Working a mission for 3 rebel data trans. Go to system and first thing I notice is signal sources not showing on my Nav screen. Shows everything else in system but not signals (unidentified, weak, strong...etc). Even when I'm looking right at them they do not show on nav screen. I was seeing something about scanning nav beacons, so I got as close to one as possible (I do not have a discovery scanner or detailed surface scanner) nothing. What has changed. I would normally fly around slow while looking at my nav panel and as soon as a weak signal source showed up I would lock on it. Do they still have weak signal source? Found a few unidentified signals visually but not weak.