Probe ships were a type of spacecraft used by the Morestrans. Controller Salamar captained a probe ship that travelled to Zeta Minor to make contact with Professor Sorenson's expedition, who had not been heard from since their arrival on the planet.
When the craft attempted to take off, the cyclostimulators failed due to the anti-matter minerals on board. The anti-matter creature attacked, killing several crew members. On the Doctor's advice, the force field was linked to the atomic accelerator, repelling the creature.
Most of the minerals were removed, but Sorenson secreted some. The ship managed to take off, but found itself stuck in the planet's gravitational pull and starting to accelerate back towards the surface. Infected by anti-matter, Sorenson killed Morelli and De Haan. The Doctor and Sarah were blamed and Salamar ordered for their ejection through the facilities provided on ship for the removal of deceased crew.
After Reig was killed, Vishinsky assumed command, declaring Salamar unfit. The deposed Controller attacked Sorenson with a neutron accelerator, creating pure anti-matter duplicates that began moving about the ship killing the crew.
The Doctor and Sarah were spared execution and the former used the TARDIS to taken Sorenson and the remaining minerals back to Zeta Minor where they were returned to the creature. The duplicates vanished, Sorenson was returned to his former self and the probe ship escaped. Vishinsky explained that, after they had travelled far enough, they would be met and provided with an emergency refuelling. (TV: Planet of Evil)