Endeavour is targeted for launch at 4.39am EST (0939 GMT), on a 13-day mission to deliver a final connecting hub and viewing port to the International Space Station.
Nasa managers on Wednesday settled on February 7 to kick off their final year of shuttle flights, uncertain about what programmes will follow.
Endeavour is targeted for launch at 4.39am EST (0939 GMT), on a 13-day mission to deliver a final connecting hub and viewing port to the International Space Station.
Four more flights will follow to complete the $100 billion orbital outpost, a project of 16 nations, before year's end.
"A lot of us have a lot of years in this programme, so it's going to be sad to see it end," said shuttle launch director Mike Leinbach. "I think we have a good future. It's not going to be the same, but it'll be good."
NASA has been working on a follow-on programme called Constellation to return astronauts to the surface of the moon and prepare for human exploration of the solar system.
However, a top-level panel of advisors tapped by the Obama administration to review the program determined that budget cuts already have undermined the effort to the point that it no longer made sense to continue. It could be revived with a budget boost of about $3 billion a year, the panel said.
Nasa currently gets about $18 billion a year, more than half of which is spent on human space flight programmes.
President Barack Obama will unveil Nasa's budget request next week as part of his overall US spending plan for the year beginning October 1. The White House has said most agencies' budgets will remain flat, in an attempt to stem a federal budget deficit expected to reach $1.35 trillion, according to the Congressional Budget Office.
Nasa's highest priority is to safely complete the remaining shuttle missions, undistracted by concerns about impending layoffs that will gut the shuttle workforce over the next several months.
"If we don't, the programme will stop even sooner," Leinbach told reporters.
Nasa hopes to receive funds to keep the space station flying through at least 2020, five years beyond its currently planned lifetime.
A structural analysis is under way to determine if the outpost will be safe to fly beyond 2015, and Nasa also plans to stock it with additional batteries, life-support equipment and other gear.
The agency already has turned over crew transport services to the Russians — at a cost of $50 million per seat — and is considering using commercial US firms to fly crews to the station. Several companies are vying for Nasa study contracts to develop passenger spaceships that can reach orbit.
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