> -----Original Message-----
> From: mpml@yahoogroups.com [mailto:mpml@yahoogroups.com] On
> Behalf Of Ron Baalke
> Sent: Wednesday, January 09, 2008 5:44 PM
> To: Minor Planet Mailing List
> Subject: {MPML} 2007 WD5 Mars Collision Effectively Ruled Out
> - Impact Odds now 1 in 10,000
>
>
> http://neo.jpl.nasa.gov/news/news156.html
>
> 2007 WD5 Mars Collision Effectively Ruled Out - Impact Odds
> now 1 in 10,000
> Steve Chesley, Paul Chodas and Don Yeomans
> NASA/JPL Near-Earth Object Program Office
> January 9, 2008
>
> Since our last update, we have received numerous tracking measurements
> of asteroid 2007 WD5 from four different observatories. These new data
> have led to a significant reduction in the position
> uncertainties during
> the asteroid's close approach to Mars on Jan. 30, 2008. As a
> result, the
> impact probability has dropped dramatically, to approximately
> 0.01% or 1
> in 10,000 odds, effectively ruling out the possible collision
> with Mars.
>
> Our best estimate now is that 2007 WD5 will pass about 26,000 km from
> the planet's center (about 7 Mars radii from the surface) at around
> 12:00 UTC (4:00 am PST) on Jan. 30th. With 99.7% confidence, the pass
> should be no closer than 4000 km from the surface.
>
> [Graphic]
> Updated Uncertainty Region for 2007 WD5 at encounter with
> Mars, shown as
> white dots. The thin white line is the orbit of Mars. The blue line
> traces the motion of the center of the uncertainty region,
> which is the
> most likely position of the asteroid. Image of 2007 WD5 from the
> University of Hawaii 2.2-meter telescope on Mauna Kea, Hawaii.
>
> [Image]
> Image of 2007 WD5 from the University of Hawaii 2.2-meter telescope on
> Mauna Kea, Hawaii. The circled dot is the asteroid. Other dots are
> artifacts from cosmic rays. The stars are trailed because the
> telescope
> is tracking the asteroid as it moves among the stars. (Credit: Tholen,
> Bernardi, Micheli with support from the National Science Foundation).
>
> The sequence of updates over the last few weeks has been
> typical of past
> potential impact scenarios, with the odds of impact initially surging
> and later plummeting towards zero. Early on, the uncertainty region is
> very large and the probability of impact is rather low. As the
> uncertainty narrows, but still includes the planet, the probability
> initially increases. But eventually, as in this case, the uncertainty
> region shrinks to the point that it no longer overlaps the planet, and
> the probability of impact begins a precipitous decline. This rise and
> fall of the computed hazard was most notably seen in Dec. 2004 when
> asteroid 99942 Apophis briefly reached a 2.7% chance of impact with
> Earth in April 2029. In every case, the height and the timing of the
> peak probability - and the subsequent decline - cannot be known until
> the uncertainty region has shrunk to the point where it no longer
> intersects the planet.
>
> NASA's Spaceguard Survey continues searching for Near-Earth Asteroids
> such as 2007 WD5, endeavoring to discover 90% of those larger
> than 1 km
> in size, a goal that should be met within the next few years. Each
> discovered asteroid is continually monitored for the possibility of
> impact. For 2007 WD5, these analyses show there is no possibility of
> impact with either Mars or Earth in the next century.
>
> This unfolding story and the present results have been made
> possible by
> the tracking efforts of many astronomers at several
> observatories around
> the world:
>
> * 2007 WD5 was discovered using the Mt. Lemmon 1.5-meter telescope
> by Andrea Boattini of the University of Arizona's Catalina Sky
> Survey, which is led by Steve Larson.
>
> * Follow-up from archival images taken by the 1.8-meter
> telescope on
> Kitt Peak in Arizona were provided by Terrence H. Brezzi of the
> University of Arizona's Spacewatch Project, which is
> led by Robert
> McMillan.
>
> * Andy Puckett of the Univ. of Alaska obtained pre-discovery
> measurements from archival images of the Sloan Digital Sky
> Survey?s 2.5-meter telescope on Apache Point, NM.
>
> * Bill Ryan of New Mexico Tech's Magdalena Ridge Observatory
> observed 2007 WD5 on several crucial nights, with
> critical support
> from university and observatory staff.
>
> * Observations from the 6.5-meter Multi-Mirror Telescope (MMT)
> Observatory in Arizona were provided by a team consisting of
> Holger Israel (Univ. Bonn), Matt Holman (Harvard/CfA), Steve
> Larson (Univ. Ariz.), Faith Vilas (MMTO), Cesar Fuentes
> (Harvard/CfA), David Trilling (Univ. Ariz.) and Maureen Conroy
> (Harvard/CfA).
>
> * The 3.5-meter telescope at the Calar Alto Observatory in Spain
> provided follow-up through a team consisting of Adriano Campo
> Bagatin (Univ. Alicante), Gilles Bergond (Calar Alto Obs.), Rene
> Duffard (Inst. de Astrofisica de Andalucia), Jose Luis Ortiz
> (Inst. de Astrofisica de Andalucia), Reiner Stoss (Obs.
> Astronomico de Mallorca and Astronomisches Rechen-Institut) and
> Javier Licandro (Inst. de Astrofisica de Canarias).
>
> * Fabrizio Bernardi, Marco Micheli and Dave Tholen of the Univ. of
> Hawaii Institute for Astronomy observed the asteroid at its
> faintest using the 2.2-meter UH telescope on Mauna Kea
> in Hawaii.
>
>
>
>
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