It had six modules, arranged "like a string of sausages", according to the Fourth Doctor. The control room was in the front, followed by the science module, the dorms, the living quarters, the greenhouse, and the hold, which housed Chang Hu's secret monitoring equipment. The six astronauts' actions were record on camera and sent back to Earth by encrypted transmissions as entertainment to raise funds for space missions.
When the Doctor and Sarah Jane Smith visited the spacecraft, Barrett had discovered the cameras and assumed the mission was a fake. He opened the airlock to prove it, but was blown out into space. (PROSE: Observer Effect)