuclear attack by the United States was likely to involve hundreds of simultaneous missile launches in order to disable any Soviet means of a counterattack. Furthermore, the satellite system’s reliability had been questioned in the past.[12] Petrov dismissed the warning as a false alarm, though accounts of the event differ as to whether he notified his superiors[11] or not[8] after he concluded that the computer detections were false and that no missile had been launched. Petrov’s suspicion that the warning system was malfunctioning was confirmed when no missile in fact arrived. Later, the computers identified four additional missiles in the air, all directed towards the Soviet Union. Petrov suspected that the computer system was malfunctioning again, despite having no direct means to confirm this.[13] The Soviet Union’s land radar was incapable of detecting missiles beyond the horizon.[12]
The initial detection was one missile. Petrov dismissed this as a false alarm. Later four more missiles were detected, and Petrov also dismissed this as a false alarm. Other accounts combine both sub-incidents together and say that five missiles were detected.
I choose to focus on the first detection because that’s when Petrov made the critical decision, in my mind, to not trust the satellite early warning network. The second detection of four missiles isn’t as important to me, because at that point Petrov has already chosen to disregard warnings from the satellite network.
It seems like the official story as you for example find it on Wikipedia says that the system detected five ICBMs.
From https://en.wikipedia.org/wiki/1983_Soviet_nuclear_false_alarm_incident:
The initial detection was one missile. Petrov dismissed this as a false alarm. Later four more missiles were detected, and Petrov also dismissed this as a false alarm. Other accounts combine both sub-incidents together and say that five missiles were detected.
I choose to focus on the first detection because that’s when Petrov made the critical decision, in my mind, to not trust the satellite early warning network. The second detection of four missiles isn’t as important to me, because at that point Petrov has already chosen to disregard warnings from the satellite network.