It looks like a planet shield (like the one we can see in Star Trek Beyond).
That’s an interesting idea. Maybe RO’s space battle will be to destroy or somehow open these “gates” to allow the Rogue One team (pluss other troops I’d imagine) to land on the Scariff.
It would make sense to have a shield around Scariff if it’s where they’re constructing the DS, or at least something vital to the DS.