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Subject: Историческое событие Replies: 11799 Date : 12 Feb 2001 14:23 GMT From : Анатолий Зайцев [AZ] (azet@mail.ru) To : All
Сегодня в 20:05 GMT будет впервые в истории произведена посадка космического зонда NEAR Шумейкер на астероид Эрос. См. сайт http://near.jhuapl.edu 2001 Feb 12 NEAR Team, Spacecraft Ready for Historic Controlled Descent to an Asteroid NASA's Near Earth Asteroid Rendezvous (NEAR) mission, the first to orbit an asteroid, attempts another deep-space first today with the NEAR Shoemaker spacecraft's controlled descent to the surface of 433 Eros. The main goal of the descent is to gather close-up pictures of the cratered, boulder-strewn surface of Eros, the 21-mile-long asteroid NEAR Shoemaker has orbited since Feb. 14, 2000. In its yearlong study NEAR Shoemaker compiled the most detailed profile yet of a small celestial body, collecting 10 times more data than originally planned. Now with the spacecraft nearly out of fuel and NEAR's science goals well exceeded, mission team members say the descent is a valuable opportunity to gather additional data. "This is a bonus," says NEAR Mission Director Dr. Robert Farquhar of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., which built NEAR Shoemaker and manages the mission for NASA. "The descent maneuvers are the most complicated we've ever tried, and because the spacecraft is an orbiter that wasn't designed to land, there is only the smallest chance it will survive on the surface of Eros. But this has never been done before, and the science and engineering data we hope to gather during the descent is worth the risk." NEAR Shoemaker's 4½-hour descent will begin at 10:31 a.m. Eastern time with a maneuver moving it out of a circular orbit 22 miles (35 kilometers) from the center of Eros. Mission operators at APL and navigators at NASA's Jet Propulsion Laboratory in Pasadena, Calif., will examine images taken after this maneuver to estimate the spacecraft's location and altitude, and set the timing on the craft for the final thruster firings. About three hours later, when NEAR Shoemaker reaches three miles (five kilometers) above the surface, it will start a series of four braking burns, ranging from three to six minutes each, set about 15 minutes apart. Designed to slow the spacecraft's approach to about 5 mph, it's the fastest succession of maneuvers NEAR has ever attempted. NEAR Shoemaker will approach Eros on its side, its outward-facing camera pointed down, snapping about two photos a minute. The spacecraft is headed for an area outside Himeros, the asteroid's distinctive six-mile (10-kilometer)-wide, saddle-shaped depression. "It's an exciting area geologically because we're on the edge of this large depression - which is probably a very large impact crater - and we'll be getting images of its interior as well as of the heavily cratered terrain on the outside," says NEAR imaging team member Mark Robinson of Northwestern University, Evanston, Ill. "This is a great opportunity to look at two very distinct terrains." The last clear pictures from the telescopic camera, taken from approximately 1,650 feet (500 meters), could show surface features as small as four inches (10 centimeters) across. After that, NEAR mission operators will use the blurring photos, range measurements from NEAR Shoemaker's laser ranging instrument, Doppler tracking and the eventual loss of signal to learn when NEAR Shoemaker touches down, predicted for 3:05 p.m. Eastern time. NEAR team members will listen for a beacon signal that would indicate NEAR Shoemaker has survived the descent and is operating on the surface. Deep Space Network antenna stations in Madrid, Spain, and Goldstone, Calif., will simultaneously cover the maneuvers as they happen more than 196 million miles (316 million kilometers) away. Data from the spacecraft will take between 17-18 minutes to reach the tracking stations on Earth. NEAR was the first in NASA's Discovery Program of low-cost, scientifically focused planetary missions. The car-sized NEAR Shoemaker spacecraft has since traveled nearly 2.3 billion miles (3.7 billion kilometers) since it launched from Cape Canaveral Air Station, Fla., on Feb. 17, 1996


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