The 2012 Division Outstanding Young Scientists Awards is awarded to Xavier Collilieux for his significant contributions towards improved methods and procedures in computing global terrestrial reference frames and for his studies of surface loading effects therein.
Xavier Collilieux has distinguished himself as a leading researcher in developing refined methods for realizing global terrestrial reference frames, aimed mainly towards an improved International Terrestrial Reference Frame (ITRF). He has contributed significantly in understanding how best to minimize aliasing of station-dependent environmental loading variations into global Helmert alignments to form long-term frames. This has allowed for the generation of station position time series that can be used more reliably for numerous high-accuracy geophysical applications. Without exaggerating, Collilieux has become the leading expert in providing GPS and other position time series for the benefit of the work of many other researchers. In the process he has clarified the degree to which current space geodetic measurements are consistent with loading models and GRACE-inferred displacements. In addition, Collilieux has studied various aspects of the quality of the geodetic parameters delivered by each of the observing methods, such as the agreement of geocenter motions from satellite laser ranging with load model predictions and the consistency of height measurements among the techniques.