Minerals bonus is halved for bases without Aerospace Complexes, and can not in any event exceed the size of the base.
This improvement is a mining operation on one of Planet's moons, raining down mineral wealth on all of your faction's bases. The wonderful thing about the Nessus Mining Station is that it's clean minerals.....it doesn't increase your base's ecological damage.
As with all orbital improvements, there's no reason to have more Nessus Stations than the population of your largest base at any given time. At that point, your faction is saturated with mineral wealth.
