Analysis of the virtual baseline of cluster SAR satellites

The change of the virtual baseline (equivalent baseline or projection of baseline) of cluster SAR satellites is analyzed when the constellation is circling around the Earth and at the same time the satellites are rotating around the center. This paper provides the assessment of baseline error, which influence on the precision of height measurement in the across-track interferometric mode. The relevant mathematical model is built and simulation analysis as well as the curve of height error is presented. Numerical results confirm theoretical analysis and quantitatively show that the virtual baseline is varying periodically with the latitude of the nadir of the "virtual" satellite, the constellation circling angle, the linear velocity of the Earth surface, and the angle between the projection of satellite orbit on the Earth surface and latitude circle, etc. The baseline error must be taken into account in the process of InSAR imaging and can be compensated by using the formulae derived in this paper to recover digital elevation models (DEM\´s) accurately