If all goes to plan the shuttle should set off from the Kennedy Space Centre in Florida to the International Space Station at just after 8.56am (1.56pm UK time).
It is to be Endeavour's 25th and final mission. After returning to earth in 16 days time she will be retired to a Los Angeles museum.
But it's no routine mission. Endeavour will be carrying her most expensive payload ever - a $2billion particle physics experiment known as the Alpha Magnetic Spectrometer (AMS) designed to probe the unknown reaches of space and help us understand the secrets of the universe.
The seven-ton machine, which was built through a collaboration of 16 nations, will carry out a comprehensive survey of cosmic rays as it studies the universe with, scientists hope, far more detail than is possible from earth.
The AMS project involved 600 physicists in 60 research organizations around the world and is spearheaded by Nobel laureate Samuel Ting of the Massachusetts Institute of Technology.
It will test the long-standing Big Bang theory - by checking for any large quantities of anti-matter - which theorists suspect was created when the universe was born.
It will also be used to examine the nature of dark matter, the material that makes up most of the universe.
Scientists hope it might help them to understand how the Universe came into being and how it is constructed? Read More