The Geodynamics Experimental Ocean Satellite (Geos 3), launched April 9, 1975, has provided over 3½ years of data useful for the determination of oceanographic and geophysical parameters. The quality and quantity of the data caused a rapid shift in emphasis from the experimental stage to an applications orientation, including areas of application not originally anticipated. Brief descriptions of the project organization, experiment package description, mission profile, and highlight results are presented to serve as background material for the detailed results presented in this special volume.