NASA Spacecraft 'Lands' on Asteroid
The Shoemaker spacecraft made an unprecedented
"landing" today on an asteroid the size of the San
Fernando Valley, then bounced about 40 stories high
before settling down again, a JPL navigation engineer
said.
Jim Miller, the deputy navigation team chief, admitted
later he was somewhat surprised that the "stunt" could
be done.
"At the beginning (of the Near Earth Asteroid
Rendezvous project), when we started planning this, I
came out and said" the chances for success were about
one in 100, he said, but by today that was down to
50-50.
"I can't think of anyone that was really confident
that it was going to work," he said. "We were very
much surprised by how soft it landed."
Originally expected to come down on Valentine's Day,
the schoolbus-sized Shoemaker made impact on 433 Eros
two days--and a couple of minutes--early, and 800 feet
or so from where the engineers predicted. It bounced
about 100 meters--or 390 feet--high, he said. ¸U
b…¹'o'?the spacecraft safely on Eros at about 12:02
(p.m.)," Miller said, "and it's continuing to
transmit." Engineers were hoping to re- establish the
ability to contact the unmanned spacecraft on the
asteroid about 196 million miles from Earth.
Because of the near-absence of gravity on the
asteroid, the spacecraft only weighed about 2 pounds
at impact--and was going about 5 mph.
"It more or less crashed on to the surface" of 433
Eros, Miller said, though engineers in Maryland fired
the spacecraft's retro-rockets four times as the
Shoemaker fell toward the asteroid's surface to slow
down the descent.
He said Shoemaker was sending back a picture when it
hit the surface.
Miller said he informed his colleagues at one point
that they could celebrate and applause broke out.
He said the spacecraft launched in 1996 had been
orbiting for about a year, and has sent back thousands
of pictures since then, including some today of the
crater-pocked and boulder-strewn asteroid.
The primary goal of the spacecraft's "controlled
descent" to the surface was to gather images of Eros.
Mission managers from the Johns Hopkins University
Applied Physics Lab in Laurel, Md., brought the
spaceship in for the landing, firing its engines over
a four-hour period.
The spacecraft dropped out of an orbit some 22 miles
above 433 Eros and made its descent toward the
21-mile-long asteroid. On the way down, it recorded
images that should help scientists better understand
the asteroid's origins.
"We know that Eros is a solid body of uniform
composition, made of material that is probably older
than the Earth," said Andrew Cheng of the Applied
Physics Lab at Johns Hopkins, where the spacecraft was
built.
"But we also found many other things we didn't expect
to see and have questions we didn't know to ask at the
start of the mission."
Scientists are particularly interested in the
asteroid's "saddle" area, a 6-mile-wide depression
with patches of boulders, a relatively craterless
surface and patterns of grooves and ridges.
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