Study On Multi-baseline Height-measure And Formation Optimization Methods Of Spaceborne InSAR

In InSAR system, multi-baseline forms more than one Interferometric channel, which offers more information about the scene compared to the single-baseline system. In this way, multi-baseline system breaks some restrictions of single-baseline as well as improves height-measure accuracy. The traditional spaceborne multi-pass mode decreases time coherence coefficient, which reduces the height-measure accuracy. Distributed spaceborne InSAR system is composed of several small satellites, which is regarded as a suppositional satellite. It can obtain scene information at the same time and improves signal coherence coefficient. Its baselines can be optimized at a time and height-measure accuracy is improved finally. Multi-baseline Interferometric height-measure methods and formation optimization methods are presented in this paper.Height inversion equation is derived firstly based on the three-dimensional geometry of spaceborne InSAR system. But some parameters such as the range between the slave satellite and the target, the dihedral angle between the range-height plane and orbit plane can not be measured accurately. So a single-baseline height-measure method based on Doppler equation is introduced subsequently. Then close-form solution is derived and accuracy analysis is made simultaneously. Afterwords, an iteration method is presented.Distributed spaceborne InSAR system has more than one baseline. Multi-baseline offers the difference of the interferometric phases which reflects the relative location of the targets. According to this characteristic, a multi-baseline InSAR height-measure approach without ground control points is proposed. Multi-baseline can also offer additional interfeometric phase, based on which a data fusion method is researched. Moreover, accuracy analysis is made from the multi-baseline location equations and the multi-baseline accuracy model is built finally.Based on the multi-baseline accuracy model, two formation optimization methods are proposed. The first method has two steps. At first, one baseline is optimized based on the single-baseline accuracy model and fixed. Then the look angles of the second baseline is designed based on the multi-baseline accuracy model. In the second method, six orbit parameters are designed by generic algorithm, which is also based on the multi-baseline accuracy model.