SPOILERS->urk wrote: That would be my wild, unsupported guess. We know the Halo Array is a weapon and it uses seven halos placed about the galaxy and a central Ark as a control point. The 719MHz image and the accompanying glyphs that match show eight orbits with a central control, a departure from the previous glyphs' design.
There has been plenty of speculation about the Halo Array being used as a "seeder" of sorts. We know that somehow, after the last firing, certain species emerged. Since our knowledge of evolution refutes the notion that they went from small organic life, incapable of sustaining the Flood to sentient beings with sufficient mass in 100,000 years, we have to entertain other possibilities.
And since this image is very clearly depicting the Ark, and since we know that the Halo Array differs to such a degree that it cannot be said to be one in the same, we can speculate that this is a new system, or at least another facet of the system. Whether or not it is a "shield" as I have suggested, is rampant speculation, but speculation that seems to fit with what we know.
It could be both shield and weapon. In Ghosts of Onyx, that is kind of how the planet Onyx planet is described. I forget the exact wording, but there is a point where Dr. Halsey interprets some Forerunner text and it references Onyx as "sword and shield". This is later demonstrated as some of the characters hide inside the planet (Are protected), while the entire of the surface blasts away and it's revealed that the surface is made out of trillions of interlocked sentinels. The description of the portal to the interior of Onyx is quite similar to what we've seen of the (alleged) Halo 3 Ark structure (i.e. a circular opening with radial arms that hinge to open/close, and a bright, golden light in the very center).
Anyway, what I'm getting at is that the 719Hz glyph seems to be a reference to these types of formations, and these types of formations seem to be associated with some sort of root level Halo control and/or shelter from Halo firings.