Numerical Analysis of Orbital Perturbation Effects on Inclined Geosynchronous SAR

Abstract

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.

Study on Optimal Broadcast Ephemeris Parameters for GEO/IGSO Navigation Satellites

“…The IGSO/GEO satellites are predominately influenced by spherical harmonics, attraction of third bodies (Sun and Moon), and solar radiation pressure in addition to central gravity [ 19 ]. Keplerian orbital elements ( ), which denote semimajor axis, eccentricity, inclination, right ascension of the ascending node (RAAN), argument of perigee, and mean anomaly, can typically express satellite motion around the Earth.…”

“…Specifically, the short-term variations of ( ) were caused by the zonal terms of the Earth’s gravitational force and luni-solar attractions, and the short-term variations of ( ) were caused by solar radiation pressure. The detailed analysis on the periodic motion of orbital elements can be found in the literature [ 19 , 21 , 22 ]. These analyses allowed us to design a user algorithm for reconstructing the broadcast ephemeris by taking into account the dominant frequency and characteristics of orbital elements for IGSO/GEO satellites.…”

A Generalized Chirp-Scaling Algorithm for Geosynchronous Orbit SAR Staring Observations

“…In the slant range, because of the ultra-long integration time, the effect of perturbing orbital elements on the satellite and target kinematic parameters should be taken into account [ 29 ]. As indicated in [ 31 ], the satellite and target kinematic parameters that can be obtained from the orbital elements include the following: , i.e., the semimajor axis of the orbit, , i.e., the eccentricity of the orbit, , i.e., the inclination of the orbit, and Ω , i.e., the longitude of the ascending node, , i.e., the true anomaly, , i.e., the argument of perigee.…”

“…Ruiz et al [ 28 ] proposed the method of retrieving the atmospheric phase screen (APS) and compensating its effects on GEO SAR focusing. To improve GEO SAR focusing influenced by perturbations, Dong et al [ 29 ] recommended the use of accurate orbit measurements or some signal processing methods. The autofocus technique for phase error correction has been proven to be a robust technique that can compensate for the phase error caused by atmosphere or orbit perturbations [ 30 ].…”

Computerized ionospheric tomography based on geosynchronous SAR

“…Since it was first proposed by Tomiyasu [], GEO SAR has attracted more and more attention. Especially in recent years, great research progresses have been made, most of which are mainly concentrated on the imaging technique [ Hu et al ., , , ; Ding et al ., ], system parameter analysis and design [ Hobbs et al ., ; Dong et al ., ; Ruiz‐Rodon et al ., ; Guarnieri et al ., ], atmosphere effects [ Recchia et al ., ; Hu et al ., ; Tian et al ., ; Dong et al ., ], and so on.…”