Abstract. Aperture synthesis is an attractive alternative to conventional passive microwave imaging systems for remote sensing applications. Whenever a high spatial resolution is desired or the imaging process should work like an optical camera or when microwave remote sensing in the near field has to be distance adaptive, conventional systems cause a lot of problems. However, aperture synthesis for practical applications requires a lot of single receivers and correlators. This can cause other problems because of the large number of possible imperfections. To get an estimation of such effects, the imaging expressions for the aperture synthesis principle are developed for the near-and far-field conditions of a real system. To support the theory and to get an estimation of the feasibility of this imaging method, a simple experimental system is described and experimental results of high spatial resolution for the near and far field are shown. For the near-field case a special reconstruction algorithm was developed and is described theoretically and validated by the experiments. A discussion of the temperature resolution of aperture synthesis concludes the paper.
The launch of the Soil Moisture and Ocean Salinity (SMOS) mission on 2 November 2009 marked a milestone in remote sensing for it was the first time a radiometer capable of acquiring wide field of view images at every single snapshot, a unique feature of the synthetic aperture technique, made it to space. The technology behind such an achievement was developed, thanks to the effort of a community of researchers and engineers in different groups around the world. It was only because of their joint work that SMOS finally became a reality. The fact that the European Space Agency, together with CNES (Centre National d'Etudes Spatiales) and CDTI (Centro para el Desarrollo Tecnológico e Industrial), managed to get the project through should be considered a merit and a reward for that entire community. This paper is an invited historical review that, within a very limited number of pages, tries to provide insight into some of the developments which, one way or another, are imprinted in the name of SMOS.
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