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NEAR aborts asteroid rendezvous, will try again in May 2000



For Immediate Release, December 22, 1998

Helen Worth
The Johns Hopkins University
Applied Physics Laboratory
Laurel, Md. 20723

Doug Isbell
NASA Headquarters
Washington, D.C.


NEAR Spacecraft to Fly by Asteroid Eros on Dec. 23; Rendezvous 
with Eros in 2000
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A Dec. 20 spacecraft abort of the initial rendezvous burn of the 
Near Earth Asteroid Rendezvous (NEAR) spacecraft has resulted in 
a postponement of NEAR's orbit of asteroid 433 Eros, originally 
scheduled for Jan. 10, 1999. However, a flyby of the asteroid is
planned for Dec. 23, 1998, at 1:43 p.m. EST, that will provide 
valuable information for its later study.

"While the engine burn abort was unfortunate, we still expect to 
accomplish the rendezvous objectives, but at a later date," says 
NEAR Mission Manager, Dr. Robert W. Farquhar, of The Johns Hopkins 
University Applied Physics Laboratory, which manages the NASA 
mission. "We expect that the later rendezvous date will not
diminished the overall science return."

During the Dec. 23, 1998, flyby, scientists will gain a preview 
look at the asteroid and gain a global perspective that will 
provide important information in planning an orbit insertion. 
Mission designers are now expecting the rendezvous will take 
place by May 2000. Data obtained from the flyby will help determine 
the shape and size of the asteroid and if it has any moons.

The rescheduling of the NEAR mission was made necessary by the 
abort of a planned 20-minute engine burn on Dec. 20, 1998. The 
spacecraft aborted just seconds after initiation of the 
bipropellant burn, causing communications with the spacecraft 
to be lost for about 27 hours. Contact was reestablished early 
Dec. 22, after NASA's Deep Space Network locked onto a radio
signal from the NEAR spacecraft at about 8 p.m. EST, on Dec. 21.

Responding to a command from the Mission Operations Center, NEAR 
started downloading stored data early Dec. 22, which the mission 
team has been analyzing to determine the cause of the abort and 
why the spacecraft lost attitude control.

"We've looked at the data and we believe there has been no damage 
to the spacecraft or the propulsion system," says spacecraft 
systems engineer, Andrew G. Santo. "Our fault protection software 
identified the problem and switched NEAR to a safe mode. 
Essentially, it worked as designed."

During the Dec. 23 flyby NEAR will take approximately 500 images 
from as close as 4,100 kilometers (2,500 miles). Although the 
images will be of lower resolution than those taken June 27, 1997, 
during the flyby of asteroid 253 Mathilde, they will provide 
scientists with important information about the asteroid.

NEAR will then travel in an orbit around the sun that nearly 
matches that of Eros. In May 2000, the spacecraft and Eros will 
meet, making it possible to insert NEAR into orbit around the 
asteroid.

NEAR was launched Feb. 17, 1996 as the first launch of NASA's 
Discovery Program. Updates of mission activities and science 
returns will be posted on the Web site (http://near.jhuapl.edu) 
and on the NEAR mission hot line: (240) 228-5413.

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