Thermic shelter

Thermic Shelters were a type of shelter which the citizens of Earth were evacuated to before the start of a period of five thousand years of solar flare activity.

However, they were apparently not expected to be capable of sustaining a human population for the whole period, as the government relied on the Ark instead to repopulate the human race. Still, one of the volunteers frozen on the Ark, upon witnessing the situation that existed at the time of his awakening, damned himself for not taking his chances with the shelters. (DW: The Ark in Space)