The IR systems are space-based and look for rocket plumes in the ascent phase. Once a rocket gets above the troposphere there's no clouds to obscure it. It's an

The IR systems are space-based and look for rocket plumes in the ascent phase. Once a rocket gets above the troposphere there's no clouds to obscure it. It's an intensely bright IR source that easily stands out from the -60°C surrounding atmosphere. Just a second of observing the plume's trajectory will tell the difference between and orbital or ballistic one. Ballistic missiles will also be launched over the poles to travel the shortest distance to their targets. So IR plumes over the North Pole either means Santa's upped his present delivery game or there's an incoming ballistic missile attack.