Despite facing looming technical problems with a launch vehicle and assembly crane, NASA officials said in a telephone conference today that they are intent on a July 7 launch of the Dawn mission.

If the launch vehicle and assembly crane aren?t repaired, however, the U.S. space agency faces a ?traffic jam? into space that could cost around $25 million.

Rough weather caused mechanical difficulties in components attached to the launch vehicle during its transportation, a NASA official said.

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.

In addition to the launch problems, one of Dawn?s solar panels was damaged while at NASA?s Kennedy Space Center during processing. On June 18, NASA said technicians repaired damage, which was caused by an ?errant tool.?

The Dawn mission team will decide on July 2 whether they will launch Dawn July 7. May explained that scrubbing the launch would cost around $25 million, but said the team is moving ?full steam ahead? for a launch next Saturday.

?To some extent there?s no looking back,? he said of an agreement to launch. ?We will be watching the weather closely and by that time have the launch vehicle issues out of the way.?

NASA hopes to use Dawn to investigate two leftover chunks of the early solar system. Ceres was once called the largest asteroid and is now re-labled as a dwarf planet. The other target: asteroid Vesta. Both objects reside in the asteroid belt between Mars and Jupiter.

The two bodies share similar properties with Earth, and astronomers believe Ceres, at about 590 miles wide, might harbor ice beneath its dusty shell. Vesta is a mostly dry rock roughly 330 miles in diameter.

If all goes as planned, the spacecraft will first orbit Vesta in 2011 and then Ceres in 2015. At each stop, Dawn will collect detailed information and photographs of each rock, such as their shape, size, composition and even clues to their internal histories. Scientists think such information about Earth?s asteroid-belt cousins could reveal clues as to how the solar system formed.