Abstract
This article analyzes the process of image synthesis for a formation flying synthetic aperture radar (FF-SAR), which is a multistatic synthetic aperture radar (SAR) based on a cluster of receiving-only satellites flying in a close formation, in the framework of the array theory. Indeed, the imaging properties of different close receivers, when analyzed as isolated items, are very similar and form the so-called common array. Moreover, the relative positions among the receivers implicitly define a physical array, referred to as spatial diversity array. FF-SAR imaging can be verified as a result of the spatial diversity array weighting the common array. Hence, different approaches to beamforming can be applied to the spatial diversity array to provide the FF-SAR with distinctive capabilities, such as coherent resolution enhancement and high-resolution wide-swath imaging. Simulation examples are discussed which confirm that array theory is a powerful tool to quickly and easily characterize FF-SAR imaging performance.
Highlights
Spaceborne synthetic aperture radar (SAR) remote sensing missions have been delivering operational products and services since the early 1990s
Bistatic, and multistatic SAR can be recast into a single theoretical framework by the array theory
For a multistatic SAR the effect of the physical separation among the receivers is described by the spatial diversity array
Summary
Spaceborne synthetic aperture radar (SAR) remote sensing missions have been delivering operational products and services since the early 1990s. The present work is mainly focused on FF-SAR imaging features, that is on the derivation of an analytical model to be used for evaluation of FF-SAR imaging performance This FF-SAR image, thanks to the spatial diversity of the collection geometry and the redundancy of the measurements, is characterized by enhanced properties with respect to the image that a single receiver of the formation can generate when operating as an isolated item. The introduced approach is of quite general validity meaning that it can be applied to 1) close satellite formations including both a monostatic SAR and a given number of receivers, as in [3] and [27]; 2) companion satellite-like configurations, i.e., large satellite formations with a transmitter that is relatively far from a cluster of receivers, as in [29]–[33]; 3) formations of close receivers working with transmitters operating at completely different ranges of altitude and velocity, as in [34]–[37].
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