Precise Orbit and Baseline Determination for the SAOCOM-CS Bistatic Radar Mission

Clutter cancellation and long time integration are two vital steps for global navigation satellite system (GNSS)-based bistatic radar target detection. The former eliminates the influence of direct and multipath signals on the target detection performance, and the latter improves the radar detection range. In this paper, the extensive cancellation algorithm (ECA), which projects the surveillance channel signal in the subspace orthogonal to the clutter subspace, is first applied in GNSS-based bistatic radar. As a result, the clutter has been removed from the surveillance channel effectively. For long time integration, a modified version of the Fourier transform (FT), called long-time integration Fourier transform (LIFT), is proposed to obtain a high coherent processing gain. Relative acceleration (RA) is defined to describe the Doppler variation results from the motion of the target and long integration time. With the estimated RA, the Doppler frequency shift compensation is carried out in the LIFT. This method achieves a better and robust detection performance when comparing with the traditional coherent integration method. The simulation results demonstrate the effectiveness and advantages of the proposed processing method.

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Processing-Based Synchronization Approach for Bistatic Radar Glacial Tomography

IGARSS 2020 - 2020 IEEE International Geoscience and Remote Sensing Symposium ◽

10.1109/igarss39084.2020.9323969 ◽

2020 ◽

Author(s):

Nicole L. Bienert ◽

Dustin M. Schroeder ◽

Sean T. Peters ◽

Matthew R. Siegfried

Keyword(s):

Bistatic Radar

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General relativistic effects acting on the orbits of Galileo satellites

Celestial Mechanics and Dynamical Astronomy ◽

10.1007/s10569-021-10014-y ◽

2021 ◽

Vol 133 (4) ◽

Author(s):

K. Sośnica ◽

G. Bury ◽

R. Zajdel ◽

K. Kazmierski ◽

J. Ventura-Traveset ◽

...

Keyword(s):

General Relativity ◽

Orbit Determination ◽

Final Height ◽

Precise Orbit Determination ◽

Satellite System ◽

De Sitter ◽

Circular Orbits ◽

Precise Orbit ◽

Artificial Earth Satellites ◽

Artificial Earth

AbstractThe first pair of satellites belonging to the European Global Navigation Satellite System (GNSS)—Galileo—has been accidentally launched into highly eccentric, instead of circular, orbits. The final height of these two satellites varies between 17,180 and 26,020 km, making these satellites very suitable for the verification of the effects emerging from general relativity. We employ the post-Newtonian parameterization (PPN) for describing the perturbations acting on Keplerian orbit parameters of artificial Earth satellites caused by the Schwarzschild, Lense–Thirring, and de Sitter general relativity effects. The values emerging from PPN numerical simulations are compared with the approximations based on the Gaussian perturbations for the temporal variations of the Keplerian elements of Galileo satellites in nominal, near-circular orbits, as well as in the highly elliptical orbits. We discuss what kinds of perturbations are detectable using the current accuracy of precise orbit determination of artificial Earth satellites, including the expected secular and periodic variations, as well as the constant offsets of Keplerian parameters. We found that not only secular but also periodic variations of orbit parameters caused by general relativity effects exceed the value of 1 cm within 24 h; thus, they should be fully detectable using the current GNSS precise orbit determination methods. Many of the 1-PPN effects are detectable using the Galileo satellite system, but the Lense–Thirring effect is not.

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A Second-Order Time-Difference Position Constrained Reduced-Dynamic Technique for the Precise Orbit Determination of LEOs Using GPS

Remote Sensing ◽

10.3390/rs13153033 ◽

2021 ◽

Vol 13 (15) ◽

pp. 3033

Author(s):

Hui Wei ◽

Jiancheng Li ◽

Xinyu Xu ◽

Shoujian Zhang ◽

Kaifa Kuang

Keyword(s):

Orbit Determination ◽

Dynamic Models ◽

Precise Orbit Determination ◽

Second Order ◽

Time Difference ◽

Error Sources ◽

Precise Orbit ◽

Unmodeled Dynamic ◽

Reduced Dynamic

In this paper, we propose a new reduced-dynamic (RD) method by introducing the second-order time-difference position (STP) as additional pseudo-observations (named the RD_STP method) for the precise orbit determination (POD) of low Earth orbiters (LEOs) from GPS observations. Theoretical and numerical analyses show that the accuracies of integrating the STPs of LEOs at 30 s intervals are better than 0.01 m when the forces (<10−5 ms−2) acting on the LEOs are ignored. Therefore, only using the Earth’s gravity model is good enough for the proposed RD_STP method. All unmodeled dynamic models (e.g., luni-solar gravitation, tide forces) are treated as the error sources of the STP pseudo-observation. In addition, there are no pseudo-stochastic orbit parameters to be estimated in the RD_STP method. Finally, we use the RD_STP method to process 15 days of GPS data from the GOCE mission. The results show that the accuracy of the RD_STP solution is more accurate and smoother than the kinematic solution in nearly polar and equatorial regions, and consistent with the RD solution. The 3D RMS of the differences between the RD_STP and RD solutions is 1.93 cm for 1 s sampling. This indicates that the proposed method has a performance comparable to the RD method, and could be an alternative for the POD of LEOs.

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