The countdown for space shuttle Discovery’s launch on the STS-133 mission to the International Space Station is under way. The count began on-time at 3 p.m. EST with the team at NASA Kennedy Space Center’s Launch Control Center not working any significant issues. The weather forecast calls for an 80 percent chance of acceptable conditions at launch time. Countdown clocks are ticking backward from the T-43 hour point. With seven holds built in, the countdown will lead to the scheduled launch of Discovery at 4:50 p.m. on Thursday, Feb. 24. The shuttle is in good shape, NASA Test Director Jeff Spaulding said Monday morning. This mission is slated to be Discovery’s last flight into space. The spacecraft has gone into orbit 38 times before. Discovery launched its first mission Aug. 30, 1984.