An RF-transparent sunshield membrane covers an antenna reflector such as a parabolic dish. The membrane includes at least two dielectric sheets of polyimide film 1 mil thick. The surface of the outer film facing away from the reflector is coated with an electrically semiconductive coating such as vapor-deposited germanium having a thickness in the range of 200 .ANG. to 600 .ANG.. A member, such as a glass fiber mat, may be located in the space between the two dielectric sheets for maintaining the sheets in spaced-apart relationship. In another embodiment of the invention, the surface of the film facing the reflector may be reinforced by an adhesively attached polyester or glass fiber mesh.

An article is coated with a mixture of a high absorptance pigment, a low absorptance pigment, a low emittance material, and a high emittance binder. Each of the components of the coating are stable when exposed to a space environment. The amounts of the high absorptance pigment and the low absorptance pigment are selected to produce an absorptance of the coating of from about 0.20 to about 0.90, and the amount of the low emittance material is selected to produce an emittance of the coating of from about 0.25 to about 0.90. The low absorptance pigment is preferably a white pigment such as zinc oxide. The high absorptance pigment is preferably a black pigment such as cupric oxide, cobalt oxide, or manganese dioxide. The low emittance material is preferably a metal such as aluminum. The binder is preferably a ceramic such as potassium silicate.

An RF-transparent sunshield membrane covers an antenna reflector such as a parabolic dish. The membrane includes a single dielectric sheet of polyimide film 1 mil thick. The surface of the film facing away from the reflector is coated with a layer of semiconductor material such as vapor-deposited germanium having a thickness in the range of 200 .ANG. to 600 .ANG.. In another embodiment of the invention, the surface of the film facing the reflector may be reinforced by an adhesively attached polyester or glass fiber mesh.

A high-efficiency active printed-circuit antenna system for pulsed frequency-hopping space radar electronically scanned in two planes encompasses in its timing diagram the transmission of a horizontal polarization pulse, the reception of echoes from a previous horizontal polarization pulse, the transmission of a vertical polarization pulse and the reception of echoes from a previous vertical polarization pulse. The system comprises several thousand MMIC modules distributed over the antenna and each connected to a printed-circuit radiating element comprising a plurality of dual polarized square patches connected by microstrip lines which excite them with the same amplitude and the same phase at two perpendicular ports. Switching between the two ports procures transmission or reception with horizontal or vertical polarization.

An RF-transparent sunshield membrane covers an antenna reflector such as a parabolic dish. The blanket includes a single dielectric sheet of polyimide film 1/2-mil thick. The surface of the film facing away from the reflector is coated with a transparent electrically conductive coating such as vapor-deposited indium-tin oxide. The surface of the film facing the reflector is reinforced by an adhesively attached polyester or glass mesh, which in turn is coated with a white paint. In a particular embodiment of the invention, polyurethane paint is used. In another embodiment of the invention, a layer of paint primer is applied to the mesh under a silicone paint, and the silicone paint is cured after application for several days at room temperature to enhance adhesion to the primer.