In late autumn 1993, a conference on Satellite Altimetry and the Oceans was held in Toulouse, France. The TOPEX/Poseidon satellite had begun the second year in orbit, and all indications were that the data quality was beyond expectations. During the final address at the conference, Carl Wunsch recounted, among other things, the technical progress of satellite altimetry over nearly two decades, wherein the accuracy had improved a 100-fold. He emphasized that this success resulted from early recognition that fundamental “zeroth-order” scientific impact could be derived from planning and implementing requisite technology development. The same has held true for technology to measure winds, sea surface temperature (SST), ocean color, and the gravity field from space, he pointed out, and then asked “What are we overlooking? What new technological challenges are there for zeroth-order impact on the knowledge of the ocean?” The purpose of this paper is to suggest that measuring the global surface salinity field from satellite is the next challenge.