Synthetic Aperture Radar
This three-day class will first set the historical context of SAR by tracing the rapid development of radar technology from the early part of the twentieth century through the 1950s when the Synthetic Aperture Radar techniques were first developed and demonstrated. A technical description of the important mathematical relationships to radar and SAR will be presented. The student will learn what radar cross-section is and how it applies to traditional radar and SAR. Fundamental equations governing SAR performance such as the radar range equation, SAR resolution equations, and SAR signal-to-noise equations will be developed and presented. We will design a simple SAR system in class and derive its predicted performance and sensitivities. A complete description of SAR phenomenology will be provided so that the student will better be able to interpret SAR imagery. Connections between SAR’s unique image characteristics and information extraction will be presented. Perhaps the most important and interesting material will be presented in the advanced SAR sections. Here topics such as SAR polarimetry and interferometry will be presented, along with the latest applications of these technologies. Many examples will be presented.
What you will learn:
- Invention and early development of radar and SAR
- How a SAR collects data & how it is processed
- The “beautiful equations” describing SAR resolution
- What is radar cross-section? What is a SAR’s “noise equivalent sigma zero?” How do you calculate this?
- Design-a-SAR: Interactive tool that shows predicted SAR performance based on SAR parameters
- SAR Polarimetry and applications
- SAR Interferometry and applications, including differential SAR and terrain mapping.
- Introduction. Background and motivation (both scientific and political) for the rapid development of radar and SAR technology
- Fundamentals of Radar. The radar range equation, calculation and meaning of radar cross-section, target detection, waveform coding, thermal noise and other noise sources, RF/radar antennas and how they work, radar system block diagram
- Synthetic Aperture Radar Fundamentals. Description how a SAR works, synthetic aperture imaging, the difference between synthetic and real-aperture imaging, example SAR systems and performances. Various SAR modes will be described including stripmap, spotlight and various scan modes. Example SAR systems that employ these modes will be described.
- SAR Phenomenology. SAR image interpretation, SAR layover, shadows, multi-path, types of SAR scattering: surface scattering, forward scattering, volume scattering, frequency dependency of RCS and other frequency dependent effects, SAR speckle, noise and noise sources, ambiguities (range and azimuth), visualization of SAR data.
- SAR Systems. An overview of various SAR systems and illustrative imagery examples from those systems is presented. Both airborne and spaceborne systems are described along with their performance.
- SAR Image Exploitation & Applications. Ways to extract information from SAR data. This section focuses on what kind of information can be derived from a single SAR image. Unique capabilities are highlighted as are various deficiencies. Further examples of exploitation using two and multiple images are described within the later sections.
- Design-a-SAR. An interactive software tool will be used by the class to design a SAR system by setting SAR parameters such as desired resolution, power, acquisition geometry (including height and range), frequency, bandwidth, sampling rates, antenna size/gain, etc. Tool will enforce consistent SAR design constraints presented in class. Sensitivity of the resulting SAR data is calculated. This exercise clearly demonstrates the challenges and trade-offs involved when designing a SAR system for a particular mission.
- SAR Polarimetry. Description of what polarimetry is in general, and how it can be used in the case of SAR. Examples of polarimetric SAR systems are described and example applications are presented. Single-polarization, dual-polarization and quad-polarization SAR is addressed. Compact polarization is also discussed in the context of SAR.
- Coherent SAR Applications: Two images. SAR change detection, both coherent and incoherent. SAR interferometry for elevation mapping, SAR interferometry for measuring ground motion (differential interferometric SAR). Along-track interferometry for ocean applications and GMTI. Case study examples.
- Coherent SAR Applications: Greater than two images. Sparse aperture processing for extraction of elevation data including 3D SAR point clouds, Coherent processing of stacks of data for estimation of scatterer motion over time, permanent scatterer (PS) interferometric techniques. Case study examples.
- SAR Future. A description of upcoming SAR missions and systems and their capabilities. Description of key technologies and new approaches for data acquisition and processing.
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Mr. Richard Carande. From 1986 to 1995 Mr. Carande was a group leader for a SAR processor development group at the Jet Propulsion Laboratory (Pasadena California). There he was involved in developing an operational SAR processor for the JPL/NASA’s three-frequency, fully polarimetric AIRSAR system. Mr. Carande also worked as a System Engineer for the Alaska SAR Processor while at JPL, and performed research in the area of SAR Along-Track Interferometry. Before starting at JPL, Mr. Carande was employed by a technology company in California where he developed optical and digital SAR processors for internal research applications. Mr. Carande has a BS & MS in Physics from Case Western Reserve University.
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