Wide-Swath Ocean Current Measurement Based on MIMO Along-Track Interferometry SAR

This article proposes a configuration for a multiple input-multiple output (MIMO) along-track interferometry (ATI) synthetic aperture radar (SAR) satellite system designed for measuring ocean surface velocity vectors. The satellite system consists of a main satellite and at least two secondary satellites. The main satellite is equipped with dual antennas for transmitting and receiving echoes, while the secondary satellites are equipped with single antennas for receiving echoes. Based on the configuration, we explore key issues related to MIMO ATI SAR for measuring ocean surface velocity vectors to form a comprehensive solution. The issues include the current measurement principle, methods for assessing velocity vector accuracy, optimal baseline determination, carrier frequency selection, echo separation methods, and sources of phase error. The corresponding methods are derived in this article to address the challenges posed by the geometry of bistatic observations in beam steering and digital beamforming (DBF) processing. In addition, a system parameter design method based on optimizing ocean surface velocity measurement accuracy is proposed, eliminating the need for repeated trade-offs on individual parameters. Finally, the article presents an example of a high-precision wide-swath ocean surface velocity vector measurement system based on the configuration. This system achieves an ocean surface velocity accuracy of 3 cm/s, a swath coverage of 200 km, and a product resolution of $1\times 1$ km2 in wind speeds above 3 m/s.