Photonics-based Microwave Radiometer for Hyperspectral Earth Remote Sensing

Space-based microwave radiometers (MRs) have a long history of providing critical inputs for retrieval algorithms that generate accurate estimates of geophysical properties of the Earth's surface and atmosphere. Mission cost reduction pressure has led to increased use of small spacecraft (e.g. CubeSats and SmallSats) for scientific and operational Earth observation applications. The need for miniaturized MR electronics that fit into SmallSats and maintain performance poses a challenge for conventional MR technologies. Channel filters are one driver of MR size and weight. Microwave photonics (MWP) fabricated on silicon photonic integrated circuits (PICs) is one means to dramatically reduce the size of these filters enabling SmallSat platform integration and enhanced measurement capability. In this paper, we address the performance requirements for PICs to provide a viable path for low cost, size, weight and power (c-SWaP) MRs. We present experimental results of a silicon PIC filter development and a new electro-optic modulator (EOM) design that will integrate monolithically with these filters. The performance of an integrated MWP-based MR is modeled and compared to an operational MR. It is shown that the MWP design using the new EOM can provide radiometric performance comparable to conventional MRs but within a dramatically smaller sensor volume and in a purely silicon platform enabling low cost.