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JPL To Assist On Comet Mission

JPL Universe
June 21, 2002

Contour prepares for July 1 launch

Set to visit and study at least two comets, NASA's Comet Nucleus Tour (Contour) should provide the first detailed look at the differences between these primitive building blocks of the solar system, and answer questions about how comets act and evolve. The mission is being prepared for a July 1 launch from Kennedy Space Center.

JPL will provide navigation and Deep Space Network support for the mission, and JPL astronomer Dr. Don Yeomans, manager of NASA's Near Earth Objects Program Office, is a Contour science team co-investigator.

Contour is scheduled to lift off on a three-stage Boeing Delta II expendable launch vehicle during a 25-day launch window that opens July 1 at 2:56 a.m. Eastern time. The spacecraft will orbit Earth until Aug. 15, when it should fire its main engine and enter a comet-chasing orbit around the sun.

Contour's flexible four-year mission plan includes encounters with comets Encke, Nov. 12, 2003, and Schwassmann-Wachmann 3, June 19, 2006. Contour will examine each comet's "heart," or nucleus, which scientists believe is a chunk of ice and rock, often just a few kilometers across and hidden from Earth-based telescopes beneath a dusty atmosphere and long tail.

"The Contour mission will be NASA's second mission dedicated solely to exploring these largely unknown members of our solar system," said Dr. Colleen Hartman, director of the Solar System Exploration Division at NASA Headquarters in Washington. "Contour joins our other operating mission, Stardust, which is on its way to bring a sample of a comet back to Earth, and Deep Impact will launch next year. These missions all help us find answers to the fundamental questions of how our planet may have formed and evolved, and how life may have begun on Earth and perhaps elsewhere in the Universe."

Comets are "the remnants of the outer solar system formation process," Yeomans said in a prelaunch briefing. The instruments on Contour, he added, will determine the chemical composition of the comet - helping in turn to determine whether a comet might have brought much of the Earth's oceans and its atmosphere, as well as carbon-based molecules, to the Earth's surface.

Yeomans said the "genius" of the Contour mission design is that "we're not chasing comets around the solar system; we're using Earth swingbys to allow them to come to us." The encounters are taking place very close to Earth (less than 50 million kilometers or 31 million miles), which, he said, "makes communications easy, but it also allows professional, ground-based astronomers, as well as amateur astronomers and the public, to participate in a very meaningful way." The comets will be bright enough to be seen with binoculars about the same time as Contour is looking at the comet's nucleus, he said.

Members of the JPL navigation team include Tony Taylor, Bobby Williams, George Lewis, Cliff Helfrich, Eric Carranza, Don Han, Ramachand Bhat and Jamin Greenbaum.

The eight-sided, solar-powered craft will fly as close as 100 kilometers (62 miles) to each nucleus, at top speeds that could cover the 56 kilometers between Washington and Baltimore in two seconds. A five-layer dust shield of heavey Nextel and Kevlar fabric protects the compact probe from the comet dust and debris.

"Comets are the solar system's smallest bodies, but among its biggest mysteries," said Dr. Joseph Veverka, Contour's principal investigator from Cornell University, Ithaca, N.Y. "We believe they hold the most primitive materials in the solar system and that they played a role in shaping some of the planets, but we really have more ideas about comets than facts. Contour will change that by coming closer to a comet nucleus than any spacecraft ever has before and gathering detailed, comparative data on these dynamic objects."

Contour's four scientific instruments will take pictures and measure the chemical makeup of the nuclei while analyzing the surrounding gases and dust. Its main camera, the Contour Remote Imager/Spectrograph, will snap high-resolution digital images showing car-sized rocks and other features on the nucleus as small as 4 meters (about 13 feet) across. The camera will also search for chemical "fingerprints" on the surface, which would provide the first hard evidence of comet nuclei composition.

Encke has been seen from Earth more than any other comet; it's an "old" body that gives off relatively little gas and dust but remains more active than scientists expect for a comet that has passed close to the sun thousands of times. Schwassmann-Wachmann 3, on the other hand, was discovered just 70 years ago and recently split into several pieces, intriguing scientists with hopes that Contour might see fresh, unaltered surfaces and materials from inside the comet.

Contour is the sixth mission in NASA's Discovery Program of lower cost, scientifically focused exploration projects. Johns Hopkins University's Applied Physics Laboratory manages the mission, and also built the spacecraft and its two cameras. NASA's Goddard Space Flight Center provided Contour's neutral gas/ion mass spectrometer and von Hoerner & Sulger, GmbH, Schwetzingen, Germany, built the dust analyzer.

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