The cryogenic chamber was a facility aboard Nerva Beacon where humans were held in suspended animation. A Wirrn Queen boarded Nerva and laid an egg in one of the humans, Dune, who was eaten as they hatched.
In 16087, the Fourth Doctor and Harry Sullivan found Sarah Jane Smith in the cryogenic chamber, having undergone tissue irradiation inadvertently. First Medtech Vira was woken and assisted the pair in the revivification of Sarah. She then woke Lazar, or Noah as he was nicknamed, the commander. An intervals, Libri, Rogin and Lycett were also revivified.
Noah became infected by the Wirrn and underwent metamorphosis, becoming their Swarm Leader. The Wirrn planned to absorb the humans still in the cryogenic chmaber in suspended animation to assimilate their knowledge of advanced technology into the collective memory of their species.
Sarah took a power cable from Nerva's transport ship through the service conduits which the Doctor used this to keep the Wirrn at bay, taking advantage of their susceptibility to electricity. The sleepers' survival was assured when Noah destroyed the other Wirrn. In parting, Vira told the Doctor she would soon wake the other humans in the chamber. (TV: The Ark in Space)