A Close-Up View Of An Asteroid Will Be Available ... No Rocket
Required
Sixteen robotic emissaries have been sent by the world's space
agencies to fly by some of the solar system's most intriguing and
nomadic occupants -- comets and asteroids. The data and imagery
collected on these deep-space missions of exploration have helped
redefine our understanding of how Earth and our part of the galaxy
came to be. But this fall, Mother Nature is giving scientists
around the world a close-up view of one of her good-sized space
rocks -- no rocket required.
"On November 8, asteroid 2005 YU55 will fly past Earth and at
its closest approach point will be about 325,000 kilometers
[201,700 miles] away," said Don Yeomans, manager of NASA's
Near-Earth Object Program Office at the Jet Propulsion Laboratory
in Pasadena, CA. "This asteroid is about 400 meters [1,300 feet]
wide – the largest space rock we have identified that will
come this close until 2028."
Despite the relative proximity and size, Yeomans said, "YU55
poses no threat of an Earth collision over, at the very least, the
next 100 years. During its closest approach, its gravitational
effect on the Earth will be so miniscule as to be immeasurable. It
will not affect the tides or anything else."
Then why all the hubbub for a space rock a little bit wider than
an aircraft carrier? After all, scientists estimate that asteroids
the size of YU55 come this close about every 25 years. "While
near-Earth objects of this size have flown within a lunar distance
in the past, we did not have the foreknowledge and technology to
take advantage of the opportunity," said Barbara Wilson, a
scientist at JPL. "When it flies past, it should be a great
opportunity for science instruments on the ground to get a good
look."
YU55 NASA Image
2005 YU55 was discovered in December 2005 by Robert McMillan,
head of the NASA-funded Spacewatch Program at the University of
Arizona, Tucson. The space rock has been in astronomers' crosshairs
before. In April 2010, Mike Nolan and colleagues at the Arecibo
Observatory in Puerto Rico generated some ghostly images of 2005
YU55 when the asteroid was about 2.3 million kilometers (1.5
million miles) from Earth.
"The best resolution of the radar images was 7.5 meters [25
feet] per pixel," said JPL radar astronomer Lance Benner. "When
2005 YU55 returns this fall, we intend to image it at 4-meter
resolution with our recently upgraded equipment at the Deep Space
Network at Goldstone, CA. Plus, the asteroid will be seven times
closer. We're expecting some very detailed radar images."
Radar astronomy employs the world's most massive dish-shaped
antennas. The antennas beam directed microwave signals at their
celestial targets -- which can be as close as our moon and as far
away as the moons of Saturn. These signals bounce off the target,
and the resulting "echo" is collected and precisely collated to
create radar images, which can be used to reconstruct detailed
three-dimensional models of the object. This defines its rotation
precisely and gives scientists a good idea of the object's surface
roughness. They can even make out surface features. "Using the
Goldstone radar operating with the software and hardware upgrades,
the resulting images of YU55 could come in with resolution as fine
as 4 meters per pixel," said Benner. "We're talking about getting
down to the kind of surface detail you dream of when you have a
spacecraft fly by one of these targets."
At that resolution, JPL astronomers can see boulders and craters
on the surfaces of some asteroids, and establish if an asteroid has
a moon or two of its own. (Note: the 2010 Arecibo imaging of YU55
did not show any moons). But beyond the visually intriguing
surface, the data collected from Goldstone, Arecibo, and
ground-based optical and infrared telescopes are expected to detail
the mineral composition of the asteroid. "This is a C-type
asteroid, and those are thought to be representative of the
primordial materials from which our solar system was formed," said
Wilson. "This flyby will be an excellent opportunity to test how we
study, document and quantify which asteroids would be most
appropriate for a future human mission."
YU55 Predicted Trajectory NASA Image
Yeomans reiterated Wilson's view that the upcoming pass of
asteroid 2005 YU55 will be a positive event, which he describes as
an "opportunity for scientific discovery." Yeomans adds, "So stay
tuned. This is going to be fun."
The 70-meter (230-foot) Goldstone antenna in California's Mojave
Desert, part of NASA's Deep Space Network, is one of only two
facilities capable of imaging asteroids with radar. The other is
the National Science Foundation's 1,000-foot-diameter (305 meters)
Arecibo Observatory in Puerto Rico. The capabilities of the two
instruments are complementary. The Arecibo radar is about 20 times
more sensitive and can detect asteroids about twice as far away,
but because the main dish is stationary it can only see about
one-third of the sky. Goldstone is fully steerable and can see
about 80 percent of the accessible sky, so it can track objects
several times longer per day and can image asteroids at finer
spatial resolution. To date, Goldstone and Arecibo have observed
272 near-Earth asteroids and 14 comets with radar. JPL manages the
Goldstone Solar System Radar and the Deep Space Network for
NASA.
NASA detects, tracks and characterizes asteroids and comets
passing close to Earth using both ground- and space-based
telescopes. The Near-Earth Object Observations Program, commonly
called "Spaceguard," discovers these objects, characterizes a
subset of them, and plots their orbits to determine if any could be
potentially hazardous to our planet.