This proposal is responsive to NASA SBIR Subtopic S1.03: Passive Microwave Technology, specifically the fourth bullet item; "Low noise (<2000 K DSB), compactly designed (< 8 cm3), heterodyne mixers requiring low local oscillator drive power (<2 mW) with RF input frequency between 100 GHz to 1 THz." The proposed research is significant not only for the development of Schottky mixers that meet these requirements, but also for the creation of a receiver system, including the LO chain, that achieves the goals of high sensitivity, compact size, low total power requirement and operation across complete waveguide bands. The proposed receivers will meet all of the requirements for high resolution spectroscopic studies of planetary atmosphere's (including the Earth's) from spacecraft, as well as airborne and balloon platforms. The final contract deliverable will be a breadboard receiver module suitable for use on the proposed Vesper mission to probe the atmosphere of Venus. Perhaps more importantly, their exceptionally broadband performance, compactness and reliability will make them ideal for the broader range of scientific and commercial applications, which includes the extension of sophisticated test and measurement equipment to 1 THz and the development of low cost imaging systems for security applications and industrial process monitoring.