NASA officials announced that the Monday launch has been scrubbed after continuing mechanical problems developed with a tracking airplane and a substitute ship has not been properly positioned to take over tracking of the Dawn spacecraft. The earliest launch date is now Sunday, July 15, 2007.

Either a properly functioning airplane or a correctly located ship is needed in order to track the spacecraft after it launches from NASA’s launch complex in Florida.

On Thursday, lightning over the skies of east-central Florida postponed Saturday’s launch of NASA’s Dawn mission to the dwarf planet Ceres and the asteroid Vesta.

The mission had problems even before the bad weather occurred. The fueling of the second-stage rocket, which will launch Dawn to the dwarf planet and asteroid, had been delayed due to hot conditions on the exterior payload walls of the rocket (its fairing), which prevented the super-cold oxidizer propellant from being loaded.

Even if NASA had been able to launch on Sunday, July 8, 2007, the day held little promise of better weather as forecasters are predicting a likely chance for more bad weather.

NASA now has set Sunday, July 15, 2007 as its earliest launch day for the Dawn mission.

NASA officials are wanting to launch the spacecraft by July 19th. If unable to do so, they will have to wait late September or early October. By the end of October, however, the two bodies that the Dawn spacecraft will visit—dwarf planet Ceres and asteroid Vesta—will begin to drift apart.

It will be much more difficult to rendezvous with both bodies if the launch of the mission is delayed this long. Ceres and Vesta will not be this close together for another fifteen years.

However, it will not be impossible because the spacecraft uses an ion-drive propulsion system. The high-tech propulsion system can be stopped and restarted frequently, which allows for much more flexible launch windows than if spacecraft are propelled by chemical rocket systems, which are only started a few times for major course changes.

Dawn is expected to fly past Vesta in October 2011 in order to investigate its lava flows, which may help answer how it was initially formed. Later, in February 2005, Dawn will rendezvous with the dwarf planet Ceres.

For more information on NASA’s ion powered Dawn mission to Ceres and Vesta, go to the iTWire article titled “NASA’s Dawn mission to asteroids powered with high-tech ion drive”.

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