First Experiment With an Altimeter With Knife-Like Beam: Comparison With a Model of the Waveform of a Reflected Impulse

The altimeter is an effective instrument for remote sensing of the sea surface. Existing theoretical models of the waveform of the reflected impulse are used in the retracking algorithms for determination of the distance from radar to a scattering surface and measuring the significant wave height (SWH). These models, however, cannot be used for an altimeter with a wide antenna beam. In the latter case, the Karaev model may be used, and in this case, the waveform of the reflected impulse depends on two parameters: the SWH and the mean square slopes (mss) of the large-scale waves. In order to verify the model of the waveform of the reflected impulse, two approaches are used: a numerical experiment and an experiment on a cable car. For the measurement, a microwave radar capable of operating in altimeter mode was used. The numerical experiment simulated the measurement scheme and used a model sea wave spectrum to generate the reflecting sea surface. A comparison of the waveforms obtained during the numerical experiment and calculated using the Karaev model showed good agreement. A special procedure was suggested to form the reflected impulse in the experiment. The retracking algorithm was developed based on the Karaev model. Processing showed that all three parameters can be retrieved from such a waveform: the distance from the radar to the reflecting surface, the SWH, and the mss of large-scale waves.