A Space-Based Optical Fence for Sunlit Debris: Aperture and Photon Budgets for a Low-Orbit Telescope Pair

This paper presents a computed design study of a civilian orbital-safety system based on passive optical detection of sunlight reflected from debris, from orbit. It is a computed study of a civilian orbital-safety system, with no targeting application and no weapon application. Status: SIMULATED, NOT MEASURED. Under the stated assumptions the sizing gives a reflected power at aperture W of 1.41e-13, a detected photons per exposure of 1.56e+04, and a snr of 123. Further computed quantities include limiting diameter cm approx of 1; aperture m of 0.4; slant range km of 500; exposure s of 0.05; survey area deg2 per hour of 3,600. The design is sized end to end from the stated assumptions in the deposited computation, so every headline number can be reproduced, challenged and revised. Where the approach performs poorly, that result is reported at the same size as the favourable results: the limitations section names the conditions under which this design should not be chosen. The contribution is a complete, auditable sizing for one operating principle, intended to be compared like-for-like with sizings built on other principles for the same task.