Signals of Opportunity Synthetic Aperture Radar for High Resolution Remote Sensing of Land Surfaces

The goal of our proposal is to develop the Synthetic Aperture Radar (SAR) Technology based on a unique combination of P-band Signals of Opportunity (SoOp) technique and sparse array technology for high resolution satellite remote sensing of Snow Water Equivalent (SWE) and Root Zone Soil Moisture (RZSM). The SoOpSAR concept will potentially lead to a significant reduction of cost and risk by an order of magnitude in comparison with the current available SAR technologies, which require dedicated high power transmit source, large deployable antenna aperture, complex deployment and hence large satellites. Specifically, we target the second element of the IIP call on Instrument Concept Demonstration (ICD) to advance the TRL of SoOpSAR technology concept from 2 to 3. The objectives of the proposed research are: 1. Complete proof-of-concept demonstration of the SoOpSAR technology by ground-based experiments; 2. Advance system concept by performing trade studies for resolution, swath, sparse array optimization, and uncertainty analysis of receiver timing and positioning errors. The proposed SoOpSAR based on P-band Signals of Opportunity will provide an order of magnitude improvement in spatial resolution than the conventional SoOp technologies to enable applications, such as flood monitoring/forecasts and precision farming. Furthermore, the conventional spaceborne monostatic P-band SAR is currently not allowed to operate over North America and Western Europe due to frequency allocation by the International Telecommunication Union, which designates the US Space Objects Tracking Radar (SOTR) as the primary user of the 435 MHz band. The proposed SoOpSAR technology, operating at 260 and 360 MHz bands, could fill the gap for high-resolution radar imaging of land surfaces at P-band. High resolution (~100m) remote sensing of soil moisture/snow water content is critical for modeling of land surface hydrological processes and applications. Despite their importance, SWE and RZSM, which are critical water storage elements, are arguably two of the least measured hydrologic states in the Earth System, in part due to the challenges and high cost of current spaceborne SAR technologies, which require large antenna apertures and hence large satellites. The proposed SoOpSAR concept is highly relevant to NASA Earth Science, specifically motivated by the stated science goal in the 2014 NASA Science Plan to: "Enable better assessment and management of water quality and quantity to accurately predict how the global water cycle evolves in response to climate change." The ability of SoOpSAR will also address the needs of terrestrial snow water storage designated as one of the critical variables for the Earth Explorer Missions in the 2017 NASA Decadal Survey report. We have completed a preliminary system performance analysis. The expected signal to noise ratio is exceptional and will enable accurate soil moisture and snow water content retrieval. For the IIP-ICD SoOpSAR proof-of-concept testing, we will develop five receivers for testing using a ground-based moving vehicle. The receivers will be mounted with various horizontal spacings to acquire data to simulate and test the use of sparse array concept for high across-track resolution processing. We will also conduct detailed system error analyses to determine the requirements on sparse array position control and knowledge accuracy requirements. Our team members have demonstrated expertise in science algorithms, SoOp techniques, and SAR technologies and will complete the proposed tasks on cost and schedule.

Increase scientific understanding of natural phenomena using remote sensing

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