The Ka-band Radar Interferometer (KaRIn) is an altimeter used to measure water surface heights and one instrument aboard the NASA/CNES (Centre National d'Etudes Spatiales)/CSA (Canadian Space Agency)/United Kingdom Space Agency Surface Water and Ocean Topography (SWOT) satellite. KaRIn is a near-nadir (+/- 2.7° look angle) swath-based instrument that measures the highly reflective water surface. The instrument acquires measurements at Ka-band (35.75 GHz) with two Ka-band synthetic aperture radar (SAR) antennae at opposite ends of a 10-m boom. The KaRin instrument consists of the KaRIn Digital Electronics Subsystem (KDES), the Radio Frequency Unit (RFU), the High Power Amplifier (HPA), and the Deployable Antenna Assembly.