New Impact Report With Magnitude Requirements
http://128.102.38.40/impact/downloads/NEO_Chapter_1.pdf
The graph on page 47 clearly shows a magnitude limit of slightly higher than 20 meeting spaceguard goals and that a limiting magnitude >24 would be needed to detect 90% of 100m objects in 10 years. 24 gets about 80% in 10 years. A limiting magnitude of 22 is needed to make any significant headway over 10 years for 100m objects and is the limit needed to find 90% of objects > 300m over 10 years.
Regards,
Mark