The mission was almost abandoned when they found a problem with the shuttle's vital cooling system.
But now Hubble's anchored, the crew can fix and update some of the of its old instruments.
As they secured the craft, astronaut John Grunsfeld - who's worked on Hubble before - said: "It's great to see an old friend".
The spacemen are now looking forward to five days of space-walking.
They'll certainly be getting a stunning view up there!