near_eros_001024 WASHINGTON -- With a huff and a puff of its thrusters, the Near Earth Asteroid Rendezvous (NEAR) spacecraft is diving toward asteroid Eros, on its way to a death-defying, low altitude flyby early Thursday morning of the space rock.
NEAR will begin its swan dive swoop over Eros today. In the early morning hours of Thursday, the probe will shoot across Eros at roughly 3 miles (5.3 kilometers) distance. The probes closest approach to Eros will be at 3:00 a.m. Eastern Daylight Time for about one-half hour, according to ground control estimates.
Linear features and grooves define a mysterious spiral pattern trending from upper right to lower left in this mosaic of NEAR spacecraft images of asteroid 433 Eros
.Onboard instruments are expected to snag a wealth of science data about the asteroid during some 5 hours of close-up inspection. The spacecraft will be scooting by Eros at about 14 miles per hour (6 meters per second).
"This will be the closest that any spacecraft will have gone to a celestial body without actually landing on it," said Andrew Cheng, NEAR project scientist at The Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland.
As NEAR zips by Eros, while the pictures of the body are sure to be spectacular, the probes X-Ray/Gamma-Ray Spectrometer (XGRS) is expected to glean key data. It will measure and map abundances of several dozen key elements that make up Eros, Cheng told SPACE.com.
Less than routine
NEAR will zoom by Eros at about the same altitude as that of a commuter airplane on Earth.
The asteroid is tumbling end-over-end in its orbit. So timing is everything.
At APL -- which built and manages the spacecraft for NASA -- ground controllers are at the ready to carry out the less-than-routine maneuver.
"Its certainly doable. We wouldnt do anything to put the spacecraft at risk," said APLs Louise Prockter, member of the NEAR imaging team. "Although we are well over half-way through the mission, theres still a lot more we want to accomplish. We wouldnt attempt this flyby if we werent absolutely confident that it was going to work," she said.
~
Spectacular look-see
Almost an order of magnitude higher resolution is expected from NEARs camera as it slips over the asteroid. "Were going to be able to see detail that we havent even begun to imagine we can see," Prockter said.
The exact path and features that NEAR will survey is uncertain. "The whole of Eros is interesting. So whatever we can look at...were going to be pretty happy," Prockter said.
Map shows topography of Eros' gravity field. Objects on Eros would tend to move downhill from red areas to blue or green areas.
Prockter said that the close-up pictures might help answer several questions, such as does Eros have a regolith - a layer of rock and dirt spread over the asteroids surface. If the regolith is there, the images may help determine just how deep is that covering, she said.
Also, the up-close-and-personal peek at Eros should enable scientists to count very, very small craters. That would give them a better idea about the age of certain regions on the asteroid, Prockter said.
Dont say the "L" word
After making its slow speed flyover of Eros, NEAR will then sweep back up toward a 125 mile (200 kilometer) orbit around the asteroid. It will stay there for the next month. In December, the craft starts a set of lower and lower orbits, gathering science data about Eros from the various altitudes.
The mission is set to end in February 2001 - a full year after NEAR Shoemaker started its looping of the asteroid.
NASA has given NEAR controllers the go-ahead to attempt a "controlled descent" of the spacecraft, alighting it atop Eros on February 12.
Controlled descent is a more politically-correct euphemism for landing.
"Its never been done," said Robert Farquhar, APLs NEAR mission manager. "Well be thrusting all the way down," he said.
Staggering images are expected from NEAR as it drops toward the asteroids rocky surface. Because the camera is, in essence, a telescope, pictures of the surface will become blurred as NEAR moves closer and closer to its final resting spot. Images of the distant horizon, however, are likely to be relayed back to Earth.
Could NEAR survive its touchdown?
"Its conceivable. But I dont know how likely that is," APLs Cheng said.
advertisement
