(Latest revision: 2001 December 20)

Position Statement

The IAU, recognizing its responsibility to encourage timely and
responsible communication with the public and the press concerning
possible impact hazards, has established the following procedures to
be available to the members of the astronomical community in case of
discovery and/or theoretical analysis leading to the prediction of

The accuracy of a prediction depends on both the observational data
and the computational methods used. The IAU encourages its members to
actively seek out and make available any observations that may help
refine the orbit of a potentially threatening NEA. In addition, the
following IAU review procedure of orbital computations and risk
estimates is available on a voluntary basis to all scientists
involved in any prediction of possible NEO impacts. This review
procedure is encouraged for any prediction that is at a level equal
to or greater than zero on the Palermo Technical Scale, a scale that
compares the impact probability of the predicted event to the hazard
posed by the background NEO population, taking into account the
estimated size of the object and the time interval until the
encounter. An object having the same or higher impact probability as
that of the background population will have a Palermo Technical Scale
value equal to or greater than zero. In most cases, such events will
fall at a value of 1 or higher on the 0-10 point Torino Scale, a
scale intended for public communication of impact hazard risks.

The procedure for technical review is as follows. Information leading
to an impact prediction, consisting of an evaluation of the case and
all data and computational details necessary to understand and
reproduce the studies carried out by the authors, should be
transmitted for confidential review to the chair of the IAU Working
Group for Near Earth Objects (WGNEO), the President of IAU Division
III, the General Secretary of the IAU, and the members of the NEO
Technical Review Team (see below), before any announcement and/or
written document on the subject be made public via any potentially
nonprivate communication medium, including the World Wide Web. The
individual members of the NEO Technical Review Committee shall review
the work for technical accuracy and shall communicate under most
circumstances within 72 hours the results of their reviews to the
chair of the WGNEO and directly to the authors of the report or

The authors of the work are encouraged to refer to this IAU review
and may quote this review if and when they choose to make a public
release of their conclusions. If the consensus of the above review
supports the conclusion that there is a significant impact risk
meriting an announcement by the IAU itself, such an announcement will
be posted on the IAU webpage http://www.iau.org/ for public access as
soon as possible after the information is released by the authors to
the public. If the review disagrees with the original analysis or if
there is not a consensus among the reviewers, the confidential
results of the review will be given to the authors so they can revise
or improve their work, as they see fit.

It is important to note that the WGNEO will review impact
probabilities and reach conclusions based on the best observational
information available at the time of the review. It is expected that
new data that may be obtained during the period of the review and/or
in the days, weeks, and months (in some cases years) that follow will
provide sufficient new information for new probability calculations
to be made. The most likely eventuality is that new calculations
based on additional new data will ultimately yield impact
probabilities that are effectively zero.

The news posted on the IAU webpage shall represent the official
position of the IAU; further information will be provided by the
WGNEO in case important updates become necessary. If so requested
officially (e.g., by NASA or ESA), the IAU will also inform the
responsible officials of relevant agencies of the results of the
WGNEO review.

The Review Team

The NEO technical review team consists of:

Paul Chodas: Paul.W.Chodas@jpl.nasa.gov

Andrea Milani: milani@dm.unipi.it

Karri Muinonen: Karri.Muinonen@Helsinki.Fi

Giovanni Valsecchi: giovanni@ias.rm.cnr.it

Don Yeomans: donald.k.yeomans@jpl.nasa.gov

In addition, information copies are requested to be sent to

David Morrison: dmorrison@arc.nasa.gov, Chair, WGNEO

Richard P. Binzel: rpb@mit.edu, Secretary, WGNEO

Mikhail Marov: marov@applmat.msk.su, President, IAU Division III

Brian G. Marsden: marsden@cfa.harvard.edu, Director, Minor Planet Center

Hans Rickman: hans@astro.uu.se, General Secretary, IAU

Andrea Carusi: carusi@ias.rm.cnr.it, Spaceguard Foundation

All the above agree to keep the prediction documentation
confidential, and to honor the right of the author(s) of the
discovery or prediction to publish the results and to make them
public, at their discretion, and in the manner they choose.

From the WGNEO webpage — http://web.mit.edu/rpb/wgneo/