NUMEROUS STUDIES HAVE REVEALED RAPID CHANGES IN ICE DISCHARGE FROM GREENLAND WITH MANY OF THE ICE SHEET S OUTLET GLACIERS HAVING ACCELERATED DRAMATICALLY OVER THE LAST TWO DECADES. THESE OBSERVATIONS ARE SIGNIFICANT IN THAT THEY SHOW GREENLAND S MASS BALANCE CAN FLUCTUATE RAPIDLY AND UNPREDICTABLY. DESPITE THE LARGE MAGNITUDES OF THESE CHANGES WE DO NOT YET UNDERSTAND THE UNDERLYING PROCESSES CONTROLLING FAST FLOW WELL ENOUGH TO DETERMINE THEIR LONG-TERM IMPACT ON SEA LEVEL. OBSERVATIONS MADE OVER THE LAST SEVERAL YEARS INCLUDING THOSE FROM OUR PRIOR PROJECTS INDICATE LESS POTENTIAL FOR RUN-AWAY ICE LOSS THAN WAS INITIALLY FEARED WHEN THE FIRST OBSERVATIONS OF RAPID CHANGE WERE MADE. NONETHELESS OUTLET GLACIER DYNAMICS REMAIN A WILD CARD IN THE SEA-LEVEL PROJECTIONS AS NOTED IN THE LAST TWO INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC) ASSESSMENTS. IMPROVING SUCH PREDICTIONS AND GAINING A FIRM UNDERSTANDING OF THE DYNAMICS THAT DRIVE MASS BALANCE REQUIRES ANNUAL TO SUB-ANNUAL OBSERVATIONS OF OUTLET GLACIER VARIABILITY (VELOCITY ELEVATION AND ICE FRONT POSITION) TO AVOID ALIASING OF THE RAPIDLY VARYING SIGNALS. FURTHERMORE ALTHOUGH GLACIERS CAN CHANGE FAR MORE RAPIDLY (SUB-ANNUAL SCALES) THAN EXPECTED DECADAL-SCALE OBSERVATIONS ARE STILL REQUIRED TO PROVIDE THE KNOWLEDGE NEEDED FOR CENTURY-SCALE PROJECTION. THE TECHNOLOGY FOR MEASURING VELOCITY IN GREENLAND IS MATURE AS DEMONSTRATED THROUGH OUR ONGOING AND PAST GREENLAND ICE MAPPING PROJECTS (GIMP-1&2). THROUGH THESE PROJECTS WE HAVE REPEATEDLY MEASURED ICE VELOCITY IN GREENLAND ESTABLISHING A RECORD FROM 2000 TO PRESENT. THROUGH GIMP-3 WE WILL CONTINUE THIS EFFORT TO EXTEND THE RECORD OF ICE FLOW VELOCITY THROUGH 2022 A PERIOD WHEN GREENLAND LIKELY WILL CONTINUE TO EVOLVE RAPIDLY WITH THE CURRENT WARMING. THE GIMP-3 PRODUCTS WILL BE ENTIRELY COMPATIBLE WITH PRIOR PRODUCTS BUT WE WILL TAKE ADVANTAGE OF NEW SENSORS THAT HAVE BEEN LAUNCHED IN THE LAST 5 YEARS (LANDSAT 8 SENTINEL 1A/B AND SENTINEL 2A/B) TO GREATLY IMPROVE TEMPORAL AND SPATIAL SAMPLING. IN ADDITION WE WILL TAKE ADVANTAGE OF THE IMPROVED AVAILABILITY OF LANDSAT TM DATA TO EXTEND THE RECORD BACK IN TIME TO 1984. IN CONJUNCTION WITH THE RESULTS FROM OUR EARLIER PROJECTS GIMP-3 WILL PROVIDE AN IMPORTANT NEARLY FOUR-DECADE-LONG PRECURSOR DATA SET FOR THE NISAR L-BAND SAR MISSION SCHEDULED TO LAUNCH NEAR THE END OF THE DECADE AS A JOINT EFFORT BETWEEN NASA AND THE INDIAN SPACE AGENCY. IN ADDITION GIMP-3 VELOCITY MEASUREMENTS WILL PROVIDE A STRONG COMPLEMENT TO THE THINNING MEASUREMENTS MADE BY NASA S ICESAT-2 AND ICEBRIDGE MISSIONS.