AirshowAstrotech Space Operations facilities near KSC, workers check the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft as it rotates on the turnover fixture. Workers will perform the propulsion system phasing test - firing gas through the thrusters in order to verify that the right thrusters fire when expected - as part of prelaunch testing at the site. Launch is scheduled for May 11 from Pad 17-B, Cape Canaveral Air Force Station. The spacecraft will fly past Venus three times and Mercury twice before starting a year-long orbital study of Mercury in July 2009.