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