SF short story, maybe "House by the Side of the Road"? Human at remote interstellar site as first defense line against alien invasion, probably 1970s.
This isn't about a defense station in interstellar space. I am going primarily by the suggested publication date and the misremembered title, which sounded like something Simak might make up.
"Of course not," said Tyler. "Pluto never was a planet."
Instead, three astronauts are sent on a remote probe to Pluto and find an alien artifact.
The artifact is Pluto itself, a giant dust-covered hollow metal sphere. The explorers find a set of construction plans for the solar system.
But apparently things haven't turned out to plan.
Organic Marble mentioned Keith Laumer as a possibility. Laumer wrote a story that appeared in the April 1967 issue of Galaxy called 'Thunderhead'. Earth is at war with a spider-like race called the Djann. 20 years before the story opens, Lt. Carnaby had been dropped on an isolated Rim world to man a one-person sensor station. Unknown to him, the ship that set up the station was destroyed and the military authorities have forgotten it even exists. For years the Terran fleet has blockaded the Djann home system, but a Djann ship filled with eggs has pieced the blockade and is headed into the galaxy to set up shop somewhere else. Carnaby lures the ship to his planet with a phony Djann distress signal and then must face its crew alone...