Aerospace applications require artificial stars in the laboratory testing of star sensors or trackers. The precise angular testing of these instruments requires that the star simulators or simulacrums provide nearly plane wavefronts and infinitesimal diametral angular subtense of the source. The paper presents performance requirements for the simulator to be used on an advanced space systems program. The paper discusses the parametric and tradeoff studies leading to the pinhole size, radiometric requirements, and collimation tolerance and traces the design of the illumination system. The major lens design aim is to provide a diffraction-limited, long-focal-length objective. Spherical and chromatic aberration and related secondary aberrations such as zonal spherical, secondary color, and spherochromatism need to be corrected to a degree that permits diffraction-limited performance. The paper also outlines procedures followed in the lens design and reviews aspects of mechanical, electrical, and thermal design.