SEARCH AND DISCOVERY IN THE TRANS-NEPTUNIAN SOLAR SYSTEM USING THE DARK ENERGY SURVEYWITH THE RECENT SUCCESS OF THE NEW HORIZONS MISSION AND THE HYPOTHESIS OF A VERY DISTANT PLANET NINE INTEREST IN THE TRANS-NEPTUNIAN SOLAR SYSTEM IS AT AN ALL-TIME HIGH. THIS PROPOSAL DESCRIBES AN OPPORTUNITY TO LEVERAGE AN EXTRAORDINARY DATA SET TO SHED NEW LIGHT ON THIS POORLY UNDERSTOOD REGION. THE DATA COME FROM THE DARK ENERGY SURVEY (DES) WHICH HAS BEEN AWARDED 525 NIGHTS OVER 5 YEARS (2013-2018) ON THE 4-METER BLANCO TELESCOPE AT CERRO TOLOLO IN CHILE. DES CONSISTS OF TWO INTERLEAVED SURVEYS: A WIDE SURVEY THAT IS IMAGING 5000 SQ. DEG. IN FIVE COLORS TO A LIMITING R-BAND MAGNITUDE OF ~23.8 AND A SUPERNOVA SURVEY THAT OBSERVES 30 SQ. DEG. APPROXIMATELY WEEKLY FOR SIX MONTHS EACH YEAR AT A DEPTH UP TO R~24.5. THE COMBINATION OF AREA AND DEPTH THAT MAKES DES THE WORLD S FOREMOST ONGOING COSMOLOGICAL SURVEY ALSO MAKES IT IDEALLY SUITED TO DISCOVER AND STUDY HUNDREDS OF NEW TRANS-NEPTUNIAN OBJECTS (TNOS). DES S BROAD OFF-ECLIPTIC COVERAGE ALSO MAKES THIS SURVEY PARTICULARLY SENSITIVE TO THE DYNAMICALLY DISTURBED HOT TNO POPULATIONS THAT OCCUPY HIGHER-INCLINATION ORBITS. THESE OBJECTS ENCODE THE HISTORY OF THE SOLAR SYSTEM S BIRTH ENVIRONMENT AND THE FORMATION AND MIGRATION HISTORIES OF THE GIANT PLANETS. THE MOST DISTANT TNOS DISPLAY AN ALIGNMENT IN ORBITAL AND PHYSICAL SPACE THAT MAY POINT TO THE EXISTENCE OF A DISTANT SUPER-EARTH SUCH AS THE PLANET NINE (P9) RECENTLY PROPOSED BY BATYGIN&BROWN (2016). THIS HYPOTHESIS CAN BE DECISIVELY TESTED WITH OUR DATA. WE WILL DO SO BOTH THROUGH A DIRECT SEARCH FOR P9 AND THROUGH THE DISCOVERY OR EXCLUSION OF DYNAMICALLY RELATED OBJECTS PREDICTED BY THE THEORY SUCH AS A POPULATION OF HIGH INCLINATION CENTAURS AND ADDITIONAL DISTANT ALIGNED OBJECTS. OUR DIRECT SEARCH WILL COMPLEMENT THE RECENT ANALYSIS BY FIENGA ET AL. (2016) WHICH USED THE PRECISE MEASUREMENTS OF THE DISTANCE TO SATURN OBTAINED BY NASA S CASSINI SATELLITE OVER THE PAST DECADE. THEIR ANALYSIS EXCLUDES A BROAD RANGE OF POSSIBLE P9 POSITIONS NEAR PERIHELION BUT SHOWS THAT A SMALL REGION CORRESPONDING TO A P9 TRUE ANOMALY NEAR 120 DEGREES IS FAVORED OVER THE NULL HYPOTHESIS. THIS FAVORED REGION LIES IN THE MIDDLE OF THE DES SURVEY FOOTPRINT. THE PI LEADS THE TRANSIENTS AND MOVING OBJECTS SCIENCE WORKING GROUP WITHIN DES AND HAS DISCOVERED ALL ~50 OF THE TRANS-NEPTUNIAN OBJECTS FOUND BY DES TO DATE. AMONG THESE OBJECTS IS ONE OF THE SIX OBJECTS MOST DISTANT TNOS WHOSE ALIGNED ORBITS MOTIVATED THE P9 HYPOTHESIS. THIS SEARCH BEGAN IN THE DES SUPERNOVA SURVEY FIELDS WHOSE REGULAR TEMPORAL CADENCE SIMPLIFIES THE PROBLEM OF CONNECTING OBSERVATIONS OF FROM DIFFERENT EPOCHS. WE HAVE BEGUN TO EXTEND THE SEARCH TO THE WIDE SURVEY WHOSE SPARSER TEMPORAL CADENCE LEADS TO A MORE CHALLENGING COMBINATORIC PROBLEM. A PROTOTYPE SEARCH USING ONLY 100 SQ. DEG. OF DATA (2% OF THE FULL SURVEY AREA) FROM THE 2013-14 SEASON RESULTED IN OVER A DOZEN NEW TNOS AND GIVES US CONFIDENCE THAT THE STRATEGY WE INTEND TO DEPLOY AT SCALE FOR THE FULL 5000 SQ. DEG. FIVE-YEAR WIDE SURVEY WILL BE SUCCESSFUL. THIS PROPOSAL WILL RESULT IN MULTIPLE-OPPOSITION ORBITS FOR SEVERAL HUNDRED NEW PRIMARILY HIGH-INCLINATION TNOS COMPLETE WITH MULTICOLOR PHOTOMETRY AND A WELL-CHARACTERIZED SELECTION FUNCTION. THESE DATA WILL PROVIDE US WITH AN OPPORTUNITY TO REASSESS THE DYNAMICAL HISTORY OF THE SOLAR SYSTEM. THIS PROJECT WILL INCLUDE A THEORETICAL ANALYSIS TO PROVIDE A DYNAMICAL INTERPRETATION OF THE DATA WITH A FOCUS ON EVOLUTIONARY SCENARIOS THAT PRODUCE THE OBSERVED POPULATIONS OF TNOS. WE ALSO OUTLINE A PROGRAM TO ALLOW CITIZEN SCIENTISTS TO SEARCH FOR TNOS IN PUBLIC DES DATA. THIS PROPOSAL REQUIRES NO MODIFICATIONS TO DES S TIME ALLOCATION SURVEY STRATEGY OR DATA REDUCTION PIPELINES BUT WILL GREATLY AMPLIFY THE SCIENTIFIC RETURN ON THIS DATA SET.