This paper introduces the concept of a fractionated MirrorSAR which 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 routes the radar echoes towards the transmitter. The forwarded radar signals are then coherently demodulated within the transmitter by using the same oscillator that had been used for radar pulse generation. This avoids the necessity of a bidirectional phase synchronization link as currently employed in TanDEM-X. Since the needs for fully equipped radar receivers, on-board memory and downlink are also overcome, the weight and costs of the receiver satellites can be significantly reduced. This allows for a scaling of 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 the MirrorSAR concept even more attractive. First, the separation of the transmitter and receiver front-ends reduces not only RF losses by avoiding switches and circulators, but it may also lower the peak power in the transmitter satellite by employing a frequency-modulated continuous wave (FMCW) illumination. This simplifies the design of the high-power amplifier and increases its efficiency. Second, the opportunity for continuous radar data collection enables new modes for the imaging of ultra-wide swaths with very high resolution, thereby overcoming an inherent limitation of conventional monostatic SAR systems. Third, the joint availability of all receiver signals in a centralized node offers new opportunities for efficient data compression, as the multistatic radar signals from close satellite formations are characterized by a high degree of mutual redundancy. Fourth, the use of a sufficiently separated transmitter satellite can avoid the risk for mutual illumination, which challenges the design and operation of fully-active multistatic SAR systems. Further advantages arise from the scalability and reconfigurability, which support new redundancy concepts and pave at the same time the way to new modes like MIMO-SAR tomography.

The architecture of framework to simulate Digital Beamforming reflector-based SAR systems is presented. The mai purpose of this tool is to allow the development and evaluation of DBF processing and calibration techniques unde realistic conditions. One of the main challenges is to model the antenna patterns, including their polarimetric characteristic and topography dependencies.

This paper reviews advanced SAR system architectures and modes for high-resolution ultra-wide-swath SAR imaging. The comparison includes both direct radiating array antennas and reflector-based system configurations operating in either a single-Transmit multiple-receive (SIMO) or a multiple-Transmit multiple-receive (MIMO) mode.

SAR instruments with multiple transmit/receive channels allow for a variety of operation modes. The trade-space includes the instrument and antenna parameters designed to enable various techniques (operation modes). These are utilized to achieve a required SAR performance derived from the mission and user requirements. Finding a solution in this multi-dimensional trade space of inter-dependent parameters is not trivial and often involves the compromise of parameters. This paper addresses the topic of SAR instrument design tailored to a set of operation modes. It explains the SAR techniques and reports the performance highlighting possible compromises between techniques and system efficiency.

SAR instruments with multiple transmit/receive channels allow for a variety of operation modes. The trade-space includes the instrument and antenna parameters designed to enable various operation modes. These are utilized to achieve a required SAR performance derived from the mission and user requirements. Finding a solution in this multi-dimensional trade space is not trivial and often involves the compromise of parameters. This paper addresses the topic of SAR instrument design tailored to a set of operation modes. It explains and compares the SAR techniques and gives the performance.