On the suitability of TerraSAR-X split antenna mode for current measurements by along-track interferometry

Latest concepts for the TerraSAR-X hardware design include the availability of a split antenna mode, in which the fore and aft halves of the SAR antenna array with a total length of 4.8 m can act as separate receiving antennas for along-track interferometry (ATI). The effective ATI time lag is 0.17 ms. We discuss in this paper whether the split antenna mode is suitable for ocean current measurements. Typical (tidal) currents in coastal areas are on the order of 1 to 2 m/s. To measure them, the ATI time lag should ideally be 20 times longer than the time lag of TerraSAR-X. Furthermore, the backscattered power from the ocean at low wind speeds can be below the noise floor of the instrument. However, the high resolution of TerraSAR-X permits averaging over many pixels to reduce noise. Simulated data products suggest that TerraSAR-X is capable of measuring currents with satisfactory accuracy at a spatial resolution of about 1 km, which is sufficient for many applications.