Why is the Pine Gap defence facility attracting new protests?

Hundreds of protesters have gathered this week at Pine Gap in the Northern Territory, calling for the defence facility to be shut down. They're concerned about the expansion of the secretive base. Pine Gap is about 18 kilometres south-west of Alice Springs and while it was originally sold to the public as a space base, the joint Australian-US facility has since expanded to become a major intelligence and surveillance facility. Its mission and secrecy have made it the target of countless protests.