[meteorite-list] Asteroid 1998 WT24 Looks Even Better Second Time Around

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=4800

Asteroid Looks Even Better Second Time Around
Jet Propulsion Laboratory
December 17, 2015

[Images]
On the left is a radar image of asteroid 1998 WT24 taken in December 2001 
by scientists using NASA's the 230-foot (70-meter) DSS-14 antenna at Goldstone, 
California. Image credit:NASA/JPL-Caltech/GSSR/NRAO/AUI/NSF 

Asteroid 1998 WT24 safely flew past Earth on Dec. 11 at a distance of 
about 2.6 million miles (4.2 million kilometers, 11 lunar distances). 
During its flyby, NASA scientists used the 230-foot (70-meter) DSS-14 
antenna at Goldstone, California, to probe it with microwave transmissions. 
Using this technique, they created the highest-resolution radar images 
of the asteroid.


This is the second time asteroid 1998 WT24 has been in the sights of NASA's 
solar system radar. In December of 2001, Goldstone obtained the first 
radar images of 1998 WT24 (http://neo.jpl.nasa.gov/images/1998wt24.html), 
which revealed that the asteroid was about 1,300 feet (400 meters) in 
diameter and shaped like a Russet potato. The radar images from 2001 had 
a resolution of about 60 feet (19 meters) per pixel.

The new radar images achieve a spatial resolution as fine as 25 feet (7.5 
meters) per pixel. They were obtained using the same DSS-14 antenna at 
Goldstone to transmit high-power microwaves toward the asteroid. However, 
this time, the radar echoes bounced off the asteroid were received by 
the National Radio Astronomy Observatory's 100-meter (330-foot) Green 
Bank Telescope in West Virginia.

"With this upgraded resolution we can see the asteroid's ridges and concavities 
in much greater detail," said Shantanu Naidu, a postdoctoral researcher 
at NASA's Jet Propulsion Laboratory in Pasadena, California, who works 
with the radar team and set up the observing plan for the asteroid's flyby. 
"One or two other radar bright features that could be outcrops on the 
surface are also visible."

The next visit of asteroid 1998 WT24 to Earth's neighborhood will be on 
Nov. 11, 2018, when it will make a distant pass at about 12.5-million 
miles (52 lunar distances).

Naidu noted JPL's asteroid radar team is also preparing to observe asteroid 
2003 SD220, which will make its closest approach on Dec. 24 at about 28 
lunar distances.

"From optical observations, we know it could be anything between a few 
hundred meters and a few kilometers wide and that it is on NASA's list 
as a potential human-accessible target, said Naidu. "But that is about 
it. Using radar, we should be able to see the shape of the object. For 
me, that is what makes this job so exciting. Every time we observe something, 
we are seeing something nobody has ever seen. We are making an unknown 
known, and as a scientist what can be better than that?"

Radar is a powerful technique for studying an asteroid's size, shape, 
rotation, surface features and surface roughness, and for improving the 
calculation of asteroid orbits. Radar measurements of asteroid distances 
and velocities often enable computation of asteroid orbits much further 
into the future than would be possible otherwise.

NASA places a high priority on tracking asteroids and protecting our home 
planet from them. In fact, the U.S. has the most robust and productive 
survey and detection program for discovering near-Earth objects (NEOs). 
To date, U.S. assets have discovered about 98 percent of known NEOs.

In addition to the resources NASA puts into understanding asteroids, it 
also partners with other U.S. government agencies, university-based astronomers, 
and space science institutes across the country, often with grants, interagency 
transfers and other contracts from NASA, and also with international space 
agencies and institutions that are working to track and better understand 
these objects. In addition, NASA values the work of numerous highly skilled 
amateur astronomers, whose accurate observational data helps improve asteroid 
orbits after they are found.

JPL hosts the Center for Near-Earth Object Studies for NASA's Near-Earth 
Object Observations Program within the agency's Science Mission Directorate.

More information about asteroids and near-Earth objects is at these sites:

http://neo.jpl.nasa.gov

http://www.jpl.nasa.gov/asteroidwatch


Media Contact

DC Agle
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-9011
agle at jpl.nasa.gov 

Charles Blue
National Radio Astronomy Observatory
434.296.0314
cblue at nrao.edu 

2015-380