Workers watch is lifted up the mobile service tower for mating with the Boeing Delta II Heavy rocket seen in the background.

Workers at Pad 17-B, Cape Canaveral Air Force Station, watch as one of the last Solid Rocket Boosters (SRBs) is lifted up the mobile service tower for mating with the Boeing Delta II Heavy rocket (seen in the background). The Delta II will launch the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft Aug. 2, bound for Mercury. The spacecraft is expected to reach orbit around Mercury in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.