A Semianalytical Model of the Synthetic Aperture, Interferometric Radar Altimeter Mean Echo, and Echo Cross-Product and Its Statistical Fluctuations

• Published in: IEEE transactions on geoscience and remote sensing 2018-05, Vol.56 (5), p.2539-2553
• Main Authors: Wingham, Duncan J., Giles, Katharine A., Galin, Natalia, Cullen, Robert, Armitage, Thomas W. K., Smith, Walter H. F.
• Format: Article
• Language: English
• Subjects: Altimeters; Altimetry; Antenna measurements; Apertures; Beamforming; Data processing; Dimensions; Echoes; Fluctuations; Fossils; Geophysical sea measurements; Interferometry; Mathematical models; ocean surface; Oceans; Pitch (inclination); Radar; Radar altimeters; Radar altimetry; radar remote sensing; Radio altimeters; Rolling motion; SAR (radar); Satellites; Sea measurements; Spaceborne radar; Synthetic aperture radar; synthetic aperture radar (SAR); Temperature (air-sea)
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2017.2756854

This paper develops a model of the synthetic aperture, interferometric satellite radar altimeter echo power, and echo cross-product. The model uses the smallness of the satellite pitch and roll angles, and the limited range of satellite altitude to provide a semianalytical echo model, whose numerical dimensions are limited to two in the synthetic aperture case or three in the interferometric case at large roll angles, making its application to extensive data practical. By not implementing the synthetic beam formation, it is demonstrated that the model recovers the conventional case of a pulse-limited altimeter. A theoretical description of the fluctuations in the multilooked, interferometric cross-product, and the synthetic aperture and pulse-limited powers is given by extending the model to describe correlations between individual looks in each case. The model offers the potential to retrieve ocean-surface parameters from synthetic aperture and pulse-limited altimeter data simultaneously, with obvious application to the new generation of altimeters onboard CryoSat-2, Sentinel-3, and Sentinel-6 during the transition to operational synthetic aperture radar altimetry.