IN THIS PROPOSAL WE WILL EXPLORE THE FEASIBILITY OF MULTIPLE GEOSYNCHRONOUS GNSS REMOTE SENSING OBSERVATIONS USING ON-ORBIT DATA FROM THE GOES-16 AND GOES-17 GPS NAVIGATION RECEIVERS: SCINTILLATION DETECTION RO PROFILING AND SURFACE REFLECTIONS. ADDITIONALLY WE WILL PERFORM TRADE SPACE STUDIES ASSESSING THE ON-ORBIT RECEIVER REQUIREMENTS FOR MAKING USEFUL OBSERVATIONS OF THE EARTH'S ATMOSPHERE AND SURFACE USING GNSS SIGNALS FROM A GEOSYNCHRONOUS (GEO) SATELLITE PLATFORM FOR THE BENEFIT OF FUTURE GNSS REMOTE SENSING MISSIONS. WE BELIEVE THAT THE MOST PROMISING NEW SCIENCE ARE THE ATMOSPHERIC MEASUREMENTS POSSIBLE WITH THE GOES GPS RECEIVERS. RADIO OCCULTATION (RO) FROM GEOSYNCHRONOUS ORBIT HOLDS THE POTENTIAL TO PROVIDE UNIQUE TEMPORAL AND SPATIAL ATMOSPHERIC MEASUREMENTS NOT POSSIBLE FROM GROUND AND LOW EARTH ORBIT (LEO) SPACE BASED RECEIVERS INCLUDING NEW OBSERVATIONS OF THE UPPER ATMOSPHERE. THIS PROJECT WILL EXPLORE THE POTENTIAL OF GEO GNSS RECEIVERS TO GENERATE NEW OBSERVATIONS BOTH ABOVE EXISTING GNSS-RO LEO SATELLITES AS WELL AS ATTEMPT TO GENERATE UNIQUE GEO RO PROFILES THROUGH THE ATMOSPHERE. WE WILL ANALYZE ARCHIVED AND FUTURE GOES DATA SETS TO DEVELOP ATMOSPHERIC SCINTILLATION DETECTION ALGORITHMS USING SEVERAL TECHNIQUES TAILORED TO THE KNOWN LIMITATIONS OF THE GOES DATA SET. NOTABLY BOTH AMPLITUDE AND PHASE MEASUREMENTS FROM GPS SIGNALS TRACKED BY THE GOES RECEIVERS WILL BE USED FOR OBSERVING UPPER AND LOWER ATMOSPHERIC SCINTILLATIONS. INITIAL MODELING HAS BEEN PERFORMED THAT INDICATES THAT THE LARGE DISTANCE BETWEEN THE GPS TRANSMITTERS AND THE GOES RECEIVERS MAY PRESENT AN ADVANTAGE OVER LEO SATELLITES. ADDITIONALLY WE WILL DEVELOP TECHNIQUES TO GENERATE RO BENDING ANGLE PROFILES FROM GOES OBSERVATIONS AND EXPLORE METHODS TO INVERT THESE PROFILES TO REFRACTIVITY AND SUBSEQUENT ESTIMATIONS OF TEMPERATURE PRESSURE AND (POTENTIALLY) WATER VAPOR IN THE TRAVERSED ATMOSPHERIC COLUMN. EVIDENCE INDICATES THAT THE GOES RECEIVERS REGULARLY TRACK SIGNALS THROUGH THE IONOSPHERE AND INTO THE TROPOSPHERE THUS ENABLING THE RETRIEVAL OF THESE LONG DURATION OCCULTATION EVENTS WITH CUSTOM PROCESSING ALGORITHMS TO GENERATE NEW ATMOSPHERIC OBSERVATIONS. ADDITIONALLY IT HAS BEEN DEMONSTRATED THAT COHERENT GRAZING ANGLE SURFACE REFLECTIONS ARE DETECTABLE BY LEO RO GPS RECEIVERS. THE PRESENCE OF SURFACE REFLECTIONS IN THE GOES DATA WILL BE EXPLORED AS PART OF THIS PROJECT PARTICULARLY OVER THE GREENLAND ICE SHEET WHERE A CONVERGENCE OF GOES MEASUREMENTS AND HISTORIC EVIDENCE OF REFLECTIONS IN LEO RO DATA MAKE THE POSSIBILITY OF DETECTION MOST LIKELY. FINALLY WE WILL PERFORM A TRADE SPACE STUDY INTO THE ENHANCED AND/OR OPTIMAL GNSS REMOTE SENSING INSTRUMENT CONFIGURATIONS FOR A) FUTURE STANDARD GEOSYNCHRONOUS GNSS INSTRUMENTS (OR MISSIONS ABOVE THE GNSS CONSTELLATIONS SUCH AS MMS) AND B) CUSTOM GNSS REMOTE SENSING MISSION DESIGNS WITH DEDICATED GNSS REMOTE SENSING INSTRUMENTS. DATA FROM THE COSMIC-2 RO AND THE CYGNSS GNSS-REFLECTION MISSIONS WILL BE USED TO "ANCHOR" THIS ANALYSIS TO REALITY AND PROVIDE INCREASED CONFIDENCE IN THEIR PREDICTIONS OF THE GNSS PERFORMANCE ACHIEVABLE AT HIGHER ALTITUDES FOR VARIOUS INSTRUMENT CONFIGURATIONS. IN SUMMARY THIS PROPOSED WORK WILL ENABLE NEW ATMOSPHERIC MEASUREMENTS USING THE EXISTING GOES NAVIGATION RECEIVER DATA SETS AND MAKE A SIGNIFICANT STEP FORWARD IN THE UNDERSTANDING OF THE FEASIBILITY OF PERFORMING GNSS REMOTE SENSING IN GEOSCYNCHRONOUS ORBITS FOR FUTURE MISSIONS.