They pointed out that for debris of diameter less than one cm, collision avoidance is unnecessary because shielding will be provided that allows the SS to take a hit. Debris of diameter greater than 10 cm can be tracked by current ground-based radar. A catalogue exists already for 7000 such objects, giving size and orbital data. Collision can then be avoided by a maneuver of the spacecraft. Debris in the diameter range of one cm to 10 cm are too large for shielding and too small for current ground- based tracking.
Collision avoidance requires the ability to predict accurately the debris trajectory.
The required lead time for this purpose, in advance of an avoidance maneuver, is at least an hour and a half, or one orbit at SS altitude, about 400 km. The primary cause of uncertainty in the prediction of debris trajectory is atmospheric drag. This led to the conclusion that at least some of the debris objects in this size range are made of materials that may possess dielectric characteristics, and not made of aluminum or other metal that is regularly assumed. See Figure 2 for a drawing of the SBV telescope. Seven organizations have banded together in a consortium to offer seven different types of monitors of space particulates, covering sizes form 0.1 micrometer to 10 cm.