Abstract
Temporal decorrelation is a critical parameter for repeat-pass coherent radar processing, including many advanced techniques such as polarimetric SAR interferometry (PolInSAR) and SAR tomography (TomoSAR). Given the multifactorial and unpredictable causes of temporal decorrelation, statistical analysis of long time series of measurements from tower-based scatterometers is the most appropriate method for characterizing how rapidly a specific scene decorrelates. Based on the TropiScat experiment that occurred in a tropical dense forest in French Guiana, this letter proposes a comparative analysis between temporal decorrelation at P-band and at higher frequencies in the range of 800–1000 MHz (the low end of the L-band). This letter aims to support the design of future repeat-pass spaceborne missions and to offer a better understanding of the physics behind temporal decorrelation. Beyond the expected lower values that are found and quantified at the low L-band compared with the P-band, similar decorrelation patterns related to rainy and dry periods are emphasized in addition to the critical impacts of acquisition time during the day.
Highlights
A S A CONSEQUENCE of the temporal variations that impact radar coherent backscattering, temporal decorrelation is typically characterized by the loss of coherence between repeat pass acquisitions
Fostered by the preparation phase of the Biomass mission [2], [3], the extensive time series of measurements that can be sourced from tower-based experiments such as the TropiScat, the current AfriScat [10], or the in-development BorealScat [11] are highly relevant for this purpose, considering the added value of simultaneous measurements from the scatterometer and those related to the flux tower
These experiments are limited by their footprint extent over a specific location such that the scope of the current analysis based on the TropiScat experiment, which occurred near the Paracou research station (French Guiana), is restricted to tropical forests for which short-term temporal changes are primarily driven by diurnal variations and longterm changes are driven by conditions during dry and rainy seasons
Summary
A S A CONSEQUENCE of the temporal variations that impact radar coherent backscattering, temporal decorrelation is typically characterized by the loss of coherence between repeat pass acquisitions. TropiSAR airborne repeat-pass acquisitions have shown that TomoSAR and PolInSAR processing can accommodate temporal coherences of approximately 0.8 without correction, whereas the TropiScat results showed that such a level can be ensured with a temporal baseline shorter than three days at the P-band Bearing in mind these key figures for the design of TomoSAR or PolInSAR spaceborne missions, this letter proposes extension and comparison of the previous analysis based on the TropiScat results at the P-band with higher frequencies for an improved understanding of temporal decorrelation and investigation of future scenarios of L-band spaceborne missions operating near 1.2 GHz [21]. Further prospects of applications are discussed in the conclusion
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