Series Alpha sensor probe

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 a 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)