KaRIn, the Ka-Band Radar Interferometer of the SWOT Mission: Design and in-Flight Performance

The Surface Water and Ocean Topography (SWOT) mission was recommended by the 2007 National Research Council Decadal Survey to expand on previous altimetry missions such as TOPEX/Poseidon. Utilizing wide-swath altimetry technology, SWOT aims to achieve complete coverage of the world’s oceans and freshwater bodies through high-resolution elevation measurements. SWOT received approval for implementation in 2016, it was ultimately launched in December 2022, and it is currently delivering preliminary data to the public. The primary instrument in SWOT is the Ka-band Radar Interferometer (KaRIn), which utilizes Jet Propulsion Laboratory (JPL)-developed radar interferometry technology to measure ocean and surface water levels with unprecedented accuracy. This article focuses on the challenges in designing, testing, and finally commissioning in flight a complex instrument such as KaRIn. We also present preliminary flight performance and compare it with ground measurements and simulations. Our analysis indicates that KaRIn meets or exceeds all its requirements, but it has also revealed several interesting and unexpected observations, offering just a glimpse of future scientific discoveries that KaRIn will enable.