Geometric relations have been developed to express the orientation between the sun, a single high-altitude satellite, and a number of satellites at a lower altitude. It was assumed that the satellites at lower altitude were sufficiently numerous and that their orbital characteristics were sufficiently random so that their locations at a given instant in time could be considered on a statistical basis. With these assumptions, the instantaneous probability that the upper satellite will "see" a randomly located lower satellite under specified lighting conditions is presented in a series of graphs. Five general cases are considered, each requiring line-of-sight visibility between the upper and lower satellites, but under progressively more restrictive lighting conditions. The general results are then applied to several illustrative examples by placing the observation satellite at synchronous altitude and considering the satellites (or other objects) that were actually in orbit at lower altitudes as of January 15, 1967. 61 pp. Ref.