EXCITATION AND DISSIPATION OF THE FREE CORE NUTATION THE FREE CORE NUTATION (FCN) IS ONE OF EARTH'S FUNDAMENTAL ROTATIONAL NORMAL MODES. IT ARISES BECAUSE THE FLUID CORE IS CONFINED WITHIN AN ELLIPSOIDAL MANTLE WHOSE ROTATION AND FIGURE AXES NEED NOT COINCIDE. IN THE TERRESTRIAL REFERENCE FRAME THE ASSOCIATED MOTION IS A NEARLY DIURNAL FREE WOBBLE (NDFW). ANALYSIS OF THE FCN (OR THE NDFW) ALLOWS US TO STUDY CERTAIN UNIQUE PROPERTIES OF THE EARTH; A CLASSIC EXAMPLE (GWINN 1986) WAS USING THE FCN TO DETERMINE THE ELLIPTICITY OF THE CORE-MANTLE BOUNDARY. OUR PROPOSAL AIMS TO IMPROVE OUR KNOWLEDGE OF THE FCN EXCITATION AND DISSIPATION AND THE GEOPHYSICAL INTERPRETATION OF FCN EFFECTS. AN IMPORTANT ASPECT IS TO IMPROVE THE MODELING OF ATMOSPHERIC AND OCEANIC CONTRIBUTIONS TO THE OBSERVED NUTATION SINCE AN IMPROPER ACCOUNTING OF THESE CAN BIAS THE RESPONSE ESTIMATES. THE MAIN GOALS OF OUR STUDY ARE (A) TO OBTAIN IMPROVED AND SELF-CONSISTENT ESTIMATES OF COMPLIANCES THAT DESCRIBE THE RESPONSE OF THE NON-RIGID EARTH TO EXTERNAL TORQUES AND GEOPHYSICAL EXCITATIONS ALONG WITH REALISTIC ERROR ESTIMATES; (B) TO CLOSE THE BUDGET OF THE EXCITATION AND DISSIPATION OF THE FCN OR TO ESTABLISH THAT THE BUDGET CANNOT BE CLOSED WITHIN UNCERTAINTIES OF GEODETIC OBSERVATIONS. OUR PRIMARY GEODETIC DATA WILL BE VERY LONG BASELINE INTERFEROMETRY (VLBI) GROUP DELAYS. THIS WILL BE ACHIEVED BY (1) INCORPORATING INTO OUR DATA ANALYSIS THE NON-GRAVITATIONAL FORCINGS FROM THE LATEST ADVANCED TIDAL AND NONTIDAL OCEANIC MODELS AND ATMOSPHERIC MODELS; (2) IMPROVING THE OCEAN TIDE MODEL AT PSI1 TIDE (CRITICAL BECAUSE ITS FREQUENCY IS SO CLOSE TO THE NDFW FREQUENCY); AND (3) ESTIMATING PARAMETERS OF THE NUTATION TRANSFER FUNCTION DIRECTLY FROM VLBI GROUP DELAYS WITHOUT RESORTING TO INTERMEDIATE TIME SERIES. IN PAST EFFORTS THE PSI1 OCEAN TIDE HAS NEVER BEEN HANDLED CORRECTLY. THIS IS BECAUSE UNLIKE ANY OTHER TIDE IT IS FORCED ABOUT EQUALLY BY THE GRAVITATIONAL TIDAL POTENTIAL AND BY RADIATIONAL EFFECTS OF THE ATMOSPHERIC TIDES. WE PROPOSE TO DETERMINE THE PSI1 BAROMETRIC PRESSURE TIDE FROM SEVERAL MODERN ANALYSES AND REANALYSES OF NUMERICAL WEATHER CENTERS. WE WILL BE GUIDED BY AN EXTENSIVE NETWORK OF BAROMETER MEASUREMENTS THAT WE HAVE BUILT UP OVER SEVERAL YEARS AND WHICH WE HAVE PREVIOUSLY USED TO STUDY THE S1 AND S2 AIR TIDES. WE WILL USE THE RESULTING AIR-TIDE MODEL TO FORCE A NUMERICAL OCEAN-TIDE MODEL THAT WE HAVE PREVIOUSLY USED TO STUDY THE S1 OCEAN TIDE. THE RESULTS COMBINED WITH THE NOMINALLY EASIER GRAVITATIONAL PART SHOULD RESULT IN A MUCH MORE REALISTIC MODEL OF THE PSI1 OCEAN TIDE THAT IS ESSENTIAL TO MITIGATE SYSTEMATIC ERRORS IN DETERMINING THE STRENGTH AND SHAPE OF THE FCN. WE WILL MODIFY THE WELL-KNOWN NEMO OCEAN MODEL TO COMPUTE OCEANIC ANGULAR MOMENTUM AND BOTTOM PRESSURE ON THE FLY AND TO STORE THESE DATA WITH A TIME RESOLUTION OF ONE HOUR. THE OCEAN DATA COMBINED WITH PRESSURE AND WIND DATA FROM NUMERICAL WEATHER CENTERS WILL SUPPLY NEW ANGULAR MOMENTUM CORRECTIONS FOR REANALYSIS OF VLBI NUTATION DATA AGAIN LEADING TO BETTER DETERMINED FCN PARAMETERS. WE ANTICIPATE THE NEMO DATA WILL BENEFIT A WIDE RANGE OF EARTH SCIENCE STUDIES NOT JUST OUR OWN. WE PROPOSE TO REANALYZE VLBI GROUP DELAYS FROM 1984 THROUGH PRESENT. WE WILL FIT PARAMETERS OF THE MODEL THAT RELATE THE OBSERVED SPECTRUM TO THE EXTERNAL GRAVITATIONAL EXCITATION EXERTED BY THE MOON SUN AND PLANETS AND TO INTERNAL EXCITATIONS CAUSED BY THE OCEANIC AND ATMOSPHERIC DYNAMICS. THE PARAMETERS OF THE MODEL WILL INCLUDE COMPLIANCES SUCH AS DYNAMIC ELLIPTICITY OF THE WHOLE EARTH AND THE CORE COMPLEX ELASTIC COMPLIANCES COUPLING AT THE CORE-MANTLE BOUNDARY AND OTHER PARAMETERS. WE WILL INVESTIGATE THE POSSIBILITY OF INCLUDING AD HOC EXCITATIONS TO EXPLAIN THE RESIDUAL SPECTRUM. FINALLY WE WILL FIT PARAMETERS OF THE MODEL DIRECTLY TO VLBI GROUP DELAY WITHOUT USING AN INTERMEDIATE SPECTRUM. WE WILL PERFORM A THOROUGH ERROR ANALYSIS AND DETERMINE REALISTIC UNCER