NEAR-Shoemaker was the first spacecraft to orbit and (though this was not originally planned)
to land on an asteroid – Eros.
Built and operated by the Applied Physics Laboratory at Johns Hopkins University,
the probe was originally known simply as NEAR (Near-Earth Asteroid Rendezvous),
but was renamed NEAR-Shoemaker in memory of the American geologist Eugene
Shoemaker (1928-1997). It was the inaugural mission in NASA's Discovery
Program and the first probe powered by solar cells to operate beyond
the orbit of Mars.
On June 27, 1997, NEAR-Shoemaker flew by the asteroid 253
Mathilde at a distance of 1,200 kilometers and found it to be composed of extremely
dark material with many large impact craters, including one about 9 kilometers deep.
A deep-space maneuver in July 1997 brought the probe back around Earth on
January 23, 1998, for a gravity assist that put the spacecraft on course for its rendezvous with the Manhattan-sized
asteroid 433 Eros.
NEAR's instruments included a multispectral imager, a telescope with a CCD
(charge-coupled device) array to determine the size, shape, and spin characteristics
of the asteroid and to map its the surface; an X-ray/gamma-ray spectrometer
to determine the surface/near-surface elemental composition; a near-infrared
spectrometer to map the mineralogical composition; a magnetometer to measure
the magnetic field of Eros; and a laser altimeter to measure the distance
between the spacecraft and the asteroid's surface.
NEAR entered an orbit of 323 × 370 kilometers around Eros on February 14, 2000,
then moved to gradually smaller orbits over the next year or so, returning
a total of 160,000 images. During the final days of its mission, NEAR maneuvered
to within 24 kilometers and then, against all the odds, became the first spacecraft
actually to land on an asteroid. NEAR-Shoemaker was only designed to orbit
Eros. But with all of its objectives fulfilled, it was decided to try to
bring the craft in for what mission controllers called a "controlled
crash". In the final moments before it landed on February 12, 2001,
NEAR returned pictures showing surface details as small as a few tens of
cm across. Finally, in one of the great moments of space exploration, the
probe touched down so smoothly that its radio beacon continued to send out
a signal from its new home.
|NEAR-Shoemaker about to touch down
||Feb. 17, 1996
||2.8 × 1.7 m
||818 kg (total), 55 kg (science payload)
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