You obtain this trophy by scanning all necessary species on 7 planets.
The list of fauna necessary is presented in the middle of the dashboard for each planet.
The species will be ticked up as you scan them.
A message will show in the bottom right corner of your screen when you scan a new species.
If this species was in the required list, the message will remind you how many are left to be scanned to get to 100 %.
There used to be an exploit whereby you could upload a 100% score on an empty planet.
This has been patched up, and the button does not show on the screen anymore.