This training manual introduces and explains Interferometric Synthetic Aperture Radar (InSAR), including applications for data from the Envisat ASAR sensor and how to combine Envisat and ERS images to produce interferograms and differential interferograms.
Synthetic Aperture Radar (SAR) is a microwave imaging system. It has cloud penetrating capabilities because it uses microwaves; it has day and night operational capabilities because it is an active system; and its ‘interferometric configuration’, Interferometric SAR or InSAR, allows accurate measurements of the radiation travel path because it is coherent. Measurements of travel path variations as a function of the satellite position and time of acquisition allow generation of digital elevation models and measurement of centimetric surface deformations of the terrain.
In 1991, ESA launched the first European Remote Sensing satellite, ERS 1, and started building a catalogue of interferometric data covering the whole Earth. ERS 2 was launched in 1995, to continue and expand the work. For nine months in 1995/1996, the two satellites undertook a ‘tandem’ mission, in which they orbited Earth only 24 hours apart. The image pairs acquired provide much greater interferogram coherence than is normally possible, allowing scientists to generate detailed digital elevation maps and observe changes over a very short space of time.
In March 2000, ERS-1 ended operations. ERS-2 continues to operate, and in 2002 was joined by Envisat, the largest Earth observation satellite ever built. Envisat and ERS-2 images are compatible for interferometry processing purposes and the satellites continue to work together, adding to the ever growing set of interferometric data.
ESA TM-19 has been produced as a text book to introduce radar interferometry to remote sensing specialists. It consists of three parts:
Part A is for readers with a good knowledge of optical and microwave remote sensing, to acquaint them with interferometric SAR image processing and interpretation.
Part B provides a practical approach and the technical background for beginners with InSAR processing.
Part C contains a more mathematical approach, for a deeper understanding of the interferometric process. It includes themes such as super resolution and ERS/Envisat interferometry.
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