Effect of orbital errors on the geosynchronous circular synthetic aperture radar imaging and interferometric processing

Kou, Leilei; Wang, Xiaoqing; Xiang, Maosheng; Chong, Jong‐Wha; Zhu, Meiping

doi:10.1631/jzus.c1000170

Cited by 16 publications

(13 citation statements)

References 20 publications

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“…5000 < h ≤ 10, 000 28.8 − 0.00556 h − 10 4 10 4 < h < 1.5 × 10 4 (34) where t 0 is the ground temperature and u 0 is the ground refractive rate.…”

Section: T+24097mentioning

confidence: 99%

Modeling and Quantitative Analysis of Tropospheric Impact on Inclined Geosynchronous SAR Imaging

Dong

et al. 2019

Remote Sensing

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Geosynchronous orbit synthetic aperture radar (GEO SAR) has a long integration time and a large imaging scene. Therefore, various nonideal factors are easily accumulated, introducing phase errors and degrading the imaging quality. Within the long integration time, tropospheric status changes with time and space, which will result in image shifts and defocusing. According to the characteristics of GEO SAR, the modeling, and quantitative analysis of background troposphere and turbulence are conducted. For background troposphere, the accurate GEO SAR signal spectrum, which takes into account the time-varying troposphere, is deduced. The influences of different rates of changing (ROC) of troposphere with time are analyzed. Finally, results are verified using the refractive index profile data from Fengyun (FY) 3C satellite and the tropospheric zenith delays data from international GNSS service (IGS). The time–space changes of troposphere can cause image shifts which only depend on the satellite beam-foot velocity and the linear ROC of troposphere. The image defocusing is related to the wavelength, resolution requirement, and the second and higher orders of ROC. The short-wavelength GEO SAR systems are more susceptible to impacts, while L-band GEO SAR will be affected when the integration time becomes longer. Tropospheric turbulence will cause the amplitude and phase random fluctuations resulting in image defocusing. However, in the natural environment, radio waves are very weakly affected by turbulence, and the medium-inclined GEO SAR of L- to C-band will not be affected, while the X-band will be influenced slightly.

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“…5000 < h ≤ 10, 000 28.8 − 0.00556 h − 10 4 10 4 < h < 1.5 × 10 4 (34) where t 0 is the ground temperature and u 0 is the ground refractive rate.…”

Section: T+24097mentioning

confidence: 99%

Modeling and Quantitative Analysis of Tropospheric Impact on Inclined Geosynchronous SAR Imaging

Dong

et al. 2019

Remote Sensing

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“…With the linear variation in TEC during the synthetic aperture length, the equivalent variation along the circular aperture is approximately a sine function acos(θ + b). From [6], we know that the range error (in the form of sine function) due to the ionospheric horizontal gradient will cause the image shift on the XY plane, and the image shift in the x-and y-direction will be…”

Section: Ionospheric Effects On Geocsar Imagingmentioning

confidence: 99%

“…With appropriate geosynchronous orbital parameters, the geosynchronous synthetic aperture shapes can be circular, elliptical and 'figure of 8'. Thus, circular SAR (CSAR) can be extended to the geosynchronous orbit utilising the motion of a satellite in an orbit modelled as a circular trajectory, and the geosynchronous CSAR (GEOCSAR) is possible [4][5][6]. The CSAR imaging on the geosynchronous orbit has significant potential advantages over the conventional low-Earth orbit (LEO) SAR, such as large coverage, short repeat period, high-resolution three-dimensional (3D) imaging and continuous surveillance of an interested area [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Ionospheric effects on three‐dimensional imaging of L‐band geosynchronous circular synthetic aperture radar

Kou

Xiang

Wang

2014

IET Radar, Sonar & Navigation

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Circular synthetic aperture radar (SAR) imaging on the geosynchronous orbit has many potential advantages, such as high-resolution three-dimensional (3D) imaging and continuous surveillance of broad area. The mission considered is an L-band geosynchronous circular SAR (GEOCSAR) with full aperture measurement. Since the integration time of GEOCSAR can be as long as 24 h, the orbit altitude is about 36 000 km and the coverage may reach 1/3 of the Earth's surface. The spatial and temporal variation of the ionosphere may impose significant effects on 3D imaging performance of GEOCSAR. The effects of ionospheric spatial variation including vertical and horizontal structure, the ionospheric turbulence and the ionospheric temporal variation are discussed. The analysis shows that the temporal variation of the ionospheric electron content during the synthetic aperture and the ionospheric turbulence may severely affect the GEOCSAR focusing performance on the XY plane. The vertical and horizontal structure of the ionosphere will cause image shift, and the dispersion effect is negligible.

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“…The perturbed orbit drifts among days or weeks can form the spatial baseline between the repeat pass GEO SAR and can be employed for the repeat pass interferometry or the differential interferometry [ 15 , 16 ]. In comparison, the perturbed orbit variations within one day or the GEO SAR aperture time (several hundreds or even thousands of seconds) can lead to the changing of the slant range histories and result in the degradation and even the failure of focusing [ 17 , 18 ].…”

Section: Introductionmentioning

confidence: 99%

“…Kou et al [ 17 ] studies the perturbed orbit variations’ effects on the focusing and interferometry of the circular SAR (CSAR). However, the CSAR is an innovative SAR system, which has a circular nadir track and forms high resolution images by the coherent integration of the whole day’s (the orbit period) acquisitions.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of Orbital Perturbation Effects on Inclined Geosynchronous SAR

Dong

et al. 2016

Sensors

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The geosynchronous synthetic aperture radar (GEO SAR) is susceptible to orbit perturbations, leading to orbit drifts and variations. The influences behave very differently from those in low Earth orbit (LEO) SAR. In this paper, the impacts of perturbations on GEO SAR orbital elements are modelled based on the perturbed dynamic equations, and then, the focusing is analyzed theoretically and numerically by using the Systems Tool Kit (STK) software. The accurate GEO SAR slant range histories can be calculated according to the perturbed orbit positions in STK. The perturbed slant range errors are mainly the first and second derivatives, leading to image drifts and defocusing. Simulations of the point target imaging are performed to validate the aforementioned analysis. In the GEO SAR with an inclination of 53° and an argument of perigee of 90°, the Doppler parameters and the integration time are different and dependent on the geometry configurations. Thus, the influences are varying at different orbit positions: at the equator, the first-order phase errors should be mainly considered; at the perigee and apogee, the second-order phase errors should be mainly considered; at other positions, first-order and second-order exist simultaneously.

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Effect of orbital errors on the geosynchronous circular synthetic aperture radar imaging and interferometric processing

Cited by 16 publications

References 20 publications

Modeling and Quantitative Analysis of Tropospheric Impact on Inclined Geosynchronous SAR Imaging

Modeling and Quantitative Analysis of Tropospheric Impact on Inclined Geosynchronous SAR Imaging

Ionospheric effects on three‐dimensional imaging of L‐band geosynchronous circular synthetic aperture radar

Numerical Analysis of Orbital Perturbation Effects on Inclined Geosynchronous SAR

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