[meteorite-list] SENTRY - An Automatic Near-Earth Asteroid Collision Monitoring System

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:02:27 2004
Message-ID: <200203130108.RAA23170_at_zagami.jpl.nasa.gov>

SENTRY - An Automatic Near-Earth Asteroid Collision Monitoring System

NASA's Near-Earth Object Program Office (http://neo.jpl.nasa.gov)
announces the arrival of the Sentry automatic impact monitoring
system. In development for nearly two years, Sentry is a highly
automated, accurate, and robust system for continually updating the
orbits, future close Earth approaches, and Earth impact probabilities
for all Near-Earth Asteroids (NEAs).

When interpreting the Sentry Impact Risks Page
(http://neo.jpl.nasa.gov/risk/), where information on
known potential NEA impacts is posted, one must bear in mind that
an Earth collision by a sizable NEA is a very low probability event.
Objects normally appear on the Risks Page because their orbits can
bring them close to the Earth's orbit and the limited number of
available observations do not yet allow their trajectories to be
well-enough defined. In such cases, there may be a wide range of
possible future paths that can be fit to the existing observations,
sometimes including a few that can intersect the Earth.

Whenever a newly discovered NEA is posted on the Sentry Impact Risks
Page, by far the most likely outcome is that the object will eventually
be removed as new observations become available, the object's orbit is
improved, and its future motion is more tightly constrained. As a
result, several new NEAs each month may be listed on the Sentry Impact
Risks page, only to be removed shortly afterwards. This is a normal
process, completely expected. The removal of an object from the Impact
Risks page does not indicate that the object's risk was evaluated
mistakenly: the risk was real until additional observations showed
that it was not.

While completely independent, the Sentry system is meant to be
complementary to the NEODyS CLOMON impact monitoring system operated
in Pisa, Italy. Personnel from both the Sentry and NEODyS systems are
in constant communication, cross checking each other's results and
providing constructive feedback to continuously improve the efficiency,
accuracy, and robustness of both systems.

The Sentry system was developed largely by Drs. Steve Chesley and Alan
Chamberlin with significant technical help from Dr. Paul Chodas. Ron
Baalke provided our web site updates.

Donald K. Yeomans
Manager, NASA's Near-Earth Object Program Office
March 12, 2002
Received on Tue 12 Mar 2002 08:08:41 PM PST