@article{fdi:010088857,
  title = {{I}onospheric compensation in {L}-band {I}n{SAR} time-series : performance evaluation for slow deformation contexts in equatorial regions},
  author = {{M}arconato, {L}. and {D}oin, {M}. {P}. and {A}udin, {L}aurence and {P}athier, {E}.},
  editor = {},
  language = {{ENG}},
  abstract = {{M}ulti-temporal {S}ynthetic {A}perture {R}adar {I}nterferometry ({MT}-{I}n{SAR}) is the only geodetic technique allowing to measure ground deformation down to mm/yr over continuous areas. {V}egetation cover in equatorial regions favors the use of {L}-band {SAR} data to improve interferometric coherence. {H}owever, the electron content of ionosphere, affecting the propagation of the {SAR} signal, shows particularly strong spatio-temporal variations near the equator, while the dispersive nature of the ionosphere makes its effect stronger on low-frequencies, such as {L}-band signals. {T}o tackle this problem, range split-spectrum method can be implemented to compensate the ionospheric phase contribution. {H}ere, we apply this technique for time-series of {ALOS}-{PALSAR} data, and propose optimizations for low-coherence areas. {T}o evaluate the efficiency of this method to retrieve subtle deformation rates in equatorial regions, we compute time-series using four {ALOS}-{PALSAR} datasets in contexts of low to medium coherence, showing slow deformation rates (mm/yr to cm/yr). {T}he processed tracks are located in {E}cuador, {T}rinidad and {S}umatra, and feature 15 to 19 acquisitions including very high, dominating ionospheric noise, corresponding to equivalent displacements of up to 2 m. {T}he correction method performs well and allows to reduce drastically the noise level due to ionosphere, with significant improvement compared with a simple plane fitting method. {T}his is due to frequent highly non-linear patterns of perturbation, characterizing equatorial {TEC} distribution. {W}e use semivariograms to quantify the uncertainty of the corrected time-series, highlighting its dependence on spatial distance. {T}hus, using {ALOS}-{PALSAR}-like archive, one can expect a detection threshold on the {L}ine-of-{S}ight velocity ranging between 3 and 6 mm/yr, depending on the spatial wavelength of the signal to be observed. {T}hese values are consistent with the accuracy derived from the comparison of velocities between two tracks in their overlapping area. {I}n the case studies that we processed, the time-series corrected from ionosphere allows to retrieve accurately fault creep and volcanic signal but it is still too noisy for retrieving tiny long-wavelength signals such as slow (mm/yr) interseismic strain accumulation.},
  keywords = {{S}ynthetic aperture radar {SAR} interferometry ; range split spectrum ; {I}onospheric effect ; {I}onospheric correction ; {T}ime-series analysis ; {EQUATEUR} ; {TRINIDAD} ; {SUMATRA} ; {ZONE} {EQUATORIALE}},
  booktitle = {},
  journal = {{S}cience of {R}emote {S}ensing},
  volume = {9},
  numero = {},
  pages = {100113 [15 p.]},
  ISSN = {2666-0172},
  year = {2024},
  DOI = {10.1016/j.srs.2023.100113},
  URL = {https://www.documentation.ird.fr/hor/fdi:010088857},
}