SIGNALS OF OPPORTUNITY: P-BAND INVESTIGATION (SNOOPI) WILL BE THE FIRST ON-ORBIT DEMONSTRATION OF P-BAND (240-380 MHZ) SIGNALS OF OPPORTUNITY (SOOP). SNOOPI WILL DEMONSTRATE AN INNOVATIVE INSTRUMENT THAT SHOWS PROMISE FOR MEASURING ROOT-ZONE SOIL MOISTURE (RZSM) AND SNOW WATER EQUIVALENT (SWE) FROM SPACE. ACCURATE MEASUREMENT OF RZSM IDENTIFIED AS A PRIORITY TARGET VARIABLE FOR TECHNOLOGY DEVELOPMENT INITIATIVES IN ESAS 2017 IS OF NATIONAL IMPORTANCE AND CRITICAL TO FOOD PRODUCTION. MICROWAVE OBSERVATIONS AT P-BAND ARE NEEDED TO PENETRATE INTO THE ROOT ZONE. SNOW PROVIDES FRESHWATER DURING SPRING AND SUMMER FOR A LARGE PORTION OF THE WORLD AND PLAYS A CRITICAL ROLE IN HYDROLOGY AND WATER MANAGEMENT. SOOP MEASUREMENTS OF PHASE-DELAY ARE PROPORTIONAL TO SWE WHOSE MEASUREMENT WAS RECOMMENDED AS A PROGRAM ELEMENT IN ESAS 2017. CONVENTIONAL P-BAND RADAR AND RADIOMETERS ARE PRONE TO RF SPECTRUM ACCESS PROBLEMS AND REQUIRE VERY LARGE ANTENNAS TO OBTAIN SUFFICIENT SIGNAL-TO-NOISE RATIO OR SPATIAL RESOLUTION. SOOP REUSES SIGNALS FROM EXISTING TELECOMMUNICATIONS SATELLITES AND THUS DOES NOT REQUIRE A TRANSMITTER AS COMPARED TO A RADAR. SUCH SIGNAL EFFICIENCY MAKES SOOP VERY COST EFFECTIVE. THE OBJECTIVE OF SNOOPI IS IN-SPACE VALIDATION OF THE P-BAND SOOP TECHNIQUE AND A PROTOTYPE INSTRUMENT. THIS IS A NECESSARY RISKREDUCTION 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 IN SPACE. OUR BASELINE MISSION DESIGN IS DRIVEN BY THIS OBJECTIVE WHICH WILL BE MET THROUGH DEMONSTRATING MEASUREMENT OF THE COMPLEX REFLECTION COEFFICIENT OVER VARIOUS LAND SURFACE CONDITIONS AND SHOWING THAT STATISTICS OF THE REFLECTION COEFFICIENT MAGNITUDE AND PHASE RETRIEVAL MEET THE WORKING REQUIREMENTS FOR A FUTURE RZSM AND SWE MISSION. WE ARE ENTERING THE INVEST PROGRAM WITH A TRL5 TECHNIQUE AND INSTRUMENT AND BUILDING UPON OUR TEAM S SUCCESS ON SEVERAL COMPETITIVELY SELECTED AND INTERNALLY FUNDED PROJECTS. OUR INSTRUMENT CONSISTS OF THREE SUBSYSTEMS: 1) THE LOW NOISE FRONT END (LNFE) DEVELOPED FROM THE SOOP-AD (IIP-13) AIRBORNE DEMONSTRATION INSTRUMENT AND REDESIGNED FOR A CUBESAT FORM FACTOR UNDER GSFC INTERNAL FUNDING; 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. LNFE HAS A PATENT-PENDING ARCHITECTURE THAT USES AN INTERNAL CALIBRATION NETWORK BASED UPON OUR EXPERIENCE WITH THE AQUARIUS AND SMAP MISSIONS. IT ALSO IS CAPABLE OF ANTENNA SWAPPING TO SUPPRESS THE EFFECTS OF ANTENNA PHASE AND GAIN IMBALANCES. RF CIRCUITS ARE SHIELDED FROM OUT OF BAND SIGNALS AND SPACECRAFT-GENERATED ELECTROMAGNETIC INTERFERENCE (EMI). DBE EMPLOYS A COMBINATION OF OFF-THE-SHELF HARDWARE WITH A CUSTOM-DESIGNED RF/CLK/HOST BOARD AND WILL BE MODIFIED TO ACCOMMODATE THE RAD-TOLERANT SPACE MICRO CUBESAT SPACE PROCESSOR (CSP) TO MAKE THE INSTRUMENT SUITABLE FOR A FUTURE NASA CLASS D MISSION. FOUR P-BAND DOWN-CONVERTERS AND A HIGH-PERFORMANCE SAMPLING CLOCK ARE USED TO ACQUIRE DATA IN TWO POLARIZATIONS FROM THE TWO ANTENNAS (ZENITH AND NADIR). SUCCESS WITH SNOOPI WILL RETIRE THE CRITICAL RISKS ASSOCIATED WITH A P-BAND SOOP SATELLITE MISSION AND WE WILL EXIT WITH A TRL-7 INSTRUMENT. THIS INSTRUMENT WILL ENABLE DIRECT MEASUREMENTS OF RZSM AND SWE THAT ARE NOT PRESENTLY POSSIBLE AND WILL ALSO BE ORDERS OF MAGNITUDE LOWER IN SIZE WEIGHT AND POWER (SWAP) THAN COMPARABLE ACTIVE RADARS DUE TO THE RE-UTILIZATION OF POWERFUL ANTHROPOGENIC SIGNALS. COUPLED WITH THE USE OF SMALL WIDE BEAM ANTENNAS A P-BAND SOOP MISSION IS AN IDEAL CANDIDATE FOR A LARGE CONSTELLATION OF MICRO-SATELLITES OR HOSTED PAYLOADS. THIS CONSTELLATION COULD BE PROPOSED TO A FUTURE EARTH VENTURE/CONTINUITY OR EARTH SYSTEM EXPLORER PROGRAM.