The Space Shuttle Endeavour blasted off on the next-to-last shuttle flight Monday morning under the command of Mark Kelly, the husband of Rep. Gabrielle Giffords.

Five months after taking a bullet to the the head during the infamous Tucson, Ariz. shooting spree, the congresswoman watched the launch in private from the Kennedy Space Center.

"She has been working really hard to make sure her doctors would permit her to come," Kelly said of his wife.

"It seems she understands everything. I mean, if not everything, then almost everything," Pia Carusone, Giffords' chief of staff, said. "So she is really there. She follows directions; she laughs at jokes, recognizes friends."

The shuttle crew wore blue bracelets to celebrate Giffords' recovery.

As many as 45,000 guests crowded the Cape Canaveral, Fla., launch site. Several hundred thousand more jammed local area roads and towns for a glimpse of the spectacular sight.

The mood of the crew of six Monday morning was upbeat.

"Took my last shower for a few weeks," reported astronaut Mike Fincke in a tweet before the launch. "The flight docs gave a good look-over. My only issue: too much boyish enthusiasm."

Monday's launch, the second to last for Endeavor, went off without a hitch. Late last month, an electrical problem halted the countdown. 

"Everything is in really great shape, really no issues at all," Mike Moses, chairman of NASA's Mission management team, said.

Endeavour and its six astronauts will arrive at the International Space Station on Wednesday.

The shuttle's experienced crew will deliver and install a $2 billion particle physics experiment during the 16-day flight, as well as spare station parts.

One final shuttle mission remains by Atlantis in July, bringing the 30-year shuttle program to end.