Across the Sea of Suns.

'''Benford, Gregory. Across the Sea of Suns.''' New York: Timescape-Simon, 1984.

To prevent the evolution of "sophisticated organic civilizations" a "machine culture" leaves weapons satellites in orbit around once promising planets. By the end of the novel, Earth has such a "'watcher.'" Rev. Jerry L. Parsons, FR #65 (March 1984): 25, source for this entry, and quote.