A first bistatic airborne SAR interferometry experiment - preliminary results

Here are described the first successes in obtaining bistatic cross-platform interferograms from a two aircraft SAR acquisition campaign performed in February 2003 by the DLR and ONERA using their E-SAR and RAMSES facilities. The main challenging issues in the signal processing involved are the estimation and compensation of phase drift between the two radars master oscillators (bistatic receive signal is demodulated with a local oscillator which is not coherent with the transmitter one) and the determination of the relative aircraft trajectories -i.e. interferometric baseline-accurate to the millimetre (X-band wavelength is 3 cm, hence 1 mm error in relative position shifts the phase by about 10°). The high phase quality of the first interferograms obtained is encouraging, but also shows that full endo-clutter moving target indication capability in multistatic environment requires at least two passive SAR receivers in the vicinity of the transmitting active SAR system.