High-Squint Imaging Method for Spaceborne Bistatic SAR Considering Orbit Curvature Effect

Bistatic Synthetic Aperture Radar (BiSAR) is an advanced radar imaging system in which the transmitter and receiver platforms are positioned at distinct spatial locations. This separated transmit–receive architecture enables coordinated observation of the target scene. In particular, the highly squinted spaceborne bistatic configuration offers advantages in multi-angle observation, overcoming the insensitivity of conventional spaceborne interferometric SAR (InSAR) to north–south surface deformations, thereby enabling efficient and high-precision measurement of global three-dimensional (3D) surface deformations, which holds significant engineering application value. Focusing on the highly squinted spaceborne BiSAR imaging geometric model, this paper proposes a novel highly squinted imaging method based on a high-order model. Traditional imaging algorithms are founded on straight-line models and employ the method of series reversion (MSR) to achieve imaging. In contrast, the proposed method is specifically tailored to the highly squinted bistatic observation geometry, fully accommodating orbital curvature effects while simultaneously resolving the imaging challenges posed by two-dimensional (2D) spatial variations of imaging parameters. In this method, control points are judiciously distributed within the observation scene, and the imaging parameters are solved via high-order polynomial fitting. Based on this foundation, the 2D spectrum expression for the highly squinted bistatic configuration is rigorously derived, together with the frequency-domain resampling mapping relation that compensates for the 2D spatial variation of imaging parameters, thereby achieving full-scene high-accuracy focused imaging. The proposed approach broadens the applicability of conventional straight-line-model-based algorithms and is well suited for highly squinted bistatic SAR imaging. The validity of the method is ultimately demonstrated via extensive simulation experiments and thorough performance evaluations.