The 16 day mission which will be its 25th flight into Space and the 11th calling at the International Space Station, will deliver $2bn worth of astrophysics equipment to the ISS, designed to search Space for antimatter.
The final countdown for the launch of the last shuttle will take place in July when Atlantis will fly for the last time, bringing to an end the 30 year NASA shuttle program.
What follows next will be a significant period of time when the US will be unable to put astronauts into Space under its own steam, relying totally on the Russian Soyuz program. The future of American led missions into Space will only restart again once private companies have developed and built rockets to take over the job, with 2015 being estimated as the earliest date for new launches to begin.
Uneasy times ahead for the USA Space program I think!