for National Geographic News
The launch of NASA's Deep Impact mission to smash a spacecraft into a comet on July 4, 2005, has been delayed until at least January 12. That means the mission team will have fewer potential launch dates to choose from, because their target comet will only be in range for a short time.
But scientists said this week that they are still confident the mission will go off as planned.
"We expect to provide some great fireworks for all our observatories next Fourth of July," engineer Rick Grammier said at a news conference this week. Grammier is the Deep Impact project manager at NASA's Jet Propulsion Laboratory in Pasadena, California.
If all goes as planned, a flyby spacecraft will shoot a projectile about the size of a trash can into the surface of a frozen ball of ice and rock, comet Tempel 1, creating a crater the size of a football stadium.
The mission is the first time a spacecraft will touch the nucleus of a comet. Scientists hope to find out more about what the comet is made of.
Comets are seen as the building blocks of the solar system. Many scientists believe comets are the source of most of the water and organic material that was long ago delivered to terrestrial planets.
Planning for the Deep Impact mission began in 1999. It should culminate on July 4, 2005, when the "impactor" spacecraft is expected to smash into comet Tempel 1 at 22,000 miles an hour (37,000 kilometers an hour).
Since the flyby spacecraft is traveling at almost the same high speed, scientists have only a 13-minute, 20-second window to make their observations before launching the projectile, which is equipped with a camera and is built to reach the comet largely on autopilot.
The launch was initially scheduled to take place at the end of this month, but has been delayed at least twice. The latest delay came after scientists determined that further software testing was needed.
Boeing, the spacecraft manufacturer, also decided to replace a part on the Delta 2 rocket that will carry the craft.
The craft must launch from Florida's Cape Canaveral space station by January 28 in order to make a rendezvous with Tempel 1 on July 4, 2005. Otherwise, the scientists will have to choose another, less enticing target.
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