Ocillator clock drift compensation in bistatic interferometric SAR

Bistatic interferometric SAR systems like e.g. the Interferometric Cartwheel are characterized by spatially separated transmitters and receivers. Such systems pose much higher requirements on the stability of the local oscillator used for demodulation than SAR systems that are used for imaging only. Apart from the higher cost of such an oscillator it is questionable whether oscillators with sufficient accuracy are technically feasible in space at all. The paper establishes some strong interferometric requirements on the oscillator clock stability in bistatic SAR configurations from the consequences of oscillator phase errors in the SAR interferograms. A new method for the compensation of oscillator phase errors is presented that allows the use of standard oscillators. The method consists of additional synchronization signals exchanged between the satellites and an interferometric processing scheme. The presented technique compensates any phase drifts caused by oscillator drifts and by relative motion of the receiving satellites.