Task Simulation For An Ocean Salinity Mission With One-dimensional Synthetic Aperture Microwave Radiometer At L Band

About 71% of the earth is covered by ocean and the sea surface salinity is very important to weather forecast and climatic change. Its distribution and variation is critical to study the ocean climate system. But the development of remote sensing for sea surface salinity is too insufficient to satisfy the needs of application. Compared with the field measurements such as salinity sampling vessel, the space remote sensing can achieve large area and long time observation, which is essential to the engineering construction,resource development and scientific research.Under such circumstances, the National Space Science Center proposed the concept of a new type of combined active and passive sensor for soil moisture and ocean salinity measurements. The passive part of the instrument can be realized by a push-broom radiometer worked in L band with the features of high sensitivity and high stability, which can provide the high-accuracy observation to the distribution of sea surface salinity. The active part of the instrument can be realized by a scatterometer to get the information of sea surface roughness, which is used to improve the accuracy of salinity retrieval. The synthetic aperture radiometer is the key module of the whole instrument, which works at 1.1435 GHz. 8 antennas are arranged in a one-dimensional array which can reduce the system complexity compared with SMOS and improve the spatial resolution and swath compared with Aquarius.In this thesis, a task simulation system is built with Matlab to simulate the system structure and operation of the space borne one-dimensional synthetic aperture radiometer. This system mainly consists of three modules: target modeling module, radiometer simulation module and image reconstruction module. The target modeling module aims to simulate the process in which the satellite obtains the image of brightness temperature. The input parameters are the sea surface temperature, sea surface salinity, wind speed, etc. And the module can export the brightness temperature observed by antennas in any orbital position. The radiometer simulation module simulates the sampling process of one-dimensional synthetic radiometer in frequency domain. It can calculate visibility function according to the principle of synthetic aperture radiometer and one-dimensional antenna array. The image reconstruction module realizes the transformation from visibility function to brightness temperature using a new algorithm according to the feature of one-dimensional array and its performance can meet the needs of the designThe effects of the external error sources, including sun, moon and galaxy, on biases in brightness temperature are also evaluated using the simulation system. First, the model to the external error sources’ location in the field of view is built according to the astronomic knowledge and orbit parameters. Second, using their brightness temperature and the principle of location variation in the field of view, simulate the annual variety regulation of error to the and caused by galaxy, moon and sun.The work in this thesis will provide a simulation platform for the following design and optimization to the synthetic aperture radiometer. In addition, it can provide valuable references for hardware system design and salinity retrieval.