NASA has begun counting down to the launch of space shuttle Discovery's final mission to the International Space Station. The 39th flight of NASA's most flown shuttle is scheduled to last 11 days, beginning at 4:50 pm EST on Feb. 24 from Kennedy Space Center in Florida.

NASA's weather forecasts expect 80 percent chance of acceptable or favorable conditions at the launch time. The 11-day final flight will involve six-member crew delivering a storage module, a science rig and spare parts to the international space station.

The crew astronauts includes Commander Steve Lindsey, Pilot Eric Boe and Mission Specialists Alvin Drew, Steve Bowen, Michael Barratt and Nicole Stott. They will be accompanied by Robonaut 2 (R2), the first human-like android.

Bowen and Drew will conduct two spacewalks to install new components and perform maintenance. For both spacewalks, Bowen will be designated extravehicular crew member 1 (EV1), and will wear the suit bearing red stripes. Drew, who will be making his first two spacewalks on STS-133, will be extravehicular crew member 2 (EV2) and will wear the unmarked suit.

Discovery has flown more than any other shuttle with 38 flights, completed 5,247 orbits and has spent 322 days in orbit. Discovery's current flight will be its 39th and final voyage into space before NASA retires its orbiter fleet later this year.

After the orbiter has retired, NASA will offer Discovery to the Smithsonian Institution's National Air and Space Museum for public display and preservation as part of the national collection.

Discovery is scheduled to land on March 7 at 11:50 am EST at the Kennedy Space Center in Florida. At the time of its landing, Discovery would have traveled more than 143 million miles over the course of 26 years.