Factorio Forums

Note** needs further testing!! sorry didnt screen shot.
Note(1)* do alians dislike/agro radar scans (able to sense radar waves etc.)

not system related what a radar looks at a spot containing alians i think the alians are able to see you for a split second and come after you. i have minimal pollution(5X5) alians are at least 8 squares away from edge of pollution and i got attacked first time in the game(50+ days in-game) first time using radar as well and not long after i got attacked, went for radar first(1) so i cut power to my radars and they stopped then i checked mini map and it had just finished scanning an alian patch (small one or i would have died thank god)

after taking down radar i have not been attacked while making this post.

after researching armor and guns i did further testing and the radar did not draw attention this time while scanning more alians. still do not know the cause for the attack -.-

Could it be so: radar needs power, power production causes more pollution, biters will come. Take down radar, no electric demand, lower pollution, biter stay.

I'm not entirely sure, but here is what I think happens -
The radar counts as a military building, so biters agro it when close by, regardless of pollution (Same way they attack turrets even do they cause no pollution).
So what I assume happens is - a group of biters wanders off to make a new base, and walk close to the radar. When they get close enough to see it they agro on it, as it is considered a military building. Once agro they will pursue to attack your base, even if outside of pollution range.

This makes sense to me, and is consistent with the behavior I have been witnessing.