[meteorite-list] NEAR Shoemaker To Land On Eros On February 12

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:53 2004
Message-ID: <200101031807.KAA15420_at_zagami.jpl.nasa.gov>

http://www.space.com/scienceastronomy/solarsystem/near_landing_010103.html

Asteroid Landing Draws Near
By Leonard David
space.com
02 January 2001

WASHINGTON -- NASA has okayed a February 12 controlled descent of the Near
Earth Asteroid Rendezvous (NEAR) spacecraft onto the dust-laden, cratered
and boulder-strewn surface of Asteroid 433 Eros.

Ground controllers hope to fire spacecraft engines just prior to hitting the
space rock, perhaps allowing NEAR to briefly bounce off Eros, relay
last-minute science data, then plop itself down at a final resting spot.

The spectacularly successful NEAR Shoemaker probe has been orbiting Eros
since February 14, 2000. Since it began looping the tumbling space rock
almost a year ago -- at a range of high and low altitudes over Eros -- the
craft has amassed an asteroid photo gallery made up of 150,000 snapshots.

Later this month, NEAR is set to make daring flybys of Eros. Pictures
clicked during the maneuvers will show the greatest detail to date of
various features on the celestial hunk.

Downtime

"Everything continues to go swimmingly," said Robert Farquhar, NEAR mission
manager at the Johns Hopkins University Applied Physics Laboratory (APL) in
Laurel, Maryland. "Right now, NEAR is doing just fine," he told SPACE.com.

APL designed, built and is managing the NEAR mission for NASA.

Now being orchestrated is a progression of low-altitude flybys of Eros by
NEAR.

The spacecraft is set to zoom down between January 24 and 28, skimming over
the ends of the asteroid as it somersaults through space. NEAR may get as
close as about 1.6 miles (2.5 kilometers) above the asteroid's surface,
Farquhar said.

Last October, NEAR whisked by Eros at approximately 3 miles (5.3 kilometers)
above its surface, shooting over the asteroid at about 14 miles per hour (6
meters per second).

"What we have seen so far in the low orbits has merely whetted our appetite
for more," said Andrew Cheng, NEAR project scientist at APL. "We went up
close to have a better look at the surface than ever before, but we now see
things we do not understand, and we need more information," Cheng said.

Swoop and bounce

NEAR's finale on February 12, swooping down and striking Eros, should give
scientists photos that are 10 times better in resolution than anything
received. Images from only 1,640 feet (500 meters) above the asteroid's
surface are expected.

By firing NEAR's rocket engines just before making asteroid contact, at a
speed of 7 miles per hour (3 meters per second), the craft may hit, then
bounce off Eros. Spacecraft cameras are to be busy during the risky
controlled landing, the world's first touchdown on an asteroid.

"But the uncertainty is pretty large. Who knows what NEAR will do," Farquhar
said. "Even if it's a crash landing...it's a first landing," he said.

NEAR was not built to be a lander. The spacecraft's set of delicate solar
arrays and other hardware will likely succumb to any hard-hitting arrival.

Surface surprises

Scott Murchie, NEAR science team member at APL, said that landing on Eros is
gravy, contrasted to the rich bounty of data already gleaned.

"To be honest, with 150,000 images, nobody has had the chance to look at all
of them in detail. We're constantly going back and discovering interesting
details in images that we've taken months ago," Murchie said.

That in-depth survey of Eros has revealed numbers of surprises.

"One thing we've found is that the surface layer is unexpectedly complex,"
Murchie said. That surface covering, called regolith, is not dotted with as
many smaller craters as expected, he said.

Furthermore, the regolith appears relatively mobile, Murchie said, moving
about like a fluid and has "ponded" in certain areas. "So there's a
complicated geological story in the very small-scale surface features," he
said.

For Cheng, having more mysteries than answers simply means more work ahead.

"Perhaps it will not be us, but some future scientists, who will unravel
some of the mysteries we are studying. In any case, we are working hard to
understand the surface of Eros," Cheng said.
Received on Wed 03 Jan 2001 01:07:59 PM PST