Space Station W3, also known as the Wheel, was a space station located in the Sol system in the 21st century. Its mission was to warn spacecraft of meteorite storms, monitor stellar activity, and conduct scientific research. It was armed with an x-ray laser and a force field.
Two Cybermen invaded the station, intending to use it as a beacon for their invasion fleet. The Doctor freed the crew from the Cybermen's hypnotic control and destroyed their fleet. (DW: The Wheel in Space)