Factbox: Space shuttle Endeavour's final mission

(Reuters) - Space shuttle Endeavour embarks on its 25th and final flight on Friday to deliver the $2 billion Alpha Magnetic Spectrometer particle detector, supplies and spare parts to the International Space Station.

The flight will be the 134th for NASA's shuttle program, with one mission to follow this summer before the fleet is retired.

Here are highlights of Endeavour's mission, which is scheduled to last up to 16 days:

* Endeavour is carrying a new type of science instrument, called the Alpha Magnetic Spectometer, or AMS, which will make detailed studies of high-energy cosmic rays. The device, built by an international consortium of 60 research agencies, will be mounted outside the space station.

* Also aboard Endeavour are spare parts, including 10 circuit breakers, two communications antennas, a tank of ammonia coolant, a high-pressure oxygen tank for the station's airlock and a spare arm for the station's robotic crane.

* Endeavour's astronauts will conduct four spacewalks to install a materials science experiment, refill an ammonia coolant reservoir and perform other station maintenance.

* A 50-foot (15-meter) extension for the shuttle's robot arm, developed for in-flight inspections after the 2003 Columbia accident, will be left behind at the station for use by the station's robotic crane.

* The crew will also test sensors being developed for NASA's new deep-space exploration vehicle called Orion.

* Endeavour will be the second of NASA's three space shuttles to be retired this year. After its mission, Endeavour will go on display at the California Science Center in Los Angeles.

(Reporting by Irene Klotz; Editing by Kevin Gray)