Monte Carlo simulations are used to investigate and evaluate different design options for the SILEX acquisition beacon. A minimum specification for the quality of the optical coupling between the laser diodes and the beacon output for which the beacon meets its power specification with the required reliability is established. An improved reliability is demonstrated for beacon designs with an optimized thermal design including the control of the thermal wall temperature and the conductive coupling between the beacon emission unit and the terminal radiator. Such an optimized thermal design also offers the possibility of mass savings of the optical terminal, since only a very light thermal wall is needed for the beacon. The total power control of the laser diodes is demonstrated to be the best mode of operation.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.