NEAR Shoemaker Gets New Lease on Life at Home on Asteroid

NASA’s NEAR Shoemaker spacecraft, the first spacecraft to
touch down and operate on the surface of an asteroid, will not
be immediately shut down after all, NASA officials announced
yesterday.

Brought to a successful landing on Feb. 12 with guidance
from the NEAR Shoemaker navigation team at NASA’s Jet
Propulsion Laboratory, Pasadena, Calif., the spacecraft’s
mission will be extended for up to 10 days to gather data from
a scientific instrument that could provide unprecedented
information about the surface and subsurface composition of
the asteroid Eros.

Three days after touchdown, NEAR Shoemaker is still in
communication with the NEAR team at Johns Hopkins University
Applied Physics Laboratory (APL) in Laurel, MD. Earlier this
week, the team sent commands to NEAR Shoemaker and guided the
robotic researcher to a gentle touchdown on a rock-strewn
plain on the asteroid. The spacecraft gently hit the surface
at 12:02 p.m. Pacific Standard Time (3:02 p.m. EST). It had
slowed to a gentle speed of between 1.5 and 1.8 meters per
second (less than 4 miles per hour) just before finally coming
to rest after a journey of 3.2 billion kilometers (2 billion
miles).

Mission operators say the touchdown may have been one of
the slowest planetary landings in history. They also have a
better picture of what happened in the moments after the
landing. What they originally thought was the spacecraft
bouncing may have been little more than short hop or “jiggle”
on the surface; the thrusters were still firing when the craft
hit the surface, but cut off on impact; and NEAR Shoemaker
came down only about 200 meters (650 feet) from the projected
landing site.

“It essentially confirmed that all the mathematical
models we proposed for a
controlled descent would work,” said Dr. Bobby Williams, NEAR
navigation team leader at the Jet Propulsion Laboratory. “You
never know if they’ll work until you test them, and this was
like our laboratory. The spacecraft did what we expected it to
do, and everyone’s real happy about that.”

On Tuesday, Feb. 13, the NEAR mission operations team
decided against another engine firing that could have lifted
the space probe off the asteroid’s surface. There were initial
concerns that it might be necessary to adjust the spacecraft’s
orientation in order to receive telemetry from the ground.
However, NEAR Shoemaker landed with a favorable orientation,
and there is no
problem with receiving information. Mission managers have
decided it is not necessary to move the spacecraft from its
resting place on the surface of Eros.

The spacecraft spent the last year in a close-orbit study
of asteroid 433 Eros, a near-Earth asteroid that is currently
196 million miles from Earth. During that time it collected 10
times more data than originally planned and completed all its
science goals before its descent to the asteroid.

Funding for the mission extension will come from the NEAR
Project.

The NEAR Shoemaker spacecraft’s historic soft landing on
asteroid 433 Eros Feb. 12 turned out to be a mission planner’s
dream — providing NEAR team members with more scientific and
engineering information than they ever expected from the
carefully designed series of descent maneuvers.

“We put the first priority on getting high-resolution
images of the surface and the second on putting the spacecraft
down safely — and we got both,” says NEAR Mission Director
Dr. Robert Farquhar of the Applied Physics Laboratory, which
manages the Near Earth Asteroid Rendezvous (NEAR) mission for
NASA. “This could not have worked out better.”

NEAR Shoemaker snapped 69 detailed pictures during the
final 5 kilometers (3 miles)
of its descent, the highest resolution images ever obtained of
an asteroid. The camera delivered clear pictures from as close
as 120 meters (about 400 feet) showing features as small as
one centimeter (one-third inch) across. The images also
included several things that piqued the curiosity of NEAR
scientists, such as fractured boulders, a football-field sized
crater filled
with dust, and a mysterious area where the surface appears to
have collapsed.

“These spectacular images have started to answer the many
questions we had
about Eros,” says Dr. Joseph Veverka, NEAR imaging team leader
from Cornell University in Ithaca, N.Y., “but they also
revealed new mysteries that we will explore for years to
come.”

NEAR Shoemaker launched on Feb. 17, 1996 — the first in
NASA’s Discovery
Program of low-cost, scientifically focused planetary missions
— and became the first spacecraft to orbit an asteroid on
Feb. 14, 2000. The car-sized spacecraft gathered 10 times more
data during its orbit than originally planned, and completed
all the mission’s science goals before Monday’s controlled
descent.

JPL is a division of the California Institute of
Technology in Pasadena.