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Remote Sens. 2017, 9(9), 933; doi:10.3390/rs9090933

Performance Analysis of Ocean Surface Topography Altimetry by Ku-Band Near-Nadir Interferometric SAR

1,2,* and 4,5,*
National Key Laboratory of Science and Technology on Microwave Imaging, Beijing 100190, China
Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China
School of Electronics, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100190, China
Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences, Beijing 100094, China
Key Laboratory of Space Utilization, Chinese Academy of Sciences, Beijing 100094, China
Authors to whom correspondence should be addressed.
Received: 14 August 2017 / Revised: 4 September 2017 / Accepted: 6 September 2017 / Published: 9 September 2017
(This article belongs to the Special Issue Ocean Remote Sensing with Synthetic Aperture Radar)
View Full-Text   |   Download PDF [5437 KB, uploaded 9 September 2017]   |  


Interferometric imaging radar altimeter (InIRA) is the first spaceborne Ku-band interferometric synthetic aperture radar (InSAR) which is specially designed for ocean surface topography altimetry. It is on the Tiangong II space laboratory, which was launched on 15 September 2016. Different from any other spaceborne synthetic aperture radar (SAR), InIRA chooses a near-nadir incidence of 1°~8° in order to increase the altimetric precision and swath width. Limited by the size of the Tiangong II capsule, the baseline length of InIRA is only 2.3 m. However, benefitting from the low orbit, the signal-to-noise ratio of InIRA-acquired data is above 10 dB in most of the swath, which, to a certain extent, compensates for the short baseline deficiency. The altimetric precision is simulated based on the system parameters of InIRA. Results show that it is better than 7 cm on a 5-km grid and improves to 3 cm on a 10-km grid when the incidence is below 7.4°. The interferometric data of InIRA are processed to estimate the altimetric precision after a series of procedures (including image coregistration, flat-earth-phase removal, system parameters calibration and phase noise suppression). Results show that the estimated altimetric precision is close to but lower than the simulated precision among most of the swath. The intensity boundary phenomenon is first found between the near range and far range of the SAR images of InIRA. It can be explained by the modulation of ocean internal waves or oil slick, which smooths ocean surface roughness and causes the modulated area to appear either brighter or darker than its surroundings. This intensity boundary phenomenon indicates that the available swath of high altimetric precision will be narrower than expected. View Full-Text
Keywords: InSAR; near-nadir incidence; Ku-band; ocean surface topography; altimetry InSAR; near-nadir incidence; Ku-band; ocean surface topography; altimetry

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Kong, W.; Chong, J.; Tan, H. Performance Analysis of Ocean Surface Topography Altimetry by Ku-Band Near-Nadir Interferometric SAR. Remote Sens. 2017, 9, 933.

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