A triumphant return for the seven astronauts
The astronauts on Columbia gave the space telescope new solar wings, a better central power unit and the most advanced optical camera ever put in orbit.
They also installed an experimental refrigeration system that should allow astronomers to revive a disabled infrared camera.
The Hubble Space Telescope (HST) has already made astonishing discoveries about the nature and age of the Universe. The latest upgrade - the third big refurbishment in its 12-year history - should lead scientists to even more remarkable insights.
Back up
The shuttle landed right on time on the five-kilometre-long (three miles) runway, illuminated by powerful xenon floodlights.
"Field in sight on a beautiful night," radioed Commander Scott Altman, moments before the touchdown at 04:32 EST (09:32 GMT).
All the systems upgraded on the HST, which orbits more than 560 kilometres (350 miles) above the Earth were performing well, said the American space agency (Nasa).
Cooling problem
There is great excitement about what the new Advanced Camera for Surveys could achieve. It should give a tenfold improvement in Hubble's "eyesight", allowing astronomers to look as far back as the first billion years of the universe.
Astronaut-astrophysicist John Grunsfeld said Hubble easily should make it to 2010, at which time Nasa intends to decommission the observatory and bring it back for museum display. One more servicing mission is planned, in 2004.
Engineers will want to closely scrutinize Columbia. A problem detected in the oldest space shuttle's cooling system shortly after launch nearly led to the mission being scrapped.
Nasa said it was probable that debris got stuck inside the system during the orbiter's recent overhaul.