Early on, defenseless.
I will usually lose a couple of geosurvey ships. As tech improves, they pickup armor, speed, and passives. I usually drop a CIWS on them as well, along with good passives.
The last couple of games, I have a dedicated scout go through with BIG sensors and sweep the system. If its clean, the scout moves on, and the dedicated surveyors come through. Works well, and saves me some ships. A bit more micromanaging, and I still lose the odd geosurvey ship, but meh, they are cheap.