Like the massive white whale in Herman Melville's 1851 classic "Moby Dick," comets have long been considered swift, elusive harbingers of change. So it should be of little surprise that one of the best ways for scientists to study the mysteries of comets is to harpoon one.
The European Space Agency's Rosetta spacecraft is scheduled to lift off on Feb. 26, 2004, at 2:16 am Eastern time, from the Kourou spaceport in French Guiana, on the northeastern coast of South America. The launch will be the beginning of a ten-and-a-half year odyssey to comet Churyumov-Gerasimenko that includes flybys of Mars (2007) and the Earth (2005, 2007 and 2009).
Among the instruments aboard the Rosetta spacecraft are three instruments funded by NASA and a key component of a fourth. The NASA instruments will examine Churyumov- Gerasimenko from the orbiter.
"This comet has only about three-hundred-thousandths the gravity of Earth," said Dr. Claudia Alexander, project scientist for the U.S. role in the mission, from NASA's Jet Propulsion Laboratory Pasadena, Calif. "The Rosetta spacecraft will be able to make observations from as close as 2 kilometers (1.2 miles). The data from our state-of-the- art instruments will be amazing," she added.
Rosetta will reach Churyumov-Gerasimenko, a four-kilometer- diameter (2.5-mile) comet, in May 2014. When this rendezvous occurs, Churyumov-Gerasimenko will be about three times as far from the sun as Earth is. Over the next 18 months Rosetta will study how the comet changes as it moves closer to the sun. In November 2014, Rosetta will drop its experiment-laden, harpoon-firing lander on Churyumov- Gerasimenko's icy nucleus.
"What you have to understand is that comets are primordial remnants of the early solar system," explained Dr. Paul Weissman of JPL. "They are the keys to understanding the way the whole solar system, our Earth, and how even we came into being. And with Rosetta we will be able to observe, study and analyze this primordial material up close for more than a year," he said.
JPL supplied the Microwave Instrument for Rosetta Orbiter, the first of its type on any interplanetary mission. This instrument can reveal the abundances of selected gases, their temperatures, the speed at which they are coming off the nucleus, and the temperature of the nucleus. Scientists will use the instrument to monitor changes in how vapors are released from the nucleus as the coma and tail grow. They will be studying water, carbon monoxide, ammonia and methanol, four of the most abundant gases from comets. Dr. Samuel Gulkis of JPL's Earth and Space Sciences Division is principal investigator.
The Southwest Research Institute, based in San Antonio, supplied two NASA instruments for Rosetta. One is an imaging telescope/spectrometer capable of analyzing the composition both of gases released by the comet and of the comet's surface. A goal of scientists using the instrument is to learn about the temperatures at which comets form and evolve, by determining the relative abundance of noble gases, such as helium, neon and argon. Principal investigator for the ultraviolet instrument is Dr. Alan Stern of the institute's Space Studies Department in Bolder, Colo.
Dr. James Burch, of the Institute's Instrumentation and Space Research Division, San Antonio, is principal investigator for Rosetta's Ion and Electron Spectrometer. This device will measure the environment of charged particles surrounding comet Churyumov-Gerasimenko. It will also study the interaction between that environment and the solar wind of charged particles speeding outward from the Sun.
Key electronics for a fourth instrument, the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, have been supplied by Lockheed Martin Advanced Technology Center, Palo Alto, Calif. This instrument will examine gases surrounding the comet.
JPL, a division of the California Institute of Technology in Pasadena, manages the microwave instrument for NASA's Office of Space Science, Washington, D.C.
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