Missile flight times and warnings

[adimar]

Originally Posted by Silent Hunter UK

The US would be able to track them however; their orbital surveillance is far better than the USSR's ever was.

The us would absolutely track them , but warning time would only be approx 2 minutes. And this assumes they wouldn't maneuver.
I very much doubt (though have no information to disprove) that tracking was continuous. It is far more likely orbit would be calculated with periodic checks.
If object-X a soviet "weather satellite" would not appear in it's expected trajectory. I don't think it will trigger a preemptive strike by the us even if it was known to be a pre-launched weapon. Thus leaving the us open to surprise attack.

Adi