At the start of 2011, as NASA was closing in on the root cause of the cracks in Discovery's tank, the agency was rocked by news that Giffords, a Democrat representing Arizona's 8th Congressional District, had been shot in the head Jan. 8 at point blank range during a public meeting in front of a Tucson supermarket.

File image of commander Mark Kelly and Rep. Gabrielle Giffords, who were married in 2007. Credit: Giffords Flickr photostream

Giffords was one of 20 people hit when Jared Loughner, a 22-year-old college dropout, allegedly opened fire with a semi-automatic pistol. Six were killed, including a federal judge and a 9-year-old girl.

"It was extremely terrible," said Johnson, Endeavour's pilot. "The news reports, for a period of time believed that (Giffords) had been killed. We had socialized as a crew just a few short weeks prior, and my daughter had spent some time with Gabby on a one-on-one level. She was devastated."

President Obama flew to Arizona for a memorial service, telling friends and family members "there is nothing I can say that will fill the sudden hole torn in your hearts."

"But know this: The hopes of a nation are here tonight. We mourn with you for the fallen. We join you in your grief. And we add our faith to yours that Representative Gabrielle Giffords and the other living victims of this tragedy will pull through."

One week after the assassination attempt, NASA announced that Kelly, who had flown to Tucson the day of the shooting, would be taking a leave of absence. Rick Sturckow, a veteran shuttle commander, took his place in crew training exercises and simulations.

But one month later, Kelly announced he would resume training to command Endeavour, saying his wife "would be very comfortable with the decision I made."

"Her days are filled, from the time she gets up at eight o'clock until after 6 p.m., with six hours of speech, occupational and physical therapy," Kelly told reporters in March. "So she's got very busy days, and meals in between.

"And I started to think about STS-134, about the mission, my crew, the fact that I've been training for it for nearly a year and a half. And considering a bunch of other factors, including what Gabrielle would want me to do and what her parents and her family and my family would like, I ultimately made the decision that I would like to return and command STS-134."

Chief astronaut Peggy Whitson supported Kelly's decision.

"Mark had to make the first part of this decision," she said. "We weren't going to ask him to command 134 unless he felt comfortable and ready to do that. In addition to feeling comfortable, he has an incredible support group, which made us more comfortable with the fact that he had folks to help him through this process and that it would make it a doable thing for him to perform the mission."

Asked about critics who might question his decision to spend time away from his wife at a critical point in her recovery, Kelly said "they don't understand a few things."

"They don't know her very well, so they don't know what she would want," he said. "She is a big supporter of my career, a big supporter of NASA. She really values the mission of NASA. What we do and what the nation gets from that are very high on her list of things she really treasures about this country. So I think they don't understand that, and they also don't understand her condition or the support system that I have in place.

"I think if they had more details about those things, you'd probably have less people being critical. But I think in any decision there's a lot of interest in, you're going to have people on both sides."

Kelly told the CBS Evening News the week before launch that Giffords was "very excited" about the pending trip to Florida.

"It's going to be a little bit more complicated than your average person," he said. "But I've got folks in my office that have been focused on that. And, you know, she has some security and certainly there are some medical needs that need to be met, but we've been planning it for a couple weeks now. It's not anything too significant."

Kelly said earlier he still feels angry from time to time about what happened to his wife and the other victims of the Tucson shootings.

"When a traumatic event happens, there are those different steps that you go through," he said. "I think I very quickly got to 'angry' on the first day this happened. I can't remember what step two was, but I think I skipped right over that one. At times, I'm angry about what happened to her. ... It's really an unfortunate, tragic situation."

But he said that anger played no role in his decision to resume training.

"Absolutely not," he said. "What I use to evaluate whether I want to come back to be commander of this mission has nothing to do with being angry and everything to do with what is right for NASA first, and then for me and my family."

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