Commander Scott Altman, a veteran of three previous spaceflights, was first aboard.
He was followed by rookie astronaut Andrew Feustel, 43, and the rest of the crew: pilot Greg Johnson, 54, flight engineer Megan McArthur, 37, lead spacewalker John Grunsfeld, 50, and astronauts Michael Massimino and Michael Good, both 46.
Meteorologists predicted a 90 percent chance the weather would be suitable for liftoff, although there was a slight concern about low clouds at the shuttle's emergency landing site in Spain.
The astronauts plan to spend 11 days in orbit on a final mission to service the Hubble telescope.
NASA has dispatched space shuttle crews to repair and upgrade Hubble four times since it was put into orbit in 1990.
But Atlantis' mission is the first since the 2003 Columbia accident, which changed the way NASA did business.
Among its post-Columbia safety improvements, NASA set up the International Space Station as an emergency shelter for shuttle astronauts whose spaceship may be too damaged to attempt the return flight through Earth's atmosphere.
But Atlantis is heading toward an orbit too far to reach the outpost, so NASA has a second shuttle poised at the launch site ready to mount an emergency rescue mission if needed.
The 2003 accident also delayed the fifth house call to Hubble, leaving the observatory with its main camera sidelined by an electronics problem, two other instruments shut down, no backups for a key computer or the positioning system, and 20-year-old batteries that can only be half charged.
"On this mission, we're going for broke," said Hubble project scientist David Leckrone. "We set the bar extraordinarily high for ourselves."
During five spacewalks, astronauts plan to install two new cameras, repair two of the broken instruments, replace all six positioning gyroscopes and batteries, shore up the telescope's thermal insulation and attach a docking ring so that Hubble can be removed from orbit upon completion of its mission.
NASA hopes that with the upgrades Hubble, which has cost about $10 billion so far, will last until at least 2014, at which time its replacement should be in orbit and operational.
Hubble's observations have been important in all areas of astronomical research, including the still-unexplained discovery that the universe is expanding at an increasingly faster rate and that galaxies formed quite early after the Big Bang explosion that created the universe 13.7 billion years ago.
Hubble made the first measurements of gases in the atmosphere of a planet in another solar system and found evidence that raw materials for planet formation are very common.
