There was the fact that direct radio communication with the Earth, around the curve of the Moon, was impossible-the Tovies didn't like radio-relay orbiters, useful for beamed, short-wave messages.
"The Planet Strappers"
Raymond Zinke Gallun
Or, rather, the string of orbiters and artificial satellites around Niflheim.
"Uller Uprising"
Henry Beam Piper, John D. Clark and John F. Carr