Effects of the spatio-temporally varying atmosphere on sar imaging: the ionosphere case - expro plus

To derive more accurate expression of atmosphere irregularities effects with a focus on the ionosphere, and devise mitigation techniques for both geo- and sun-synchronous SAR imaging systemsDescription: For Low Earth Orbit (LEO) Synthetic Aperture Radar (SAR) systems the atmospheric turbulence is generally assumed to be time-invariant during the synthetic aperture time due to itsshort duration. Such assumption is not always correct, as horizontal atmospheric drifts and vortices exist. Especially for SAR systems at low frequency (P-Band, L-Band), SAR operating on repeat-track basis, geo-synchronous SAR systems characterised by long integration time and extensive imaging scene, the ionosphere can have an important role on the performance. Furthermore, both temporal andspatial variations of the ionosphere have to be jointly taken into account, which further complicates their characterisation. Therefore, the effects of the flowing ionospheric irregularities need to be investigated, aiming in particular to image shifts, defocusing and repeat-track interferometry. The aim of this activity is to provide a comprehensive analysis to evaluate effects of both spatial variation and flowing ionospheric irregularities on SAR systems operating both at P-, L- and C-band. In particular, the ionospheric scintillations, which act remarkably in the polar cap and equatorial zone at night need to be considered. The Ionosphere characterisation shall originate from previous developments, analyses performed in the framework of previous missions developments and from knowledge built up in the navigation community. This activity encompasses the following tasks: -Analytical models of the physical effects of spatial-temporally ionospheric background variations on the SAR signal. - Assessment of the impacts on the SAR performancesdemonstrating, both theoretically and numerically, the geometric fidelity, focusing aspect and interferometry quality (i.e., relative image shifts and the decorrelation of interferometric pairs, interferometric phase screen errors). - Validation of the models andof the performance analysis using ionospheric monitoring measurements (i.e., Global Positioning System). - Develop mitigation techniques. - The implementation of the aforementioned components in a software framework. The methods developed in this activity are expected to be developed in such a way that they can be later broadened to other atmospheric effects such as tropospheric scintillations. Software shall be delivered under an ESA Software Community License, so that any individuals or entities within ESA Member Statescan access to it and can provide update to the community of users.Deliverables: Report, SoftwareProcurement Policy: C(3) = Activity restricted to SMEs RD Entities. For additional information please go to:http://www.esa.int/About_Us/Business_with_ESA/Small_and_Medium_Sized_Enterprises/Opportunities_for_SMEs/Procurement_policy_on_fair_access_for_SMEs_-_the_C1-C4_Clauses.