ESA's ground breaking synthetic aperture radar: the ENVISAT-1 ASAR active antenna

Torres, Ramón; Buck, Christopher; Guijarro, J.; Suchail, J.-L.

doi:10.1109/aps.1999.788235

Cited by 3 publications

(2 citation statements)

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“…( 1) and ( 2). The values of the radiometric stability (0.50 dB) and the radiometric accuracy (0.57 dB) are listed in Torres et al (1999). Assuming all errors are independent and can be summed, we estimated that the confidence interval at 1 standard deviation of ASAR measurements over 5 ha areas ranges from ±0.86 dB for images acquired at IS1 to ±0.82 dB for images acquired at IS6.…”

Section: Envisat-asar Datamentioning

confidence: 99%

“…In the microwave spectral domain, the ASAR radar onboard the Envisat mission is an active instrument operating at C-band with a 30 m spatial resolution in the Alternating Polarisation mode. The orbit cycle is 35 days, but the combination of acquisitions at different incidence angles allows revisiting of a few days (Torres et al, 1999). The continuity of combined high resolution and repetitivity data sets in the microwave and the optical spectral domains is insured in the near future by the planned launch of Sentinel-1 and Sentinel-2 satellite missions (ESA, 2007, cited in Hagolle et al, 2008.…”

Section: Introductionmentioning

confidence: 99%

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Combined use of optical and radar satellite data for the monitoring of irrigation and soil moisture of wheat crops

Fieuzal¹,

Duchemin²,

Jarlan³

et al. 2010

Preprint

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The objective of this study is to get a better understanding of radar signal over irrigated wheat fields and to assess the potentialities of radar observations for the monitoring of soil moisture. Emphasis is put on the use of high spatial and temporal resolution satellite data (ENVISAT/ASAR and FORMOSAT-2). Time series of images were collected over the Yaqui irrigated area (Mexico) throughout one agricultural season from December 2007 to May 2008, together with measurements of soil and vegetation characteristics and agricultural practices. The comprehensive analysis of these data indicates that the sensitivity of the radar signal to vegetation is masked by the variability of soil conditions. On-going irrigated areas can be detected all over the wheat growing season. The empirical algorithm developed for the retrieval of topsoil moisture from ENVISAT/ASAR images takes advantage of the unique capabilities of the FORMOSAT-2 instrument to monitor the seasonality of wheat canopies. Topsoil moisture estimates are scattered at the timing of plant emergence and during plant senescence. Estimates are much more accurate from tillering to grain filling stages with an absolute error about 9% (0.09 m3 m−3, 35% in relative value). This result is attractive since topsoil moisture is estimated at a high spatial resolution (i.e. over subfields of about 5 ha) for a large range of biomass water content (from 5 and 65 t ha−1) independently from the viewing angle of ASAR acquisition (incidence angles IS1 to IS6)

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Section: Envisat-asar Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%