(CNN) -- For Mark Kelly, commander of space shuttle Endeavour, there was good news leading up to the launch.
His wife, Arizona Congresswoman Gabrielle Giffords, is there to watch, less than four months after a bullet tore through her head and nearly took her life.
At one point, it was uncertain whether Kelly would even stay on to command the mission. He was training while spending nearly every evening at his wife's side while she was hospitalized.
"Flying in space is a very difficult thing to give up," Kelly told CNN before the January shooting. "I remember after my last flight thinking, 'Well, maybe this is the last time I'm gonna do this.' And you know, you go a couple of months out and you're like, 'Oh, I really hope this is not the end of my flying career.' " Kelly added, " I know when I get back ... from this last flight of Endeavour, I'll be thinking the same thing: I can't really give this up. I've got to figure out a way to get back into space."
As the space shuttle program winds down with the last launch scheduled this summer, many in the astronaut corps are wrestling with what to do next. For the foreseeable future, Russian rockets will be the only way for U.S. astronauts to get to space.
Mike Fincke, an Endeavour mission specialist, has spent a year in space but is flying on a shuttle for the first time.
"I think all of us with all the changes that going on with our country's space program and NASA, all of us professional astronauts are looking into our hearts to see what we're gonna do next," Fincke said.
"I really want to stay. I want to stay here at NASA. I believe in what we are doing."
Four spacewalks are planned for this mission to prepare the station ready for the time when shuttle crews can't get up there. The spacewalkers will retrieve experiments, install new ones, refill tanks and lubricate parts.
In its cargo bay Endeavour is carrying the Alpha Magnetic Spectrometer. At $1.5 billion, it is the single most expensive piece of equipment a space shuttle has ever carried.
The AMS is designed to capture space particles like anti-matter and dark matter, which scientists know very little about but believe exist. The AMS will be mounted outside the International Space Station. If it's successful, it could lead to a better understanding of how our universe began and evolved.
For the astronauts, the two-week-long mission will be the last time they fly on a shuttle and it will be the end of the space road for Endeavour. The vehicle was build as a replacement for Challenger, which was lost in 1986.
Endeavour flew its first mission in 1992. It's flown numerous space station construction missions and the first Hubble servicing mission.
Endeavour and the other orbiters have been remarkable flying machines, said pilot Gregory Johnson: "We have put satellites up into orbit. We have done mapping of the whole topography of the Earth. We have taken up the Hubble Telescope and serviced it several times. And we've built this huge space station. The vehicle has done its job."
When Endeavour returns it will be cleaned up and made ready for its journey to the California Science Center in Los Angeles, its new permanent home.