Doppler Scatterometry (DopplerScatt)


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NASA’s DopplerScatt instrument (Rodriguez et al., 2018) provides simultaneous measurements of ocean vector winds and surface currents estimates over a 24-km swath. The surface currents are used to compute surface convergence and vorticity. Winds are used to investigate air-sea interaction and to estimate the wind-driven current component.

DopplerScatt uses a pencil-beam mechanically scanning antenna that measures surface radar cross sections and radial Doppler velocities that are processed to estimate ocean vector winds and currents concurrently. The instrument operates at Ka-band (35.75 GHz), allowing for a compact antenna accommodation using waveguide slot array technology (22 cm diameter) protected by the RF-transparent radome (Fig. 3.1). The antenna rotation enables wide swath coverage (24 km when flying at 28 kft) as well as looks in multiple azimuth directions allowing the recovery of vector winds and surface currents at 200 m spatial resolution. Unlike traditional scatterometers, the radar operates coherently allowing for Doppler measurements of the relative velocity between the platform and the surface. DopplerScatt includes a precision Inertial Measurement Unit (IMU) coupled with the Applanix GPS receiver which enables accurate motion compensation and removal of the platform velocity for retrieval of the surface velocity component.

DopplerScatt was developed under NASA Earth Science and Technology Office (ESTO) Instrument Incubator Program (IIP) and NASA AITT.

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