Speaker: Prof. James L. Garrison, Purdue University

This presentation will review progress made to advance the SoOp technique. Three different examples will be presented in approximate order of technical maturity.  First, Global Navigation Satellite System Reflectometry (GNSS-R) is the most advanced SoOp technique. CYGNSS, launched in 2016, provides observations of ocean winds and various land surface observations (e.g. soil moisture and flood inundation) in the tropics.  A large and growing science community has evolved around using CYGNSS data.  Second, P-band (<400 MHz) communication signals exist in frequencies low enough to penetrate through dense vegetation and soil. 

No science allocation exists in this band.  SoOp techniques, therefore, offer a new capability for sensing Root-Zone Soil Moisture (RZSM), an essential climate variable that, at present, can only be obtained through the assimilation of surface soil moisture observations. SNOOPI (SigNals Of Opportunity: P-band Investigation) is a CubeSat mission launched in April 2024 to demonstrate spaceborne P-band SoOp remote sensing. Finally, wide-band (~1GHz) communications broadcast signals in Ku-band (12-18 GHz) and higher can theoretically provide altimetry (sea surface height) at cm-level precision. 

A constellation of passive SoOp receivers could be launched for a fraction of the cost of a single active radar altimeter, substantially increasing the coverage, particularly in coastal regions.  Prof. Garrison will conclude the talk with speculative concepts and ideas for future research directions.