Astronauts are getting ready to launch into space on the shuttle Atlantis for one of their most dangerous missions yet - fixing the Hubble telescope. Ricky's been finding out more.
The giant telescope has been in orbit, taking pictures of space for almost 20 years and is badly in need of repair.
During five long spacewalks, astronauts will repair and replace broken parts and install powerful new cameras.
The mission's considered really risky as the telescope is a long way from the International Space Station.