A cold shield having an evacuated enclosure having a first aperture therein for transmission of radiations and a baffle disposed within the enclosure having a second aperture larger than the first aperture and aligned with the first aperture and having a detector disposed on a surface thereof opposite the second window. The first aperture includes a radiation transmissive member and a radiation opaque member disposed on the surface of the radiation transmissive member and external to the evacuated enclosure. A radiation band pass filter is disposed on the radiation transmissive member. The interior of the baffle is coated with an absorptive low reflecting material and the exterior surface of the baffle opposing the first aperture is coated with an absorptive low reflecting material.