February 15, 2001 -- 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.
For more information, visit the NEAR Web site at http://near.jhuapl.edu/
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