for National Geographic News
NASA engineers launched their Deep Impact spacecraft today. The mission aims to smash an 820-pound (370-kilogram) projectile into a comet on July 4, 2005.
"We expect to provide some great fireworks," engineer Rick Grammier said at a recent news conference. Grammier is the Deep Impact project manager at NASA's Jet Propulsion Laboratory in Pasadena, California.
If all goes as planned later this summer, 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 December, 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.
Today the craft had a one-second window to launch from Florida's Cape Canaveral space station in order to make a rendezvous with Tempel 1 on July 4, 2005.
Tempel 1 was discovered in 1867 by astronomer Ernst Tempel. The comet probably formed beyond the planet Neptune in the Kuiper belt, a disk-shaped region that is the source of most short-period comets, comets that orbit within our solar system.
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