ICBM launch detection has been done since the 60s with satellites using infrared sensors to detect the heat emitted by the rocket engine. https://en.wikipedia.

ICBM launch detection has been done since the 60s with satellites using infrared sensors to detect the heat emitted by the rocket engine. https://en.wikipedia.org/wiki/Defense_Support_Program https://en.wikipedia.org/wiki/Defense_Support_Program https://en.wikipedia.org/wiki/Space-Based_Infrared_System https://en.wikipedia.org/wiki/Space-Based_Infrared_System