Satellite Radar Altimetry

Escudier, Philippe; Couhert, Alexandre; Mercier, F.; Mallet, Alain; Thibaut, P.; Tran, N.; Amarouche, L.; Picard, Bruno; Carrère, Loren; Dibarboure, Gérald; Ablain, M.; Richard, Jacques; Steunou, N.; Dubois, Pierre; Rio, Marie-Hélène; Dorandeu, J.

doi:10.1201/9781315151779-1

Cited by 22 publications

(8 citation statements)

References 1 publication

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“…The threshold requirement was set at resolving approximately 20 km wavelengths, or equivalently at a noise threshold of 4 cm 2 /cpkm. Finally, the mission had a goal 3 to achieve a noise level of 1 cm 2 /cpkm.…”

Section: A Ocean Science Key and Driving Requirementsmentioning

confidence: 99%

“…T HE elevation of surface water and its slope relative to a reference surface (e.g., the Earth's geoid) plays an important part in determining the circulation of the ocean [1] and the storage and discharge of fresh water over land surfaces [2]. Up until 2023, the best source for obtaining these data on a global basis was the coordinated use of multiple nadir radar altimeters [3]. Over the ocean, multiple nadir altimeters can be combined to provide a spatial resolution varying between 100 km at mid-altitudes and 800 km in the tropics [1] [4].…”

Section: Introductionmentioning

confidence: 99%

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KaRIn, the Ka-Band Radar Interferometer of the SWOT Mission: Design and in-Flight Performance

Peral,

Esteban-Fernández,

Rodríguez

et al. 2024

IEEE Trans. Geosci. Remote Sensing

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The Surface Water and Ocean Topography (SWOT) mission was recommended by the 2007 National Research Council Decadal Survey to expand on previous altimetry missions like TOPEX/Poseidon. Utilizing wide-swath altimetry technology, SWOT aims to achieve complete coverage of the world's oceans and freshwater bodies through high-resolution elevation measurements. SWOT received approval for implementation in 2016, it was ultimately launched in December 2022, and it is currently delivering preliminary data to the public. The primary instrument in SWOT is the Ka-band Radar Interferometer (KaRIn) which utilizes JPL-developed radar interferometry technology to measure ocean and surface water levels with unprecedented accuracy.This paper focuses on the challenges in designing, testing, and finally commissioning in flight a complex instrument like KaRIn. We also present preliminary flight performance and compare it with ground measurements and simulations. Our analysis indicates that KaRIn meets or exceeds all its requirements, but it has also revealed several interesting and unexpected observations, offering just a glimpse of future scientific discoveries that KaRIn will enable.

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Section: A Ocean Science Key and Driving Requirementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

KaRIn, the Ka-Band Radar Interferometer of the SWOT Mission: Design and in-Flight Performance

Peral,

Esteban-Fernández,

Rodríguez

et al. 2024

IEEE Trans. Geosci. Remote Sensing

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“…It is now 50 years since Skylab, the first satellite altimetry mission, was launched in 1973. This was shortly followed by the GEOS-3 (Geodynamic Experimental Ocean Satellite) and Seasat missions, which spanned 1975Seasat missions, which spanned -1979Seasat missions, which spanned and 1978 Satellites following these first-generation missions have shown improvements on the knowledge acquired and reflect improvements in the technologies developed during the lifespans of their respective predecessors (Escudier et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Global marine gravity gradient tensor inverted from altimetry-derived deflections of the vertical: CUGB2023GRAD

Annan,

Wan,

Hao

et al. 2024

Earth Syst. Sci. Data

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Abstract. Geodetic applications of altimetry have largely been inversions of gravity anomaly. Previous studies of Earth's gravity gradient tensor mostly presented only the vertical gravity gradient (VGG). However, there are six unique signals that constitute the gravity gradient tensor. Gravity gradients are signals suitable for detecting short-wavelength topographic and tectonic features. They are derived from double differentiation of the disturbing potential and hence are susceptible to noise amplification which was exacerbated by low across-track resolution of altimetry data in the past. However, current generation of altimetry observations have improved spatial resolutions, with some better than 5 km. Therefore, this study takes advantage of current high-resolution altimetry datasets to present CUGB2023GRAD, a global (latitudinal limits of ±80°) 1 arcmin model of Earth's gravity gradient tensor over the oceans using deflections of the vertical as inputs in the wavenumber domain. The results are first assessed via Laplace's equation, whereby the resultant residual gradient is virtually zero everywhere. Further analysis at local regions in the Arctic and south Indian oceans showed that Txy, Txz and Tyz are the most dominant gravity gradients for bathymetric studies. This proves that bathymetric signatures in the non-diagonal tensor components are worth exploiting. Bathymetric coherence analysis of Tzz over the Tonga Trench showed strong correlation with multibeam shipboard depths. This study proves that current generation of altimetry geodetic missions can effectively resolve Earth's gravity gradient tensor. The CUGB2023GRAD model data can be freely accessed at https://doi.org/10.5281/zenodo.10511125 (Annan et al., 2024).

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“…30-year records of global sea level variation around the world, with instantaneous sea surface height (SSH) at the centimetric level (i.e. with SSH uncertainties ranging from 3.5-3.7 cm depending on the mission and time span considered; Escudier et al, 2017), leading to uncertainties about global mean sea level (GMSL) trends over the entire altimetry period of around ± 0.4 mm yr −1 within a 90 % confidence level (Ablain et al, 2019). When it comes to local sea level trends, Prandi et al (2021) estimate a mean uncertainties of ± 0.83 mm yr −1 over the 1993-2019 period, with regions where the trend uncertainty exceeds the trend esti-mate.…”

Section: Introductionmentioning

confidence: 99%

Nouméa: a new multi-mission calibration and validation site for past and future altimetry missions?

Chupin,

Ballu,

Testut

et al. 2023

Ocean Sci.

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Abstract. Today, monitoring the evolution of sea level in coastal areas is of importance, since almost 11 % of the world's population lives in low-lying areas. Reducing uncertainties in sea level estimates requires a better understanding of both altimetry measurements and local sea level dynamics. In New Caledonia, the Nouméa lagoon is an example of this challenge, as altimetry, coastal tide gauge, and vertical land motions from global navigation satellite systems (GNSSs) do not provide consistent information. The GEOCEAN-NC 2019 field campaign addresses this issue with deployments of in situ instruments in the lagoon (GNSS buoy, pressure gauge, etc.), with a particular focus on the crossover of one Jason-series track and two Sentinel-3A missions tracks. In this study, we propose a method to virtually transfer the Nouméa tide gauge at the altimetry crossover point, using in situ data from the field campaign. Following the philosophy of calibration and validation (Cal/Val) studies, we derive absolute altimeter bias time series over the entire Jason and Sentinel-3A periods. Overall, our estimated altimeter mean biases are slightly larger by 1–2 cm compared to Corsica and Bass Strait results, with inter-mission biases in line with those of Bass Strait site. Uncertainties still remain regarding the determination of our vertical datum, only constrained by the three days of the GNSS buoy deployment. With our method, we are able to re-analyse about 20 years of altimetry observations and derive a linear trend of −0.2 ± 0.1 mm yr−1 over the bias time series. Compared to previous studies, we do not find any significant uplift in the area, which is more consistent with the observations of inland permanent GNSS stations. These results support the idea of developing Cal/Val activities in the lagoon, which is already the subject of several experiments for the scientific calibration phase of the SWOT wide-swath altimetry mission.

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Satellite Radar Altimetry

Cited by 22 publications

References 1 publication

KaRIn, the Ka-Band Radar Interferometer of the SWOT Mission: Design and in-Flight Performance

KaRIn, the Ka-Band Radar Interferometer of the SWOT Mission: Design and in-Flight Performance

Global marine gravity gradient tensor inverted from altimetry-derived deflections of the vertical: CUGB2023GRAD

Nouméa: a new multi-mission calibration and validation site for past and future altimetry missions?

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