First Experiences with Active C-Band Radar Reflectors and Sentinel-1

Gisinger, Christoph; Eineder, Michael; Brcic, Ramon; Balss, Ulrich; Gruber, Thomas; Oikonomidou, Xanthi; Heinze, Markus

doi:10.1109/igarss39084.2020.9324381

Cited by 2 publications

(2 citation statements)

References 7 publications

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“…R ADAR transponders are active electronic devices that receive a radar signal, amplify it, and transmit it back to its source, such as a satellite carrying a Synthetic Aperture Radar (SAR) antenna. They can serve as a compact alternative to corner reflectors (CR) for precise SAR positioning [1], [2], SAR interferometry (InSAR), deformation monitoring over areas with few natural coherent scatterers [3], InSAR datum connection, and geodetic data integration to provide an absolute reference to the inherently relative InSAR measurements [4].…”

Section: Introductionmentioning

confidence: 99%

On the Efficacy of Compact Radar Transponders for InSAR Geodesy: Results of Multiyear Field Tests

Czikhardt

Marel²,

Papčo

et al. 2022

IEEE Trans. Geosci. Remote Sensing

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Compact and low-cost radar transponders are an attractive alternative to corner reflectors (CR) for SAR interferometric (InSAR) deformation monitoring, datum connection, and geodetic data integration. Recently, such transponders have become commercially available for C-band sensors, which poses relevant questions on their characteristics in terms of radiometric, geometric, and phase stability. Especially for extended time series and for high-precision geodetic applications, the impact of secular or seasonal effects, such as variations in temperature and humidity, has yet to be proven. Here we address these challenges using a multitude of short baseline experiments with four transponders and six corner reflectors deployed at test sites in the Netherlands and Slovakia. Combined together, we analyzed 980 transponder measurements in Sentinel-1 time series to a maximum extent of 21 months. We find an average Radar Cross Section (RCS) of over 42 dBm 2 within a range of up to 15 degrees of elevation misalignment, which is comparable to a triangular trihedral corner reflector with a leg length of 2.0 m. Its RCS shows temporal variations of 0.3-0.7 dBm 2 (standard deviation) which is partially correlated with surface temperature changes. The precision of the InSAR phase double-differences over short baselines between a transponder and a stable reference corner reflectors is found to be 0.5-1.2 mm (one sigma). We observe a correlation with surface temperature, leading to seasonal variations of up to ±3 mm, which should be modeled and corrected for in high precision InSAR applications. For precise SAR positioning, we observe antenna-specific constant internal electronic delays of 1.2-2.1 m in slant-range, i.e., within the range resolution of the Sentinel-1 IW product, with a temporal variability of less than 20 cm. Comparing similar transponders from the same series, we observe distinct differences in performance. Our main conclusion is that these characteristics are favorable for a wide range of geodetic applications. For particular demanding applications, individual calibration of single devices is strongly recommended.

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Section: Introductionmentioning

confidence: 99%

On the Efficacy of Compact Radar Transponders for InSAR Geodesy: Results of Multiyear Field Tests

Czikhardt

Marel²,

Papčo

et al. 2022

IEEE Trans. Geosci. Remote Sensing

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show abstract

“…The RF chain consists of three amplifiers and a pair of bandpass filters (4.9-6.2 GHz) before and after each amplifier to avoid interference from other devices, such as WiFi networks. With an expected overall RF gain of 50 dB, the expected RCS of the transponders is 44 dBm 2 . The characteristics of the used transponders are summarized in Table I.…”

Section: Radar Transpondersmentioning

confidence: 99%

On the Efficacy of Compact Radar Transponders for InSAR Geodesy: Results of Multi-year Field Tests

Czikhardt¹,

Marel²,

Papčo³

et al. 2022

Preprint

View full text Add to dashboard Cite

Compact and low-cost radar transponders are an attractive alternative to corner reflectors (CR) for SAR interferometric (InSAR) deformation monitoring, datum connection, and geodetic data integration.Recently, such transponders have become commercially available for C-band sensors, which poses relevant questions on their characteristics in terms of radiometric, geometric, and phase stability. Especially for extended time series and for high-precision geodetic applications, the impact of secular or seasonal effects, such as variations in temperature and humidity, has yet to be proven.Here we address these challenges using a multitude of short baseline experiments with four transponders and six corner reflectors deployed at test sites in the Netherlands and Slovakia. Combined together, we analyzed 980 transponder measurements in Sentinel-1 time series to a maximum extent of 21 months.We find an average Radar Cross Section (RCS) of over 42 dBm2 within a range of up to 15 degrees of elevation misalignment, which is comparable to a triangular trihedral corner reflector with a leg length of 2.0 m. Its RCS shows temporal variations of 0.3--0.7~dBm2 (standard deviation) which is partially correlated with surface temperature changes.The precision of the InSAR phase double-differences over short baselines between a transponder and a stable reference corner reflectors is found to be 0.5-1.2 mm (one sigma). We observe a correlation with surface temperature, leading to seasonal variations of up to +/-3 mm, which should be modeled and corrected for in high precision InSAR applications. For precise SAR positioning, we observe antenna-specific constant internal electronic delays of 1.2-2.1 m in slant-range, i.e., within the range resolution of the Sentinel-1 Interferometric Wide Swath (IW) product, with a temporal variability of less than 20~cm.Comparing similar transponders from the same series, we observe distinctdifferences in performance. Our main conclusion is that these characteristics are favorable for a wide range of geodetic applications. For particular demanding applications, individual calibration of single devices is strongly recommended.

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First Experiences with Active C-Band Radar Reflectors and Sentinel-1

Cited by 2 publications

References 7 publications

On the Efficacy of Compact Radar Transponders for InSAR Geodesy: Results of Multiyear Field Tests

On the Efficacy of Compact Radar Transponders for InSAR Geodesy: Results of Multiyear Field Tests

On the Efficacy of Compact Radar Transponders for InSAR Geodesy: Results of Multi-year Field Tests

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