If elsets from OIG are going to be at a premium, has anyone thought of writing a utility which would go thru a file of elsets and divide it, or at least the catalog numbers, into 2 sets: a) those whose orbits will be illuminated in the dark above a given site during a given period, i.e., those which are potentially observable if the drag produces a suitable mean anomaly --and-- b) those which definitely won't be visible. With a utility like this, people wouldn't have to waste requests for elsets of objects they won't see anyway. 'Course, this wouldn't be absolutely perfect. E.g., you'd still have to include such as shuttles and decayers which might be self-luminous. Cheers. Walter Nissen firstname.lastname@example.org -81.8637, 41.3735, 256m elevation --- Carpe noctem!