The final launch of the space shuttle Endeavor is expected to take place shortly before 9am EST, and promises to be an emotional moment for the shuttle's commander, Mark Kelly.

Kelly's wife, U.S. Rep. Gabrielle Giffords, D-Arizona, traveled to Florida Sunday night with high hopes of watching the shuttle's ascent tomorrow morning.

Gabrielle landed safely in Florida together with the family of Greg Johnson, another astronaut on the shuttle crew, Gifford's Facebook page said.

Giffords was shot in the head during a January 8 assassination attempt at a public event in Tucson, Arizona. She has since been recuperating at a hospital in Houston.

The launch will also mark the end of a long history of service for the Endeavour shuttle itself.

The final launch was delayed by two weeks as engineers battled to resolve an electrical problem that plagued the original launch dates.

Mission managers gave the green light Saturday for the final voyage of Endeavour to occur on May 16. Forecasters put the odds of acceptable weather at 70 percent.

Extensive work was needed to fix a faulty heater system in the engine compartment. The heaters keep fuel from freezing in the line, critical in preventing it from rupturing in the cold vacuum of space.

NASA replaced a distribution box that shorted out a circuit supplying power to heaters for the orbiter's hydraulics system.

The NASA space shuttle will take with it the $2bn Alpha Magnetic Spectrometer particle detector to the International Space Station.

The device is designed to give scientists their first detailed study of the electrically charged particles streaming through the universe.

It could also reshape modern understandings of the universe in a similar way that the Hubble Space Telescope pioneered new frontiers in astronomy.

The pictures painted by AMS, which was assembled at the CERN physics research center near Geneva, could bring to light the universe's so-called dark matter -- material that is so far unaccounted for but necessary to explain what is observable.

Endeavour is the second-to-last shuttle mission for the 30-year US program. Atlantis will mark the end to the program in in June and July.

NASA is winding down its space shuttle operations this summer as it tries to save money, which will leave American and European astronauts with only Russian rockets as options for going into space.

In February, the space shuttle Discovery, NASA's oldest and most travelled spacecraft, made its final voyage into space.

The country is focusing on inspiring 3rd part companies to put astronauts in orbit using privately run launch, transport and services companies.

NASA will now focus its resources on deep space exploration, such as potential landings on asteroids and, eventually, Mars.