Abstract: An apparatus for housing a focal plane array includes a tubular metal stem for housing a cryostat inside of it, and a hollow conical metal housing having its narrow end brazed onto the end of the tubular metal stem. A ceramic electrical interconnection assembly is rigidly sealed onto the wide end of the housing, having embedded electrical connections for providing electrical connections between the interior and exterior of the assembly. A metal ring-shaped mounting structure is rigidly attached to the ceramic interconnection assembly. A ceramic coldplate is sealed over the other end of the rigid metal tube in the interior of the structure for holding the focal plane array. The rigidity of the structure provides a known positional relationship between the coldplate and the mounting ring, to facilitate positioning the focal plane array during dewar installation. A metal cap is sealed to the mounting ring to provide a reworkable, hermetic closure.