The countdown to liftoff of NASA's MAVEN spacecraft aboard a United Launch Alliance Atlas V rocket continues to progress smoothly. At 11:48 a.m. EST, liquid oxygen began flowing into the rocket's first stage booster. Liquid oxygen loading of the Centaur upper stage is about 50 percent complete. There are no technical issues and launch remains targeted for 1:28 p.m. from Cape Canaveral Air Force Station's Space Launch Complex 41.