MirrorSAR: A Fractionated Space Radar for Bistatic, Multistatic and High-Resolution Wide-Swath SAR Imaging

Abstract

This paper introduces the new and highly capable concept of a fractionated MirrorSAR which has the potential to serve a wide range of Earth observation applications with unique remote sensing products. The proposed system is based on a set of mutually separated transmitter and receiver satellites. As opposed to previously published bi- and multistatic SAR systems, the receiver satellites are considerably simplified, as their main functionality is reduced to a kind of microwave mirror (or space transponder) which merely routes the radar echoes towards the transmitter(s). The routed signals from one or more receiver satellites are then coherently demodulated within the transmitter(s) by using the same oscillator that had been used for radar pulse generation. By this, one can avoid the necessity of a bidirectional phase synchronization link between the transmitter and receiver as currently employed in TanDEM X. The joint availability of all receiver signals in a centralized node offers moreover new opportunities for efficient data compression, as the multistatic radar signals from close satellite formations are characterized by a high degree of mutual redundancy. As the receiver satellites become rather simple in this approach, it becomes possible to scale their number without cost explosion, thereby paving the way for novel applications like multi-baseline SAR interferometry and single-pass tomography. Several additional opportunities make such a configuration even more attractive. First, the separation between the transmitter and receiver satellites enables a new approach to image ultra-wide swaths with very high resolution, thereby overcoming an inherent limitation of conventional monostatic SAR systems. Second, the system capabilities can be further scaled by adding multiple transmitters which enable several new MIMO-SAR modes including adaptive and hybrid MIMO-SAR imaging and MIMO-SAR tomography. A further advantage arises from the separation of the transmitter and receiver front-ends, which will reduce losses and allows for a significant reduction of the peak power by employing a highly efficient frequency-modulated continuous wave illumination (FMCW).