Asteroid Potential Impact Warnings
Chesley, S.R.; Chodas, P.W.
Jet Propulsion Laboratory

An inevitable consequence of asteroid search programs is that there are discoveries of asteroids that, for some period of time, will have a statistically significant chance of impact with the Earth. While it is very unlikely that any of these particular objects is actually on an collision course, an impact cannot be ruled out and so it is imperative that appropriate resources and analysis be applied to the situation. For almost a decade, these potential impact warnings have been routinely reported to the wider astronomical community as a part of ongoing asteroid impact monitoring programs.

If a recently discovered asteroid is, in fact, on course for a very close approach to the Earth then it will often carry some potential risk of impact in the days and weeks following discovery, when the orbit is poorly characterized. As the orbit is refined, the possibility of impact usually falls outside the prediction range, and the warning is downgraded or removed. However, if this potential hazard persists beyond more than a few months of observing coverage then the impact probability will generally rise to unusual levels and warrant more focused attention from the NEO community.

The warning rate is roughly proportional to the rate of discovery of potentially hazardous asteroids, and so, as the next generation of surveys starts to scan the skies, the rate of impact warning events will increase, creating a possible public relations challenge. This talk will review the reasons why potential impact warnings are an integral part of the survey program, and estimate the rate at which warnings can be expected in the coming years.