Satellite Remote Sensing: Salinity Measurements

Emerging new technology and a growing scientific need for global ocean-surface salinity measurements have stimulated programs now underway to launch salinity-observing satellite sensors by the year 2010. Technical challenges for very low-noise microwave radiometers and large antenna structures are now being resolved. Salinity remote sensing is possible because the dielectric properties of seawater which depend on salinity also affect the surface emission at certain microwave frequencies. Measurements will be made in the protected 1.413 GHz astronomical hydrogen absorption band to avoid radio interference. Science needs, primarily for climate studies, dictate a resolution requirement of approximately 100 km spatial grid, observed monthly, with approximately 0.1 error on the Practical Salinity Scale (or 1 part in 10 000), which demand very precise radiometers and that several ancillary errors be accurately corrected.