Abstract: Guidance apparatus for a tactical guided missile uses a dual-mode sensor having both active millimeter wavelength RF sensing capability and passive infrared sensing capability within a single aperture. A dual reflector-antenna assembly is formed by chemical vapor deposition of dielectric material transparent to infrared and RF radiation. Embedded within the reflector assembly is an RF microstrip antenna array, formed by thin-film metalization techniques, which defines an antenna beam axis. A surface of the reflector assembly is ground, optically polished, and coated with infrared reflective material to form a primary reflecting surface of a Cassegrainian optical system, which also includes a secondary mirror, for defining an infrared detection beam axis coincident with the antenna beam axis. Infrared radiation from a target is concentrated by the Cassegrainian optical system onto an infrared detector to produce a first guidance signal.