| Distributed Satellites Interferometric Synthetic Aperture radar (DSInSAR) avoids time decorrelation between interfeometric signals and improves the topographic measure sensitivity owing to large baseline formed among satellites. The technique acquiring high precision digital elevation model (DEM) by the system has been hot researching topic in recent years. Compared to conventional InSAR system, DSInSAR system has some new characteristics, such as bistatic radar, squint-model, baseline instability and large baseline and so on.Baseline parameter is one of the pivotal factors to height precision. And in order to ensure the height precision, high precision of baseline's length is very important, In this paper we mainly aim to Cross Track Interferometric SAR (CT-InSAR), which is effected by baseline severely among the Distributed Satellites System. This paper does some researches on the factors, which affect the DEM precision, especially the baseline factor. And do some analysis, which affect the baseline stabilization. Then the paper provides the mixed ranging technology to resolve the baseline stabilization problem.In this paper, the main contents are as follows. (1) From the height error formula, the optimized length of baseline is derived. And according to the height precision, the height sensitivity and the ambiguity function requirements to baseline precision, the relation between maximum baseline and optimized baseline is concluded. (2) Using the elliptical configuration, the three satellites CT-InSAR's baseline design is constructed. (3) Analyze the baseline precision's affection to DEM precision and do some analysis on baseline stability. (4) Do some researches on the wireless ranging, and then provide the mixed ranging technology to resolve the baseline stabilization problems. And according the system requirements, the detail design is provided. (5) Advance a fast FFT demodulation, which can conquer the trace error, which is brought by the Doppler shift.
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