THE LATE-TIME X-RAY BEHAVIOR OF SHORT GAMMARAY BURSTS: IMPLICATIONS FOR ENERGETICS AND RATES THE DISTRIBUTION OF JET ANGLES FOR SHORT GAMMA-RAY BURSTS (GRBS) IS CRITICAL TO CONSTRAIN BECAUSE IT DIRECTLY AFFECTS THE TRUE ENERGY SCALE AND EVENT RATE PARA.METERS OF INTEREST FOR COINCIDENT SHORT GRB-GRAVITATIONAL WAVE DETECTIONS WITH ADVANCED LIGO. OUR CURRENT KNOWLEDGE OF THE OPENING ANGLE DISTRIBUTION COMES ALMOST EXCLUSIVELY FROM X-RAY OBSERVATIONS AT>1 DAY AFTER THE BURST. HERE WE PROPOSE XMM TDD OBSERVATIONS TO MONITOR A SHORT GRB AFTERGLOW AND CONSTRAIN ITS COLLIMATION EITHER FROM THE DETECTION OF A JET BREAK TO DETERMINE THE OPENING ANGLE OR THE NON-DETECTION OF A BREAK TO PLACE A LOWER LIMIT OF>10-15 DEGREES.