NASA schedules launch date for comet-chasing probe

January 9, 2005 A spacecraft designed to chase a comet and crash onto its surface is scheduled for a launch on January 12, 2005 and 1:48 p.m. EST. In early July the probe, named Deep Impact, will approach Comet Tempel 1 to take a number of measurements and photographs. The probe will then split in two, with one part &mdash; containing an 820-pound copper weight &mdash; propelling itself towards the path of the comet. Twenty-four hours after separation the comet will crash into the slower-moving impactor, creating a crater 100 meters wide.

Astronomers know little of the nuclei of comets, and this mission was designed to determine the make-up of comets' cores. The event will be watched by many instruments: there are two cameras on the part of the probe that is not getting destroyed, a camera on the impactor will broadcast almost until the crash, and telescopes around Earth will also be aimed at the point of the impact. Scientists hope that by studying the depth of the crater and the material ejected from the comet in the crash they will get a better idea of the core's composition.

The probe is named Deep Impact after a Hollywood movie of the same title. In the movie a comet is bombarded with warheads in order to steer it off a collision course with Earth. Unlike the movie, however, the goal of this mission is not to destroy the comet. Indeed, probe's size makes it very unlikely that the comet will suffer more than a crater: the comet is 3.7 miles wide while the probe is about the size of a washing machine.

The probe will be launched aboard a Delta II rocket from Cape Canaveral in Florida.