DEBRIS DISKS ARE VERY USEFUL TRACERS OF THE DYNAMICAL STRUCTURE OF PLANETARY SYSTEMS: DUST GRAINS PRODUCED BY COLLISIONS OF LEFTOVER PLANETESIMALS TRACE THE POPULATION OF THEIR PARENT BODIES WHOSE LOCATIONS AND ORBITAL DISTRIBUTION ARE SCULPTED BY GRAVITATIONAL PERTURBATIONS OF THE PLANETS IN THE SYSTEM (ANALOGOUS TO OUR OWN ASTEROID BELT AND KUIPER BELT SCULPTED BY THE MAJOR PLANETS IN THE SOLAR SYSTEM). IN THIS PROJECT WE WILL ELUCIDATE THE PLANETARY SYSTEM ARCHITECTURE OF THREE NEARBY DEBRIS DISK SYSTEMS VEGA FOMALHAUT AND EPSILON ERIDANI WHICH CONTAIN MULTI-COMPONENT STRUCTURES INCLUDING INNER AND OUTER BELTS (ASTEROID BELT AND KUIPER BELT ANALOGS) OBSERVED BY MULTIPLE INSTRUMENTS ABOARD SPITZER AND HUBBLE AND ARE OF INTERMEDIATE AGE (A FEW 100 MYR). THIS AGE CORRESPONDS TO THE SO-CALLED LATE HEAVY BOMBARDMENT EVENT IN OUR OWN SOLAR SYSTEM'S HISTORY WHEN THE PLANETESIMALS LEFTOVER FROM PLANET FORMATION WERE DYNAMICALLY PERTURBED AND THE GIANT PLANETS ARE INFERRED TO HAVE UNDERGONE A DRAMATIC ORBITAL REARRANGEMENT. WE PROPOSE TO USE DYNAMICAL MODELING AND STABILITY ANALYSIS TO PREDICT THE PROPERTIES OF PRESENTLY UNSEEN PLANETS IN THESE SYSTEMS THAT CAN ACCOUNT FOR THE OBSERVED DISK FEATURES AND GAPS BETWEEN THE INNER AND OUTER DISK COMPONENTS. OUR PREDICTIONS CAN BE TESTED IN FORTHCOMING DIRECT DETECTION OBSERVATIONAL CAMPAIGNS.THIS PROJECT RESPONDS DIRECTLY TO THE NESSF SOLICITATION FOR COMPUTATIONAL AND/OR THEORETICAL MODELING THAT EXPLOITS DATA COLLECTED BY SPACECRAFT-BORNE INSTRUMENTS. THIS RESEARCH ADDRESSES PRIORITY QUESTIONS IN PLANETARY SCIENCE AS OUTLINED IN THE NRC'S VISION AND VOYAGES IN PLANETARY SCIENCE IN THE DECADE 2013-2022 AND NASA'S 2011 STRATEGIC GOAL 2.3 ESPECIALLY FOR PLANETARY (AND SOLAR) SYSTEM EVOLUTION. THIS RESEARCH SUPPORTS NASA'S PLANETARY SCIENCE AND ASTROPHYSICS GOALS IN THE SCIENCE MISSION DIRECTORATE'S SCIENCE PLAN-PARTICULARLY TO UNDERSTAND THE ORIGIN AND EVOLUTION OF MINOR BODIES IN THE SOLAR SYSTEM AS WELL AS INFERRING THE PRESENCE OF EXOPLANETS AND THEIR PROPERTIES.