Dates: September 3 through 6, 2002

Venue: Hyatt in Arlington, Virginia

Estimated Registration Fee: $150

Background Rationale and Goals for the Workshop

One hundred years is approximately the time scale for a 10% probability of
an Earth impact by a 100-meter sized near-Earth asteroid, one capable of
causing substantial regional disruption or destruction of societal

This is also the estimated time (~ 70 years) necessary to assure the
development of an appropriate mitigation technology and learn how to apply
it to an Earth threatening object (Belton et al, 2001).

These timescales are similar to the typical lifetime of a family from birth
through the death of grandchildren, and can be expected to be of particular
interest to contemporary society.

This confluence of timescales gives present urgency and special interest to
consideration of the scientific foundations on which near-Earth object (NEO)
collision avoidance and impact mitigation technologies must be based.

Programs for the detection of possible impactors are well in hand, and ideas
abound on how to apply the energy required to either disrupt or deflect an
incoming impactor (Hazards due to Comets & Asteroids, T. Gehrels, Ed.,
1994). Yet little published work exists to address the detailed scientific
and technical requirements for avoidance and mitigation technologies, and
whether an adequate knowledge base exists.

The need for space exploration of NEOs is widely recognized (e.g. in the
Spaceguard Survey report, Morrison, 1992; Space Surveillance, Asteroids and
Comets, and Space Debris, USAF Science Advisory Board report, 1997). More
recently, a UK Task Force on NEOs (Atkinson, 2001) recommends that an
international approach be considered that employs a coordinated set of
rendezvous missions based on inexpensive micro-satellite technology.

Even with the publication of such recommendations it is not clear, from what
has been published, that they are offered on a secure scientific and
technical basis. For example, micro-satellite spacecraft do have an
important role to play in the future scientific exploration of NEOs. Yet for
impact mitigation or collision avoidance technologies to succeed, a high
priority must be placed on scientific investigations intimately associated
with the deep interior structure and special material properties of these

Beyond revealing fundamental clues to the origins of planets, knowledge of
the deep interior structure of asteroids and comets is a requirement if one
means to apply whole-body forces to them and achieve predictable results.

To measure and characterize the needed properties encompassing mass, mass
distribution, material strengths, internal structure, shape, and spin state
(Huebner and Greenberg, 2002), novel kinds of spacecraft investigations will
be required. Locally, drilling and digging from the surface can provide some
of these data, but will probably be restricted to a limited depth. Globally,
radio and seismic wave experiments with active sources analogous to those
used in terrestrial exploration may be necessary. This will require the
development of whole new encounter technologies, and may lead to new
mitigation strategies as well.

This workshop will review what is known about the physics and chemistry of
the interiors of small cometary nuclei and asteroids with the purpose of
attaining a geophysical understanding of asteroids and comets in near-Earth
space. In addition, the workshop will work towards the following specific

  • Determination of the scientific requirements for those collision avoidance
    and impact mitigation technologies that are considered viable. This includes
    identification of measurements that are needed and the accuracy that should
    be attained.

  • Determination of what mission models and instrumentation developments are
    needed to make these measurements.

  • Construction of a mission and research roadmap for achieving an adequate
    level of knowledge on which to base the future development of practical and
    reliable collision avoidance and impact mitigation systems.


    Atkinson, H. 2001. UK Task Force on Near-Earth Objects. This report is best
    acquired through its web page:

    Belton, M.J.S., E. Asphaug, W. Huebner, and D. Yeomans 2001. Scientific
    requirements for NEO Impact Mitigation. Presented at Asteroids 2001 meeting,
    Palermo, Sicily.

    Hazards due to Comets and Asteroids 1994. Edited by Tom Gehrels, University
    of Arizona Press.

    Huebner, W.F., and J.M. Greenberg 2002. Erice Workshop Summary on Physical
    and Chemical Properties of Potential Earth Impactors, Meteoritics and
    Planetary Science, In Press.

    The Spaceguard Survey: Report of the NASA International Near-Earth-Object
    Detection Workshop 1992. Edited by David Morrison. Pasadena, CA: Jet
    Propulsion Laboratory.

    USAF Scientific Advisory Board 1997. Space Surveillance, Asteroids, and
    Comets, and Space Debris, Vol 1, Space Surveillance, SAB-TR-9604.

    Inquiries and suggestions to: Nalin Samarasinha

    NOAO is operated by the Association of Universities for Research in
    Astronomy (AURA), Inc. under cooperative agreement with the National Science
    Foundation. The USGP represents U.S. scientific, technical, and
    instrumentation interests in the international community of the Gemini
    project. The USGP is a division of the National Optical Astronomy
    Observatories (NOAO). Last updated 20 March, 2002.