Astronauts brace for final landing
Washington - Nostalgia, bitter sweet emotion and jitters about the future of the US space programme were on view on Wednesday aboard Atlantis as its crew prepared to return home on the last-ever shuttle mission.
Countdown clocks are ticking toward a Thursday pre-dawn touchdown in Florida, where the eyes of the world will turn to witness history as America's most successful space program comes to an end after 30 years.
The crew of four have been preparing for re-entry after a final shuttle mission to the International Space Station, but the US astronauts said the magnitude of what was happening only settled in once they floated away from the ISS on Tuesday.
"It may seem like a sort of an ending, and I suppose to a degree it is. The space shuttle has been with us at the heart and soul of the human space flight programme for about 30 years, and it's a little sad to see it go away," commander Chris Ferguson said as the crew sat for a series of TV interviews on Wednesday.
"It's going to be tough," he said, when he and pilot Doug Hurley bring the wheels of Atlantis to a halt at Kennedy Space Centre after a touchdown scheduled for 05:56 (09:56 GMT).
"It's going to be an emotional moment for a lot of people that dedicated their lives to the shuttle programme for 30 years. But we're going to try to keep it upbeat.... We're going to try to make it a celebration of the tremendous crowning achievements that have occurred."
As the age of the shuttle - which has carried US astronauts into space longer than any other vessel - draws to a close after 37 dramatic rendezvous with the space station, their crews on Monday exchanged embraces and kisses before shutting the hatches separating them for a final time.
In the United States, millions of Americans have witnessed no other form of human space transport in their lifetime.
Mission specialist Rex Walheim said he was optimistic about the future of the US space programme, but acknowledged "we're in a kind of a transition period, which is a little bit uncomfortable".
Nasa aims to turn over low-orbit space travel and space station servicing to commercial ventures, with a commercial launcher and capsule built by a private corporation in partnership with Nasa ready to fly sometime after 2015.
"That'll free up Nasa to do the heavy lifting of the beyond low-Earth orbit flights," to what Walheim described as "harder destinations" like an asteroid, or Mars.
"It'll be hard, but we'll get there, going farther and farther, and we'll get to new places real soon," he said.
Until the private sector fills the void, the world's astronauts will rely on Russian Soyuz rockets for rides to the ISS.
Over the course of the programme, five Nasa space shuttles - Atlantis, Challenger, Columbia, Discovery and Endeavour - have comprised a fleet designed as the world's first reusable space vehicles.
Besides the prototype Enterprise that never flew in space, only three have survived after Columbia and Challenger were destroyed in accidents that killed their crews.
At a time of US budget austerity, President Barack Obama has opted to end the programme that has averaged about $450-500m for each of its 135 missions. He also cancelled Constellation, a project that aimed to put US astronauts back on the Moon by 2020 at a cost of $97bn.
Hurley paid tribute to the thousands of men and women who worked on the missions over the decades.
"We're really looking forward to bringing her home tomorrow," he said.
Mission specialist Sandy Magnus said she was not sure if she'd ever return to space and so was trying to "savour every moment" on Atlantis, getting "those last glances out the window of our beautiful Earth and try and print those on my memory".
Nasa was forecasting ideal weather conditions for the landing. The Empire State Building in New York announced it will light up in red, white and blue overnight to serve as a beacon for the astronauts' historic return.
Commander Ferguson called on Americans back home to tune in to the final landing.
"Take a good look at it and make a memory," he said, "because you're never going to see anything like this again."