ScubaLee@aol.com (Ron Lee): >[0.49s vs. 1.01s] Why the apparent difference? aspect change during the pass? the real period is probably the 1.01s (or some other multiple of 0.49s). during the 0.49s portion, you were counting flashes off some surface that you could no longer see when you timed the 1.01s period -- the sun->object->you geometry wasn't Just Right any longer. this brings up a small question: asteroid observers can determine, to some extent, the spin axis of the body by digesting light curve data acquired under different viewing geometries. has this been attempted for objects in earth orbit? would it even be useful to do?