A transponder-based motion compensation approach for near-space passive radars

Near-space platforms defined as the aerocrafts flying in the space region between 20km and 100km which is above the storms and not constrained by orbital mechanics like satellites or high fuel consumptions like airplanes, they can stay at a specific site almost indefinitely to provide a persistent coverage. Although current spaceborne and airborne synthetic aperture radar (SAR) systems have playing an important role in various remote sensing applications, they cannot provide a staring presence on a timescale of days, weeks, or months over a selected target or area of interest. To get around these disadvantages, near-space passive bistatic SAR which involves a passive receiver placed inside a near-space aerocraft in conjunction with some opportunistic illuminators, is recommended for persistently remote sensing applications; however, effective motion compensation is required. As such, this paper presented one transponder-based motion compensation approach. The system configuration and corresponding signal processing algorithm are detailed. Furthermore, several possible error sources and their effects on motion compensation are also investigated.