Dave Tholen (IfA)

The University of Hawaii Aten Survey

The number of asteroids with Earth-crossing orbits that are large enough
to cause a global catastrophe, if one were to impact the Earth, is estimated
to be approximately 2000.  Various close approaches of asteroids to the
Earth, as well as the impact of comet Shoemaker-Levy 9 with Jupiter, have
led NASA to increase funding for near-Earth asteroid search efforts.
Existing search efforts have concentrated on the opposition region of the
sky, where low phase angles help to make near-Earth objects brighter and
therefore easier to detect.  Such a search strategy is heavily biased
against the discovery of objects with aphelion distances near 1 AU, yet
such objects can represent a relatively greater impact hazard, because
tangential orbits of low inclination spend a greater amount of time inside
the Earth's capture cross-section.  To find such objects requires observations
at solar elongations of less than approximately 90 deg, which is complicated
by limited viewing windows and higher phase angles.  During this talk, I will
discuss the work being done at IFA to tackle this aspect of the asteroid
hazard issue.