A GLOBAL SUB-SURFACE OCEAN AT EUROPA IS LIKELY AND PROVIDES THE FIRST OF THREE KEY REQUIREMENTS FOR LIFE LIQUID WATER. THE POSSIBILITY OF LIFE FORMING IN THIS SUB-SURFACE OCEAN RELIES IN PART ON TRANSFER OF OXIDANTS FROM THE IRRADIATED ICE SURFACE TO THE SHELTERED OCEAN BELOW. THIS TRANSFER DEPENDS ON THE THICKNESS OF THE ICE SHELL: A THICK STAGNANT CRUST WOULD LIKELY HALT THE DEVELOPMENT OF INDIGENOUS LIFE. THE DETERMINATION OF EUROPA S CRUSTAL THICKNESS IS AN IMPORTANT EXOBIOLOGICAL ISSUE AND ONE OF THE CONTROVERSIAL TOPICS OF PLANETARY SCIENCE. THE LANDER-INTERNAL SEISMOMETER TO INVESTIGATE ICE AND OCEAN STRUCTURE (SIIOS) PROVIDES DIRECT GEOPHYSICAL MEASUREMENTS TO PROBE THE ICE SHELL AND THE ICE-WATER INTERFACE EXPLOITING WELL-ESTABLISHED TERRESTRIALLY-DEMONSTRATED METHODS. NATURALLY-GENERATED LOW FREQUENCY SEISMIC WAVES RESULTING FROM FRACTURE PROPAGATION FAULT MOVEMENTS AND TIDAL EFFECTS PROPAGATE OVER GREAT DISTANCES IN ICE ENABLING DETECTION OF THE ICE-WATER BOUNDARY AND THE SOUNDING OF ANY POCKETS OF LIQUID WITHIN THE ICE LAYER AT DISTANCES ON THE SCALE OF EUROPA. ANALYSIS OF THE SIGNALS FROM THE 3-AXIS SIIOS SEISMOMETER PERMITS THE MEASUREMENT OF ICE THICKNESS AND STRUCTURE. OUR TEAM HAS ALREADY CONDUCTED MEASUREMENTS OF TERRESTRIAL SEISMIC EVENTS IN ICE INCLUDING TWO NASA-FUNDED PSTAR TERRESTRIAL ANALOG FIELD PROGRAMS WITH THE SIIOS SEISMOMETER. WE DEPLOYED OUR CANDIDATE SEISMOMETER ON A PURPOSE-BUILT LANDER SIMULATOR ON A SUBGLACIAL LAKE IN NORTHWEST GREENLAND AND A GLACIER IN GULKANA ALASKA. BOTH DEPLOYMENTS HAVE DEMONSTRATED THE ABILITY OF OUR INSTRUMENT TO DETECT SEISMIC PHASES UNIQUE TO ICE-WATER INTERFACES IN A EUROPAN ANALOG ENVIRONMENT AND ALSO CONSTRAIN THE THICKNESS OF AN ICE COLUMN. WE HAVE CONDUCTED FINITE ELEMENT ANALYSIS STUDIES OF OUR LANDER SIMULATOR DEMONSTRATING OUR ABILITY TO PREDICT SEISMIC SIGNAL TRANSMISSION FOR A VAULT-MOUNTED SENSOR. RELEVANCE. SIIOS IS DIRECTLY RELEVANT TO ICEE 2 GOALS TO DETERMINE THE PROXIMITY TO LIQUID WATER AND RECENTLY ERUPTED MATERIALS AT THE LANDER S LOCATION (SDT GOAL 2B) AND CHARACTERIZE DYNAMIC PROCESSES ON EUROPA S SURFACE AND ICE SHELL OVER THE MISSION DURATION (SDT GOAL 3B). SIIOS DETERMINES WHETHER OR NOT THE EUROPAN ICE SHELL OVERLAYS A LIQUID OCEAN QUANTIFIES THE ICE SHELL THICKNESS AND IDENTIFIES WHETHER OR NOT NON-ICE INCLUSIONS EXIST. THE SIIOS 3-AXIS SEISMOMETER BASED ON THE SILICON AUDIO INC. COTS INSTRUMENT IS 300 GRAMS REQUIRING 120 MW OF POWER WITH A CURRENT NOISE FLOOR OF 10-8M/S2/SQRT(HZ) OVER THE BAND 0.005 TO 600 HZ. WE IMPROVE THE NOISE FLOOR TO 10-9M/S2/SQRT(HZ) OVER THE BAND 0.005 - 300HZ PRESERVING MASS AND POWER. THE INSTRUMENT IS INSENSITIVE TO TILT ANGLE AND FITS WITHIN THE VOLUME IDENTIFIED IN THE PIP AS BOX D (75 X 75 X 45MM). THE INSTRUMENT IS CURRENTLY TRL4 AND WILL BE TRL6 BY 2021. THE SIIOS CONTROL ELECTRONICS CAN BE ACCOMMODATED IN A COMMON INSTRUMENT ELECTRONICS CHASSIS AND IS BASED ON HERITAGE DESIGNS FROM OUR PARTNER SPACE DYNAMICS LAB. GOALS. THE GOALS OF THE SIIOS EXPERIMENT ARE: 1) DETERMINE LANDER REQUIREMENTS TO CONDUCT VAULT-BASED SEISMOMETRY; 2) ADVANCE THE SIIOS 3-AXIS SEISMOMETER WITH IMPROVED PERFORMANCE TO TRL6 BY 2021; 3) ESTABLISH COMPATIBILITY WITH LANDER RESOURCES AND DEVELOP THE INSTRUMENT SYSTEM ARCHITECTURE; 4) COMPLETE THE HERITAGE ASSESSMENT RISK IDENTIFICATION AND MITIGATION AND TIME-PHASED COST AND SCHEDULE ESTIMATES. METHODOLOGY. 1) QUANTIFY THE ABILITY OF ON-LANDER SEIMIC INSTRUMENTS TO SENSE SEISMICITY TO ESTABLISH INSTRUMENT REQUIREMENTS; 2) BUILD TEST AND QUALIFY A SIIOS SEISMOMETER WITH AN IMPROVED NOISE FLOOR; 3) WORK WITH THE LANDER TEAM TO ESTABLISH INTERFACES AND RESOURCE ALLOCATION CONSISTENT WITH A SIIOS SYSTEM-LEVEL DESIGN; 4) ASSESS SIIOS HERITAGE RISK IDENTIFICATION AND MITIGATION AND PREPARE PROGRAM TIME-PHASED FLIGHT COST AND SCHEDULE. THE UNIVERSITY OF ARIZONA IS PROVIDING 14% ($283K) OF THE PROJECT COST THROUGH CONTRIBUTED FUNDS.