As a chemist, I'd go as far to say as you don't know the exact specifications of [i]dark nebulae[/i] beyond it's physical composition and the addendum of whatever hi-fi you added to isolate your nation. Nebulae, even dense nebulae that are so inappropriately named ([i]dark[/i]), are not immune to radio waves or waves that are beyond the standard spectrum: X-Rays, Gamma, Infrared.

The Graal would have no trouble identifying the presence of thermonuclear heat signatures planetside or the abundance of low frequency radio waves on the planet, this is technology Humanity in the 21st century possess. I won't press the issue however. LOL.