Despite Delay, Dawn Still on Track to Rendezvous with Asteroids

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  Space News Business

Despite Delay, Dawn Still on Track to Rendezvous with Asteroids

By BRIAN BERGER
Space News Staff Writer
posted: 31 July 2007
04:16 pm ET








WASHINGTON —


A two-month delay in the launch of NASA’s Dawn spacecraft is expected to add an estimated $25 million to the mission’s $450 million price tag, but not compromise any of its science objectives.

The delay was the result of a combination of weather delays, technical problems and launch pad availability issues.

The Orbital Sciences-built Dawn spacecraft was on the launch pad and ready to embark on its eight-year journey to the rocky protoplanetsVesta and Ceres when thunderstorms near Cape Canaveral, Fla.,




prevented fueling of the Delta 2 rocket’s upper stage. That initially pushed




a planned July 6 liftoff out to July 8. Mechanical issues with a telemetry relay aircraft and the unavailability of a tracking ship further delayed the planned launch to July 9 and then to July 15 before NASA ultimately decided to wait and launch Dawn when a new, longer window opens Sept. 7.



Jim Green, director of NASA’s planetary science division, told reporters here July 9 that in addition to a run of bad weather at Cape Canaveral, high seas in the southeastern Atlantic Ocean were keeping the tracking ship OTTR (short for Ocean-going Transportable Test and Evaluation Resource) from reaching its destination off the coast of Africa in time to support a launch any earlier than July 15.

But waiting until then, Green said, would have given NASA just a few days of late afternoon launch windows – prime time for summer thunderstorms in the nearly tropical climate – to launch Dawn before preparations for the Mars Phoenix lander’s early August liftoff would start to be affected.

Further complicating NASA’s calculations, Green said, was the knowledge that once the upper stage of Dawn’s Delta 2 rocket was loaded with corrosive hydrazine fuel, the rocket would have to lift off in July or have its upper stage replaced – a costly setback both in terms of time and money. NASA officials initially thought that replacing the upper stage could be accomplished in time to attempt an October launch.



But NASA spokesman Dwayne Brown said the agency subsequently learned that United Launch Alliance could not refurbish or replace the upper stage that quickly. Alan Stern, NASA’s associate administrator for science, told Space News that the wait for a new upper stage and launch slot could be two years. Dawn’s opportunity to visit both Vesta and Ceres ends in late October and does not come around again for 15 years.

“So the stakes were very high,” Stern said. “If we wet the upper stage and had not been able to fly we’d be sitting there with all that hardware. We’d have to build another second stage, wait in line, and then we’d have to pick one but not both asteroids.”



Green said launching in September has its advantages. For starters, the launch window runs until mid




October, giving NASA some five or six weeks to send Dawn on its way.


Tariq

Malik contributed to this story from New York.