During scheduled world map activities like raids, VXP weekend, or Bounty there are world map targets available. These targets are on a rotating spawn timer, and will usually appear every 15 to 30 minutes around the world map. Some targets will only spawn around Nav Relay Towers or near Sub-Sector Resource Bases. Check around those areas if you don't see them directly near your base.
Some targets may be removed from the world map after a set amount of time (to remove old or partially damaged targets) to make room for fresh ones. If you don't see any targets or notice them disappearing, wait a few minutes and they should be available again soon.