THz Radiometers: Architectures and Challenges for Space Missions

Using examples of integrated radiometers built for recent CubeSat missions, will discuss the tradeoff space between heterodyne (with and without a RF low-noise amplifier) vs direct-detection radiometer topologies for mm-wave and sub-mm-wave radiometers. We have delivered recently or are presently developing integrated radiometers at 183GHz for both the MIRATA and TROPICS CubeSat missions, a heterodyne 874GHz radiometer for IceCube CubeSat, and 670GHz and 325GHz integrated radiometers (both with and without a RF LNA) for future NASA missions. Based on these experiences, plus further design studies associated with these projects, we have developed some conclusions regarding the advantages and disadvantages of the various approaches. For the workshop presentation, I would (i) present a general overview of how a radiometer works; (ii) an overview of the different topologies used in the radiometer front-ends we have recently built, focusing on the particular challenges at >100GHz; (iii) compare the different topologies in terms of raw sensitivity, DSB vs SSB, power requirements, NEdT vs integration time.