[meteorite-list] Asteroid 2007 VK184 Eliminated as Impact Risk to Earth
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 2 Apr 2014 17:00:06 -0700 (PDT)
Asteroid 2007 VK184 Eliminated as Impact Risk to Earth
NASA/JPL Near-Earth Object Program Office
April 2, 2014
Recent observations have removed from NASA's asteroid impact hazard list
the near-Earth object (NEO) known to pose the most significant risk of
Earth impact over the next 100 years.
2007 VK184, an asteroid estimated to be roughly 130 meters in size, has
been on NASA's Impact Risk Page maintained by the NEO Program Office at
the Jet Propulsion Laboratory (JPL) for several years, with an estimated
1-in-1800 chance of impacting Earth in June 2048. This predicted risk
translates to a rating of 1 on the 10-point Torino Impact Hazard Scale.
In recent months, 2007 VK184 has been the only known NEO with a non-zero
Torino Scale rating.
2007 VK184 was discovered in November 2007 by the NASA-funded Catalina
Sky Survey (CSS) at the University of Arizona and tracked by the CSS and
other stations for two months before moving beyond view of ground based
telescopes in January 2008.
But in the early morning hours of March 26 and 27, 2014, Dr. David
Tholen of the University of Hawaii sighted 2007 VK184 once again. Using
the 3.6-meter-diameter Canada-France-Hawaii Telescope at the Mauna Kea
Observatories in Hawaii, he was able to detect and track the asteroid.
Because it had not been observed for almost six years, its predicted
position was only approximate. Nonetheless, Dr. Tholen was able to find
it within the predicted search region, which is called a "recovery." He
measured the asteroid's position and movement relative to the background
of stars, and forwarded his tracking data to the Minor Planet Center
(MPC) in Cambridge, Massachusetts, the central node for the global NEO
Dr. Tholen said, "Although the asteroid will be closer to Earth and
brighter in May, I made the recovery attempt in March because I didn't
want the position uncertainty to grow so much that it would force a
time-consuming search of much more of the sky. The trade-off was
increased exposure time to detect such a faint, distant object. Greater
atmospheric turbulence on March 26 blurred the images of the asteroid
enough to make the detection questionable, but the March 27 images were
much better and confirmed the recovery."
The "Sentry" asteroid monitoring system at JPL automatically retrieved
the new observations of 2007 VK184 from the MPC database, updated the
orbit for the object, and computed a new impact hazard assessment. This
new work shows that 2007 VK184 will pass no closer than 1.9 million
kilometers (1.2 million miles) from the Earth in June 2048, with no
closer encounters predicted for the foreseeable future. The NEO Program
Office removed 2007 VK184 from the Impact Risk Page about three hours
after receiving Dr. Tholen's observations from the MPC.
"While these new observations of 2007 VK184 were challenging for Dave
Tholen to obtain, they were reported quickly, and the global,
distributed NEO impact hazard monitoring system worked smoothly to
provide the all-clear for this object," said Dr. Steven Chesley of the
NEO Program Office at JPL.
NASA's NEO Program supports and monitors this process at every stage.
The Program funds and oversees the efforts of the CSS, the JPL NEO
Program Office, the MPC, and Dr. Tholen.
JPL's Sentry is an automated monitoring system that continually scans
the most current catalog of known asteroids and predicts potential
hazards of impacts with Earth over the next 100 years. As additional
observations become available, objects will be removed from Sentry's
Impact Risk Page when sufficient data become available to eliminate any
potential for impact in the projected future. According to the Torino
Impact Hazard Scale, developed and used by NEO observers to assess
potential impact risks, a rating of 1 indicates a predicted event that
"merits careful monitoring," and a rating of zero indicates the
predicted event has "no likely consequences."
Objects typically appear on the Sentry Impact Risk Page because a
limited number of available observations may indicate a potential hazard
of impact with Earth but do not provide astronomers enough information
to precisely define their orbital movements. Whenever a newly discovered
NEO is posted on the Sentry Impact Risk Page, the most likely outcome is
that the object will eventually be removed as new observations become
available, the object's orbit is more precisely known, and its future
motion is more tightly constrained. NASA's NEO Program Office at JPL,
which operates Sentry, receives asteroid observations and orbit
predictions daily from the MPC. Once an asteroid is classified as a
near-Earth object, the Sentry system automatically calculates orbit
updates for it as new data become available.
NASA's Near-Earth Object Observation (NEOO) Program, located in the
Planetary Science Division of the Science Mission Directorate at NASA
Headquarters in Washington, D.C., is responsible for finding, tracking,
and characterizing near-Earth objects (NEOs) - asteroids and comets
whose orbits periodically bring them close to Earth. The NEOO Program
sponsors internal NASA and external research projects. The Jet
Propulsion Laboratory (JPL) in Pasadena, California, manages a NEO
Program Office for the Headquarters' NEOO Program and conducts a number
of NASA-sponsored NEO projects.
"Asteroid 2007 VK184 is another case study on how our system works,"
said Lindley Johnson, NASA's NEO Programs Executive at NASA
Headquarters. "We find them, track them, learn as much as we can about
those found to be of special interest - an impact hazard or a space
mission destination - and we predict and monitor their movement in the
inner solar system until we know they are of no more concern."
In conducting its work, the NEOO Program collaborates with other U.S.
government agencies, other national and international agencies, and
professional and amateur astronomers around the world. For example, NASA
works closely with the Federal Emergency Management Administration and
other federal government departments and agencies on NEO impact warning,
mitigation and response planning. The Program is responsible for
facilitating communications between the astronomical community, the
federal government and the public should any impact threat by an NEO be
NASA/JPL Near-Earth Object Program Office
Sentry Impact Risk
Catalina Sky Survey
Minor Planet Center
Received on Wed 02 Apr 2014 08:00:06 PM PDT