THE NEW HORIZONS (NH) SPACECRAFT FLEW PAST JUPITER S INNERMOST GALILEAN SATELLITE IO IN 2007 ON ITS WAY TO PLUTO AND THE KUIPER BELT WHILE THE NH LONG RANGE RECONNAISSANCE IMAGER (LORRI) AND THE MULTISPECTRAL VISUAL IMAGING CAMERA (MVIC) OBTAINED A UNIQUE AND DRAMATIC TIME SERIES OF HIGH SPATIAL RESOLUTION IMAGES CAPTURING THE ERUPTION OF TVASHTAR A PELE-CLASS VOLCANIC PLUME LOCATED AT +62 DEG LATITUDE AND 237 DEG E LONGITUDE. DURING THE FLYBY THE SUN-IO-NH SOLAR PHASE ANGLE VARIED FROM 35 TO 154 DEG WHILE IO MADE OVER 2 FULL REVOLUTIONS RELATIVE TO THE SPACECRAFT CAPTURING VIEWS OF THE PLUME FROM MULTIPLE ASPECTS AND PHASE ANGLES. THE PLUME BRIGHTNESS WAS OBSERVED TO INCREASE BY OVER AN ORDER OF MAGNITUDE DURING THIS PERIOD. SUCH AN EXTREME RISE IN BRIGHTNESS HAS NOT BEEN OBSERVED FOR ANY EXTRATERRESTRIAL PLUME BEFORE. IN THE PAST TVASHTAR S ERUPTIVE MODE HAS BEEN ON SEPARATE OCCASIONS CHARACTERISTIC OF A FIRE FOUNTAIN AND A VENTING LAVA LAKE. ALTHOUGH A FORTUITOUS CHANGE IN ERUPTIVE MODE DURING THE NH FLYBY REMAINS A POSSIBILITY IT IS MORE LIKELY THAT THE CHANGING SCATTERING GEOMETRY EXPLAINS THE LARGE CHANGE IN PLUME BRIGHTNESS WITH SUPERPOSED SESSIONS OF IRREGULAR PULSING THAT CHARACTERIZE THE ERUPTIVE MODE. POST-VOYAGER OBSERVATIONS OF THE PLUME HAVE GENERALLY INDICATED A REGULAR PLUME APPEARANCE. HOWEVER THE OBSERVATIONS OF THE BEHAVIOR AND DURATION OF IO S VOLCANIC ERUPTIONS ARE SPARSE SO THE PROCESSES THAT CONTROL THE VOLCANIC ERUPTIONS ARE POORLY UNDERSTOOD. THERE IS THUS A NEED TO LEARN MORE ABOUT THE VOLCANIC PROCESSES OF IO S PELE-TYPE PLUMES. THE DATA COLLECTED FOR TVASHTAR DURING THE NH FLYBY PROVIDE AN EXCELLENT OPPORTUNITY TO DO SO A PELE CLASS (EXPLOSIVE) PLUME. CHARACTERIZING THE STRUCTURE OF THE DUST EMBEDDED IN THE PLUME MAY HELP TO CHARACTERIZE OR CONSTRAIN THE ERUPTIVE PROCESS OF ITS FORMATION. AGGREGATES TEND TO BE STRONGLY FORWARD SCATTERING. IF THEY DOMINATE THE DUST IN IO S PLUME THEY WOULD RESULT IN A SMOOTH MONOTONIC RISE TO THE BRIGHTNESS OF THE PLUME DURING THE FLYBY AS THE SUN-IO-SPACECRAFT SCATTERING ANGLE GRADUALLY DECREASES. MEANWHILE FLUCTUATIONS IN THE BRIGHTNESS WOULD BE ATTRIBUTABLE TO VENT ACTIVITY. THE FLYBY WOULD THUS HELP TO CHARACTERIZE THE VOLCANIC ACTIVITY THROUGH DOCUMENTING THE UNSTEADY FLUCTUATIONS OBSERVED AGAINST THE OVERALL SECULAR BRIGHTNESS RISE. FOR THE FIRST TIME WITH AN EXTRATERRESTRIAL VOLCANO THE UNIQUE TIME SERIES COLLECTED BY THE UNPRECEDENTED FLYBY OBSERVATIONS WOULD HELP TO DISENTANGLE THE PARTICLE AGGREGATE AND SCATTERING PROPERTIES FROM THE ACCOMPANYING VENT ACTIVITY. FURTHERMORE FIXING THE SCATTERING PROPERTIES WOULD ALSO HELP TO CONSTRAIN THE SIMULATION OF THE GASEOUS PLUME STRUCTURE. TO ADDRESS THESE MOTIVATIONS WE PROPOSE TO INVESTIGATE TVASHTAR S BRIGHTENING DURING THE NH FLYBY WITH THE FOLLOWING OBJECTIVES: 1) EXAMINE THE CHANGE IN THE SIZE AND SHAPE OF THE TVASHTAR PLUME DURING THE JUPITER FLYBY TO CHARACTERIZE ITS SHORT-TERM VOLCANIC VARIABILITY AND ANY SIGNIFICANT VENT ELONGATION. 2) CHARACTERIZE THE STRUCTURE OF THE AGGREGATE DUST PARTICLES IN TVASHTAR S PLUME AS CONSTRAINED BY THE SECULAR CHANGE IN THE PLUME BRIGHTNESS DURING THE NH FLYBY. 3) COMPARE THE STRUCTURE OF THE TVASHTAR PLUME AGGREGATES TO THOSE OF TERRESTRIAL VOLCANOES. THIS PROPOSAL ALIGNS WITH THE OBJECTIVES OF NASA S NFDAP DATA ANALYSIS PROGRAM BY EXTENDING THE SCIENTIFIC YIELD OF THE NEW HORIZONS MISSION DURING THE IO FLYBY PHASE THROUGH BROADENING THE PARTICIPATION IN THE SCIENCE RETURN OF THAT PHASE. IT DOES THIS THROUGH THE PROPOSED ANALYSIS AND INTERPRETATION OF CALIBRATED DATA ON THE TVASHTAR ERUPTION OBTAINED BY THE LORRI AND MVIC CAMERAS DURING THE NEW HORIZONS FLYBY OF IO.