AirshowWorkers at Astrotech Space Operations in Titusville, Fla., remove the cover from the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft inside the nonhazardous payload processing facility. Final assembly and testing will be completed at this site. The spacecraft will return to the hazardous processing facility when ready for fueling, spin balance testing and mating to the upper stage. MESSENGER is scheduled to launch no earlier than July 30 from Cape Canaveral Air Force Station. MESSENGER is a scientific investigation of the planet Mercury, the least explored terrestrial planet. Understanding Mercury and how it was formed is essential to understanding the other terrestrial planets and their evolution. The MESSENGER mission will orbit Mercury after making two flybys of the planet, using data collected during the flybys as an initial guide to perform a more focused scientific investigation of this mysterious world. The spacecraft will enter Mercury orbit in March 2011 and carry out comprehensive measurements for one full Earth year.