1. Temporal decorrelation effects from scatterer motion can severely degrade the performance of SAR tomography by causing loss of elevation resolution and accuracy. 2. Model-based SAR tomography is more strongly affected by temporal decorrelation compared to adaptive beamforming tomography. Acquisition time spans greater than half the decorrelation time can critically impact performance. 3. Differential tomography is proposed as a new approach that accounts for temporal changes and can extract elevation information more robustly even in temporally decorrelating scenes. It shows potential to improve SAR tomography for future spaceborne missions.

1. Temporal decorrelation effects in super-resolution 3D Tomosar Francesco Cai, Fabrizio Lombardini, Lucio Verrazzani University of Pisa Department of Information Engineering Gold conference 2010 Livorno, April 29 2009

9. SAR Tomography criticalities Which temporal decorrelation condition is critical for SAR tomography functionality? Resolution(%), multistatic configuration Useful indications in the planning of future missions such as ESA-BIOMASS and DLR TanDEM-L. Acquisition time >≈ ½-⅓ τ c Acquisition time >≈ τ c Criticalities for model-based SAR Tomograpy : strong loss for resolution probability Adaptive BF method is more robust to temporal decorrelation effects than model –based method Acquisition time ≈ ⅓ τ c Adaptive BF Tomo SAR begins to perform better than model-based

10. A new approach: the Differential SAR Tomography framework Point-like scatterer in height Uniform motion (l.o.s. direction) spatial harmonic temporal harmonic Discrete space-time spectrum Temporal frequencies code velocities Example: subsidence in urban layover areas Extended scatterers in height Range of velocities spatial harmonic distribution temporal harmonic distribution Continuous space-time spectrum Temporal frequencies code velocities Example: a glacier flow (sliding random volume over ground) Temporal decorrelation of a scattering component temporal harmonic distribution Temporal frequencies are signatures of the temporal decorrelation ! [Lombardini-Fornaro, IGARSS’05] [Fornaro-Serafino-Reale, IEEE-TGARS’09] [Lombardini, ESA FRINGE Wrkshp’07] Diff-Tomo exploits the multibaseline-multitemporal information content to enter the SAR pixel and extract separated information on elevation and velocity of multiple superimposed scatterers [Lombardini, TGARS Jan. 2005] “ Diff-Tomo” is a new interferometric mode, which avoids the misinterpretation of spatial signal histories (scatterers location) and temporal histories in non-stationary scenarios Temporal signal histories from decorrelation can be decoupled from the spatial spectral estimation . D-InSAR and Tomo-SAR crossed in an unified framework Joint elevation-velocity resolution of multiple scatterers