An accurate knowledge of spatial and temporal current variations in the open ocean and in coastal waters is essential for a variety of applications, such as scientific studies on the dynamics of fronts, eddies, and internal waves, the monitoring of morphodynamic changes in coastal regions, risk management for coastal and off-shore structures, and ship operations. While point measurements can be obtained in many ways, only radar techniques permit synoptic measurements of surface current fields within areas of hundreds of square kilometers. After the well-established shore-based HF radar (high frequency radar) technique, a new satellite-based technique called along-track interferometric synthetic aperture radar (along-track InSAR) will become available in the near future.

A first demonstration of current measurements from space by along-track InSAR was given with Shuttle Radar Topography Mission (SRTM) data from February 2000. An SRTM-derived current field off the coast of the Netherlands was shown to be consistent with numerical circulation model results; an accuracy of 0.1 m/s was obtained at an effective spatial resolution on the order of 1 km. Given the fact that the SRTM instrument on space shuttle Endeavour had not been designed for current measurements, this was a quite impressive and encouraging result.

In early 2009, the experimental along-track InSAR mode of the German satellite TerraSAR-X (in orbit since June 2007) will become available for current measurements anywhere in the world. According to theoretical studies, the data quality will still be suboptimal, but superior to the SRTM results and sufficient for many applications. We are planning to establish state-of-the-art receiving and processing capabilities for along-track InSAR data products from TerraSAR-X and other satellites at CSTARS.

Reference:
[1] Romeiser, R., H. Breit, M. Eineder, H. Runge, P. Flament, K. de Jong, and J. Vogelzang, Current measurements by SAR along-track interferometry from a space shuttle, IEEE Trans. Geosci. and Remote Sensing, 43, 2315-2324, 2005.