[en] The back-projection angular-flux estimator employs a limiting process before the simulation, obviating the need to find average-flux values over finite spatial and angular intervals. The analysis was used to develop certain surface angular-flux estimators for the searchlight problem, with normal incidence and under some restrictions on azimuthal symmetry. The ability to estimate angular flux at a point is useful in radiation-transport calculations. It is hoped that the restriction to azimuthally symmetric situations can be relaxed in future work. It is noted that use of the back-project estimator makes possible certain analytic results without the need to perform any simulations