Halley's comet

A radical mission to excavate the interior of a comet has been selected as one of the next two flights in NASA's Discovery Program, the agency announced today.

The comet mission, called Deep Impact, will be managed by the Jet Propulsion Laboratory, led by Dr. Michael A'Hearn from the University of Maryland in College Park, and built by Ball Aerospace in Boulder, Colo. The mission will send a 500-kilogram (1,100-pound) copper projectile into comet P/Tempel 1, creating a crater as big as a football field and as deep as a seven-story building. A camera and infrared spectrometer on the spacecraft, along with ground-based observatories, will study the resulting icy debris blasted off the comet, as well as the pristine interior material exposed by the impact.

"Comets are leftovers from the birth of the Sun and the planets, and Deep Impact will punch through the dark crust of P/Tempel 1 to give us our first look at what's inside," said JPL director Dr. Edward Stone.

James E. Graf will serve as project manager at JPL. Graf currently heads NASA's QuikScat mission to measure sea surface winds over the global ocean, successfully launched last month.

Deep Impact will be launched in January 2004 toward an explosive July 4, 2005 encounter with P/Tempel 1. Those impacts will occur at an approximate speed of 10 kilometers per second (22,300 mph). The total cost of Deep Impact to NASA is $240 million.

NASA also today announced the selection of another new Discovery mission, one that will map the pockmarked surface of Mercury. That spacecraft, to be built and managed by the Johns Hopkins University's Applied Physics Laboratory, Laurel, MD, is known as Mercury Surface, Space Environment, Geochemistry and Ranging mission, or Messenger.

"These low-cost missions are both fantastic examples of the creativity of the space science community," said Dr. Edward Weiler, associate administrator for space science at NASA Headquarters in Washington, DC. "Deep Impact presents a special chance to do some truly unique science, and it is a direct complement to the other two comet missions already in the Discovery Program."

Those missions are Stardust, managed by JPL, launched in February 1999 on a journey to gather samples of comet dust and return them to Earth, and the Comet Nucleus Tour (CONTOUR) that will launch in June 2002 and fly closely by three comets. CONTOUR is managed by Applied Physics Lab of Johns Hopkins University.

Another Discovery mission managed by JPL was Mars Pathfinder, which landed successfully on the red planet in 1997, accompanied by a small robotic rover named Sojourner. The Pathfinder mission returned hundreds of images and thousands of measurements of the Martian environment.

JPL also manages the Discovery mission called Genesis, launching in January 2001, which will gather samples of the solar wind and return them to Earth.

In this latest round of Discovery missions, NASA selected Deep Impact and Messenger from 26 proposals made in early 1998. The missions must be ready for launch no later than Sept. 30, 2004, within the Discovery Program's development cost cap of $190 million in fiscal 1999 dollars over 36 months and a total mission cost of $299 million. The Discovery Program emphasizes lower- cost, highly focused scientific missions.

JPL will manage the Deep Impact mission for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology, Pasadena, Calif.

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