A Series Alpha sensor probe is a type of automated probe used by Starfleet in the 23rd century. They were designed to investigate spatial areas considered too hazardous for exploration by starships, and employed heavy shielding from powerful radiation.

In 2265, Professor Lindsey Cameron modified a group of six of Series Alpha sensor probes to create a "moving shield" intended to protect the planet Mestiko from the damaging radiation from a rogue pulsar passing through the Mestiko system. Unfortunately, one of the six probes malfunctioned, leading to disastrous results for Mestiko. (TOS eBook: Mere Anarchy: Things Fall Apart)