Research on a Method for Simulating Multiview Ocean Wave Synchronization Data by Networked SAR Satellites

Yong Wan,Xiaolei Shi,Yongshou Dai,Xiaoyu Zhang

doi:10.3390/jmse7060180

Abstract

It is expected that the problem of the azimuth cutoff wavelength in single-satellite synthetic aperture radar (SAR) observations can be solved by means of the cooperative observation of networked SAR satellites. Multiview SAR wave synchronization data are required in the process. However, most of the current orbiting satellites are geosynchronous orbit satellites; the simultaneous observation by multiple SARs in the same sea area cannot be achieved, and multiview synchronization data cannot be obtained. Therefore, this paper studies the simulation of the multiview SAR wave synchronization data. Ocean wave spectra were simulated by using the Pierson Moskowitz (PM) spectrum. The Monte Carlo method was used to simulate two-dimensional (2D) ocean surfaces at different wind speeds. The two-scale electromagnetic scattering model was used to calculate the ocean surface backscattering coefficient, and the time-domain echo algorithm was used to generate echo signals. The echo signals were processed by the Range–Doppler (RD) imaging algorithm to obtain ocean SAR data. Based on the obtained single-SAR wave data, networked satellites consisting of three SARs were simulated, and the SAR wave data were synchronized. The results show that when SARs are used to observe the same sea area from different observation directions, the clarity of the wave fringes in the SAR images are different. For different azimuth angles, the degrees of azimuth cutoff are different. These results reflect the influences of different degrees of azimuth cutoff on SAR images. The simulated wave synchronization data can be used as the basic data source for subsequent azimuth cutoff wavelength compensation.

Highlights

Ocean waves are small-scale wind-gravity waves that occur on ocean surfaces, including sea and swell, and are an important ocean dynamic process
The ocean surface area size is 1024 m × 1024 m, which can be adjusted according to the actual needs, but it is recommended to set the area size to the power of two to facilitate the subsequent fast Fourier transform (FFT)
Since the wave propagation direction is perpendicular to the wave stripe, the wave propagation direction in the figure is 45◦, which is in accordance with the initial input conditions of the simulation

Summary

Introduction

Ocean waves are small-scale wind-gravity waves that occur on ocean surfaces, including sea and swell, and are an important ocean dynamic process. The common methods for obtaining ocean wave information include numerical models, field observations, and remote sensing observations. The model can obtain the results of ocean wave parameters of long-term sequences, it is affected by multiple conditions, such as initial condition settings, observation data assimilation and water depth. Field observations mainly consist of sea state measurements from buoys [2]. Buoys can verify the ocean wave parameters obtained by numerical models and remote sensing [4]. Remote sensing obtains the sea state by means of a synthetic aperture radar (SAR), altimetry and scatterometry. Compared with numerical models and in situ buoy measurements at a single location, SARs are effective and of great interest because of the high spatial resolution and the almost instantaneous observation potential of large ocean areas [8]. This paper intends to use SARs to achieve the observation of ocean waves

Results

Discussion

Conclusion