Almost 70 % of the estimated 1000 NEA's larger than 1 km have been discovered. That is an absolute increase of almost 50% from the 219 discovered at the start of 1998 when NASA officially joined the program. With 4 years left to go NASA should be close to the goal of 90% (900 NEA's > 1 km) within 10 years despite the gradual decrease in discovery rate expected.

NASA is making steady progress on asteroids down to magnitude 21 (roughly 270 km) as indicated here. There have been nearly as many discoveries at the 20.5 (roughly 340 km) magnitude level as at magnitude 18 and no steep drop off until magnitude 21.5. Off course a 90% completion of the survey for the smaller objects will take much longer due to their greater numbers since their number is roughly inversely proportional to the square of their diameter. The story is even better for those NEA's already coming close to Earth known as Potentially Hazardous Asteroids (PHA's) which are by definition 22 magnitude (roughly 170 km) or larger. The relative proportion of magnitude 22 PHA's discovered is close to that for 21 magnitude objects in the larger population of NEA's since they are on average closer to Earth than the majority of the NEA population.

The various NEA search programs seem to be oscillating in their performance but LONEOS and Spacewatch are now discovering at peak levels despite the smaller population available for discovery. This is really impressive for LONEOS considering their scope is the smallest at only 0.6 m. LINEAR is still the champ, but the other programs are now making a greater portion of the discoveries. The Catalina program is also operational again.

Followup has gotten better as well. The percentage of objects discovered in 2003 which did not have orbits determined well enough to eliminate the <a href="http://neo.jpl.nasa.gov/risk/index_d.html>; risk of impact dropped to 1.4 % (6 of 439) in 2003 compared to 2.1 % (10 of 485) in 2002, 2.1 % (9 of 438) in 2001, and 1.4% (5 of 362) in 2000. The improvement is even clearer when the size of the objects on the list is noted. All but 1 of the 6 remaining impact risks discovered in 2003 were under 50 m and that one was discovered at the end of the year and is still being tracked. 3 remaining risks from 2002 are greater than 50 m, and only one is > 100 m. 6 remaining risks from 2001 are greater than or equal to 50 m, and 5 are 100 m or larger. An increasing proportion of objects discovered that can reach the surface are now being eliminated as potential impactors before they pass out of view. That data also suggests that the discovery rate of the smallest objects may be increasing although it is hardly solid evidence for that. If it is, it is probbaly due to the addition of a 1.8 m scope to the Spacewatch project which is 0.6 meters larger than any other currently in the program.

It's a target rich environment.

Regards,
Mark