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Synthetic Aperture Radiometer

Synthetic Aperture Radiometer. James Tianchen Li EECS 823, Spring 2013. Synthetic Aperture vs. Real Aperture. Real apertures become impractically large as the spatial resolution requirements from space at microwave frequencies increase .

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Synthetic Aperture Radiometer

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  1. Synthetic Aperture Radiometer James Tianchen Li EECS 823, Spring 2013

  2. Synthetic Aperture vs. Real Aperture • Real apertures become impractically large as the spatial resolution requirements from space at microwave frequencies increase. • Aperture synthesis can use pairs of small antennas and signal processing to obtain the resolution of a single large antenna.

  3. Interferometric Imaging • Interferometricaperture synthesis is presented as an alternative to real aperture measurements of the earth’s brightness temperature from low earth orbitImagesynthesis techniques developed for radio astronomy that utilize the interference pattern formed by cross-correlating a pair of spatially separated antenna elements offer an attractive alternative to the real aperture. [1]

  4. Interferometric Imaging Fundamentals [1]

  5. Quadrature (complex) antenna correlator – Receiver noise is added at the antenna terminals. The signals are bandpass filtered prior to quadrature correlation. The finite duration time integration is represented as a lowpass filter. The output real and imaginary components of the visiblility function are corrupted by statistically dependent additive noise with standard deviations ΔVrand ΔVi, respectively.

  6. Block diagram of the sideband correlator

  7. The Electronically Steered Thinned Array Radiometer (ESTAR) is a hybrid which uses real aperture for along-track resolution and aperture synthesis for cross-track resolution.

  8. Block diagram of the ESTAR instrument

  9. The ESTAR prototype one-dimensional imaging interferometer All five antenna elements have coincident fan beam antenna patterns over a strip of the earth. The simultaneous cross-correlation of all pairs of antenna elements produces a Nyquist sampled estimate of the visiblility function V(n(λ/2); n = 0,1,…,8), which is the Fourier transform of the brightness temperature distribution Tφ (φ)

  10. An artist's concept of the SMOS satellite with deployed solar arrays and instrument • SMOS concept (Soil Moisture and Ocean Salinity)Aperture synthesis in two dimensions

  11. Reference • [1] Ruf, C. S.; Swift, C. T., et al., "Interferometric Synthetic Aperture Microwave Radiometry for the Remote Sensing of the Earth", IEEE Trans. GRS, vol. 26, no.5, 1, pp. 597-611, 1988 • [2] D. M. Le Vine, "ESTAR: A synthetic aperture microwave radiometer for remote sensing applications", Proceeding of IEEE IGARSS conference, pp. 1787-99, 1994 • [3] Le Vine, D.M. "Synthetic aperture radiometer systems",  Microwave Theory and Techniques, IEEE Transactions on, On page(s): 2228 - 2236 Volume: 47, Issue: 12, Dec 1999

  12. Thank You

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