Sarath

Sarath was a planet in the same system as Mirath, once visited by the First Doctor, Susan Foreman, Ian Chesterton and Barbara Wright. The inhabitants were humans who didn't realise that they had travelled through space before because of a hazy history. The planet was soon to be destroyed by pieces of the Sarath moon breaking up and crashing to the surface after a meteor struck it. By the time the TARDIS arrived on the planet, a decade after the moon was struck, the city of Arkhaven was apparently the last surviving suitably advanced city, protected due to it being in a geologically stable area with a self-contained economy. They were building a rocket to try and escape the devastation to travel to the neighbouring planet of Mirath, with the Doctor's aid allowing a last desperate plan to save the six hundred or so final survivors of Arkhaven to depart for Mirath in relative safety. (PROSE:  City at World's End)