while the steady state sky plane distribution of the impactors is concentrated towards small solar elongation as shown by Chesley and Spahr (2004) their sky-plane distribution exhibits interesting behavior in the couple years leading up to impact. This behavior could be exploited to identify these objects well in advance of impact;
the requirement that a PHO have a MOID < 0.05 AU identifies 98% of all impactors even 100 years in advance of impact. The remaining 2% have much larger MOID and the error on the MOID will not identify these objects as potential impactors since they become PHOs only after encounter with another Solar System object, usually Jupiter. However, numerical exploration of their orbit evolution as routinely performed by impact monitoring sites will generally reveal these hazardous objects long before impact;
the MOIDs determined for objects with detections obtained during just a single lunation are very good;
the impactor model that we have developed is probably a good proxy for the unbiased orbit distribution of the large bolide population based on (1) the good agreement between the impactor orbit distribution and the orbit elements for impacting asteroid 2008 TC3 and (2) its sky-plane location at the time of discovery;
the next generation of all-sky surveys will identify a large fraction (J90%) of impactors >140 m diameter in a decade-long survey designed to find them;
the impact awareness time before impact can be many decades for impactors of any size as long as they are discovered before impact. The most likely impact awareness time for smaller impactors is zero;
the next generation surveys will probably image a small impactor before impact but it will likely be observed over too short a time span (e.g. one night) to allow either an accurate pre-impact orbit to be computed or its identification as an imminent impactor;