NASA's Busy Launch Schedule

via Space.com as well.

Problems with NASA's Dawn mission to examine the dwarf planet Ceres, as well as asteroid Vesta could hamper other space missions, including the upcoming August shuttle Endeavor's construction mission to the ISS and the Phoenix science mission to Mars. The Dawn mission's issues include a damaged solar panel, mechanical issue with the launch vehicle thought to have been caused by rough weather during transport to the launch site, and a balky assembly crane.

"Todd May, the deputy associate administrator for programs at NASA headquarters in Washington, said both the asteroid-belt-exploring Dawn and Mars-bound Phoenix missions are very sensitive to launch changes. To reach their targets, each must leave Earth within a defined window of time. "They're both planetary, so they have limited launch windows," May said. "It's a hard window constraint to get (Phoenix) off by Aug. 25," he continued, so any movement of the Dawn launch window could also interfere with Phoenix's launch-as well as the STS-118 shuttle mission, expected to launch on Aug. 7."

The Dawn mission is intended to gather evidence about the early years of the solar system's formation by examining the mineral content of the two leftover chunks of rocky materials. Ceres, thought to possibly have frozen ice, will be visited by the probe in 2015, four years after the same craft visits Vesta in 2011. More on the science behind the mission here.