There is a light in the bottom right corner of your scope view tdc/torp setting console. When it's lit up it's operating on 'memory', so to speak - meaning you sent it a course and speed of the target and it still predicts position based on those qualities. When it's off it's ready for fresh info - you lock onto the target and it'll update. If you click the light again, it'll track from those settings whether you're looking through the scope or the scope is down.
I once popped up the scope and 'locked' on a target, thinking the data refreshed but unfortunately I didn't disengage the light/old data tracking. The old data was tracking a different freighter. So instead of two hits apiece, the first frieghter was hit with 4. Argh.