Like the knees of many other middle-aged workers, the joints of the enormous Mars Antenna need replacing. The giant radio dish is a crucial element of NASA's Deep Space Network, and has worked tirelessly at its location in Goldstone, Calif., for over 40 years.

This historic antenna, which measures 230 feet in diameter (70 meters) and communicates with deep space missions, once received Neil Armstrong's famous Apollo 11 message: "That's one small step for man; one giant leap for mankind."

Now, this laborer needs replacement of a portion of its hydrostatic bearing assembly, the system that enables the antenna to rotate horizontally. The repair will be no mean feat: It involves lifting 9 million lbs (4 million kg) of delicate scientific equipment 0.2 inches (5 mm), in order to allow the replacement of the steel runner, walls and supporting grout, which has never been done before.

http://www.space.com/news/deep-space-antenna-fix-100310.html