Title: SigNals Of Opportunity: P-band Investigation (SNOOPI)  
Presenting Author: James Garrison
Organization: Purdue University
Co-Author(s): Jeffrey R. Piepmeier Rashmi Shah Cynthia Firman David Spencer Roger J. Banting Manuel A. Vega and Kameron Larsen 

SigNals Of Opportunity: P-band Investigation (SNOOPI) will be the first on-orbit demonstration of remote sensing using P-band (240-380 MHz) Signals of Opportunity (SoOp). SNOOPI will demonstrate a novel instrument which shows promise for measuring root-zone soil moisture (RZSM) and snow water equivalent (SWE) from space. Both RZSM and SWE are identified in the 2017-2027 Decadal Survey (ESAS 2017). P-band observations are required to penetrate into the root zone. SoOp measurements of phase-delay are proportional to SWE and the longer wavelength at P-band increases intervals between phase wrapping. The primary objective of SNOOPI is in-space validation of the P-band SoOp technique through an instrument prototype. This is a necessary risk-reduction step on the path to a science mission and will verify important assumptions about reflected signal coherence, robustness to the RFI environment, and our ability to capture and process the transmitted signal from orbit. The SNOOPI instrument consists of three subsystems: 1) The low noise front end (LNFE), developed from an airborne demonstration instrument and later redesigned in a CubeSat form factor; 2) The digital back end (DBE), a modification of the Cion instrument flying on CICERO that capitalizes on the extensive heritage of the Blackjack and TriG GPS receivers; and 3) an array of COTS antennas. Success with SNOOPI will retire critical risks associated with a P-band SoOp satellite instrument, and exit at TRL-7. In addition to enabling direct measurements of RZSM and SWE, which are not presently possible, this instrument will be orders of magnitude lower in size weight, power and cost (SWaP-C) than comparable monostatic radars due to the re-utilization of powerful anthropogenic signals.