Sputnik
Sputnik was the name of Earth's first artificial satellite. It was launched by the Soviet Union in October 1957. Its launch was reported by the BBC on 15 October of that year (AUDIO: Unregenerate!) and the marked the point in which Earth became a Level 5 civilisation. (PROSE: Time Traveller's Diary)
The satellite was described by Susan Foreman as "just a small ball", which, as John Brent quickly pointed out, was also mirrored. This helped conspiracy theorists believe that the Russians were freezing England through a freezing ray sent from Sputnik, whose mirrors would make it easier to reflect the ray down to Earth. This theory was known as the Novosibirsk Project. (PROSE: Time and Relative)
An earlier satellite with the same name was secretly launched on 1 May of that year, but it was hijacked by the Master. The Soviets covered up the existence of the satellite. (PROSE: The First Frontier)
Following the launch of Sputnik 1, the Shadow Proclamation reclassified Earth as a Class 5 civilisation. (PROSE: Time Traveller's Diary)