Kukulkan's probe

From Memory Alpha, the free Star Trek reference

Kukulkan's probe was an automated spacecraft that was sent out by Kukulkan in 2270. It approached the Federation home worlds, made a scan of Earth system, and then signaled out into space. Before it could be intercepted, it self-destructed. The USS Enterprise followed the trail of disrupted matter left by the probe's highly advanced propulsion system. (TAS: "How Sharper Than a Serpent's Tooth")