Feb 13, 2001

It's Not Over Yet!




Following one of the softest planetary landings in history, ground controllers have decided to extend NEAR Shoemaker's mission a little longer. Scientists hope to gather unique data from the very surface of asteroid Eros.


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February 14, 2001 -- One year after NASA's NEAR Shoemaker spacecraft went into orbit around asteroid 433 Eros, and two days after it actually landed on the space rock, mission planners say they aren't ready to turn off the spacecraft just yet.


The mission will be extended for as many as ten days to gather data from the spacecraft's gamma-ray spectrometer, a scientific instrument that could provide unprecedented information about the surface and subsurface composition of Eros.

Right: A digital artist's concept of NEAR Shoemaker's landing on asteroid 433 Eros. [more]

NEAR Shoemaker's historic soft landing on Eros has turned out to be a mission planner's dream. "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 Robert Farquhar of the Johns Hopkins University Applied Physics Laboratory, which manages the Near Earth Asteroid Rendezvous (NEAR) mission for NASA. "This could not have worked out better," he said.

Two days after a set of maneuvers brought it to the surface of Eros, NEAR Shoemaker is still communicating with the team at the Applied Physics Lab. The spacecraft gently touched down just after 3:01 p.m. EST on Monday, February 12th, ending a full year in orbit around the large space rock.


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Left: These images were captured by NEAR Shoemaker as it descended to the surface of Eros on February 12, 2001. The streaky lines at the bottom of the closest picture, taken at a range of 120 meters, indicate loss of signal as the spacecraft touched down on the asteroid during transmission. [more information]


Mission operators say the touchdown speed of less than 4 miles per hour (between 1.5 and 1.8 meters per second) 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 a short hop or "jiggle" on the surface; the thrusters were still firing when the craft hit the surface, but cut off on impact. NEAR Shoemaker came down only about 650 feet (200 meters) from the projected landing site.

"It essentially confirmed that all the mathematical models we proposed for a controlled descent would work," says Bobby Williams, NEAR navigation team leader at NASA's 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."

NEAR Shoemaker snapped 69 detailed pictures during the final three miles (five kilometers) of its descent, the highest resolution images ever obtained of an asteroid. The camera delivered clear pictures from as close as 394 feet (120 meters) showing features as small as one centimeter 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.


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"These spectacular images have started to answer the many questions we had about Eros," says Joe Veverka, NEAR's imaging team leader from Cornell University, N.Y., "but they also revealed new mysteries that we will explore for years to come."


Yesterday, the NEAR mission operations team decided against another engine firing that could have lifted the space probe off the asteroid's surface again.

Funding for the mission's extension will come from the NEAR project.

Above: The location of NEAR Shoemaker's landing site as viewed from an orbital altitude of 200 kilometers (124 miles). The landing site (at the tip of the arrow) is near the boundary of two distinctly different regions: To the south and east (above and to the left) lies older, cratered terrain, while to the north (down) is the saddle-shaped feature Himeros, whose lesser density of superimposed craters indicates relatively recent resurfacing by geologic processes. [more]



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

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Near Earth Asteroid Rendezvous mission - NEAR home page from Johns Hopkins University Applied Physics Laboratory

A Close Encounter with Asteroid Eros - Oct. 26, 2000 Science@NASA story: NASA's NEAR Shoemaker spacecraft swooped 3 miles above the surface of 433 Eros on Oct 26th, marking its closest-ever approach to the tumbling space rock.

Square Craters -- September 26, 2000 Science@NASA story: NASA's NEAR Shoemaker spacecraft has spotted square-shaped craters on asteroid Eros, a telltale sign of mysterious goings-on in the asteroid belt long ago.

Asteroids Have Seasons, Too - June 21, 2000 Science@NASA story: Later this week, the Sun will rise over the south pole of asteroid Eros, revealing unexplored terrain to the instruments on NASA's NEAR-Shoemaker spacecraft.



More Facts about Eros


Eros circles the Sun once every 1.76 Earth years. It spins on its axis once every 5.27 hours.[more]
Eros is about 21 by 8 by 8 miles (33 by 13 by 13 kilometers) in size. Its shape has been compared to a shoe, a battered boat, or a peanut. [more]
The gravity on Eros is very weak but enough to hold a spacecraft. A 100-pound (45-kilogram) object on Earth would weigh about 1 ounce on Eros. [more]
Eros is a "Near-Earth Asteroid" or NEA. Its next close approach will come in January 2012, when it will pass 0.178 AU from our planet. There is no chance of a collision.[More]


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