* Inner satellites: These are generally considered to be moons that orbit close to their host planet.
* Diameter of 4800 km: This is a very large size for a moon. The largest moon in our solar system, Ganymede (orbiting Jupiter), has a diameter of 5268 km.
* Not made of dense rock: Moons are typically composed of rock, ice, or a mixture of both. While some moons have significant icy components, it's very uncommon for a moon of that size to be made of something other than dense rock.
It's possible you're thinking of a fictional object or a misunderstanding of some astronomical facts.
