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Simultaneously real-time monitoring for several distributed areas of interest is getting important in many applications. Such as security guarantee system during Olympic Games and brushfire monitoring for power grid. However, current remote sensing systems can hardly meet such steep demands. In this paper, we introduce a brand new system of Balloon SAR with Multi-spotlight illuminate mode. The new system is qualified with high resolution imaging ability for several flexible areas. Meanwhile, real time monitoring for long time duration is available here.

A novel ground moving target detection and imaging model called Near-Space Slow SAR (NSS-SAR) is introduced in this paper. It is not only effective for fast-moving targets but also slow-moving and micro-moving targets, which is hardly possible for conventional airborne and spaceborne SAR. Meanwhile, this model only needs mono-channel to distinguish Doppler signature of moving targets from the competing ground clutter returns via Doppler filtering. In addition, following analysis demonstrates that the NSS-SAR also has the potential to simultaneously achieve high-resolution and wide-swath (HRWS) imaging. Simulations given at the end of this paper verify the validity of the new NSS-SAR mono-channel moving target detection and imaging model.

Near space slow speed SAR owns the ability of sustainable and large-scene imaging. However, the output speed of azimuth image is slow due to the slow speed motion, which is a disadvantage for some applications. In this paper, the terrain observation by progressive scans (TOPS) mode is applied in near space slow speed SAR, and the signal properties are analyzed.

Due to left/right Doppler ambiguity, and the small difference in Doppler frequencies of adjacent points in flight direction, conventional monostatic SAR can not be used for forward-looking imaging. Then bistatic SAR with transmitter and receiver mounted on different platforms is coming into the eyes of researchers. In this paper, the feasibility of forward-looking imaging using airborne bistatic SAR is studied. Firstly, the potential two-dimension resolution ability of bistatic SAR for forward-looking imaging is discussed from the aspect of iso-Doppler and iso-range line. Then the airborne bistatic SAR experiment using a side-looking airborne transmitter and a forward-looking airborne receiver is described, and the preliminary results are presented. To the authors' knowledge, this is the first bistatic forward-looking SAR experiment in the world that both transmitter and receiver are mounted on aircraft platforms.

Pulse repetition frequency (PRF) redundancy exists in near space slow speed SAR due to slow speed motion, and then the beam can point to different scene at the same position. Hence, the large scene imaging can be realized. However, the range migration and azimuth resolution is azimuth variant, which makes the imaging difficult. In this paper, imaging mode of near space slow speed SAR is presented, and the variable aperture BP imaging algorithm is proposed. Simulations are given to verify the effectiveness of the imaging scheme.