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Interferometric synthetic aperture radar data are often obtained on the basis of repeated satellite acquisitions. Errors in the satellite orbit determination, however, propagate to the data analysis and may even entirely obscure the interpretation. Many approaches have been developed to correct the effect of orbital error, which sometimes may even distort the signal. Phase contributions due to other sources, such as surface deformation, atmospheric delay, digital elevation model error, and noise, may reduce the accuracy of the orbital error estimation. Therefore, a more sophisticated approach for estimating the effect of orbital errors is required. In this paper, wavelet multiresolution analysis is employed to distinguish between the effects of orbital errors and other components (e.g., deformation signal). Next, a robust regression approach is applied to estimate the effect of orbit errors as a ramp. After describing the concept of this approach, we present a validation test using a synthetic data set. As in a real case study, the method is applied to an interferogram that was formed over the Tehran area in northern Iran. The validation test demonstrates that the orbital ramp can be estimated with a precision of 3 mm. Thus, a similar precision may be obtained in real cases such as the examined data set from over the Tehran area.