AltiKa: a Ka-band Altimetry Payload and System for Operational Altimetry during the GMES Period

Vincent, Patrick; Steunou, N.; Caubet, E.; Phalippou, L.; Rey, L.; Thouvenot, Éric; Verron, Jacques

doi:10.3390/s6030208

Cited by 68 publications

(42 citation statements)

References 24 publications

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“…From Ku-to Ka-band, the scattering coefficient consequently increases by a factor 55. This leads to a penetration depth over snow surface between 0.1 m and 0.3 m in Ka-band [36]. Analysis performed on the altimeter signal acquired in Ku-and Ka-bands over the Antarctic ice sheet are consistent with this assumption.…”

Section: Complementarity Between Ku and Ka Measurements Over Ice Sheesupporting

confidence: 61%

“…Vincent et al [36] demonstrated the feasibility of such an altimeter but also importantly the need of higher resolution altimetry to address one of the most problematic features of ocean circulation, the mesoscale eddies and fronts. These features are essential to understanding the dynamics of ocean circulation on all space and time scales and theoretical studies of the cascade of energy over scales from 100-1000 km have always suffered from the lack of high-resolution observations.…”

Section: Discussionmentioning

confidence: 99%

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The Benefits of the Ka-Band as Evidenced from the SARAL/AltiKa Altimetric Mission: Quality Assessment and Unique Characteristics of AltiKa Data

et al. 2018

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Abstract:The India-France SARAL/AltiKa mission is the first Ka-band altimetric mission dedicated to oceanography. The mission objectives are primarily the observation of the oceanic mesoscales but also include coastal oceanography, global and regional sea level monitoring, data assimilation, and operational oceanography. The mission ended its nominal phase after 3 years in orbit and began a new phase (drifting orbit) in July 2016. The objective of this paper is to provide a state of the art of the achievements of the SARAL/AltiKa mission in terms of quality assessment and unique characteristics of AltiKa data. It shows that the AltiKa data have similar accuracy at the centimeter level in term of absolute water level whatever the method (from local to global) and the type of water surfaces (ocean and lakes). It shows also that beyond the fact that AltiKa data quality meets the expectations and initial mission requirements, the unique characteristics of the altimeter and the Ka-band offer unique contributions in fields that were previously not fully foreseen.

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Section: Complementarity Between Ku and Ka Measurements Over Ice Sheesupporting

confidence: 61%

Section: Discussionmentioning

confidence: 99%

The Benefits of the Ka-Band as Evidenced from the SARAL/AltiKa Altimetric Mission: Quality Assessment and Unique Characteristics of AltiKa Data

et al. 2018

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“…Everywhere else, the elevations from SARAL/AltiKa are 0 to 0.5 m, higher than those of ENVISAT. This pattern confirms that the penetration depth in the Ka-band is lower than in the Ku-band [31]. However, because SARAL/AltiKa and ENVISAT have a different frequency, gain pattern, and crossover points in radar altimetry, the polarization of the antenna is a problem [33].…”

Section: Saral/altika the First Preliminary Resultssupporting

confidence: 56%

“…Moreover, the Ka bandwidth is 480 MHz instead of 320 MHz; thus, the leading edge will be better sampled. In addition, we benefit from less penetration into the snowpack; theoretical calculations estimate less than one meter of penetration depth instead of 5 to 10 m in the Ku-band [31]. For the first time ever, AltiKa observes the surfaces at nadir in a simultaneously active/passive manner.…”

Section: Saral/altika the First Preliminary Resultsmentioning

confidence: 99%

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Study of the Penetration Bias of ENVISAT Altimeter Observations over Antarctica in Comparison to ICESat Observations

2014

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Abstract:The aim of this article is to characterize the penetration bias of the ENVIronmental SATellite (ENVISAT) radar altimeter over the Antarctic ice sheet through comparison with the more accurate measurements of the Ice, Cloud and land Elevation Satellite (ICESat) altimeter at crossover points. We studied the difference between ENVISAT and ICESat fluctuations over six years. We observed the same patterns between the leading edge width and the elevation difference. Both parameters are linked, and the major bias is due to the lengthening of the leading edge width due to the radar penetration. We show that the elevation difference between both altimeters and the leading edge width are linearly well-linked with a 0.8 Pearson correlation coefficient, whereas the slope effect over the coasts is difficult to analyze. When we analyze each crossover point temporal evolution locally, the linear correlation between the leading edge width and the elevation difference is between −0.6 and −1. Fitting a linear model between them, we find a reliability index greater than 0.7 for the Antarctic Plateau and Dronning Maud Land, which confirms that the penetration effect has a linear influence on the retrieved height. Moreover, we present results from SARAL/AltiKa (launched in February 2013) that confirm SARAL/AltiKa accuracy and the promising information it will provide.

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Mesoscale resolution capability of altimetry: Present and future

et al. 2016

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Wavenumber spectra of along‐track Sea Surface Height from the most recent satellite radar altimetry missions [Jason‐2, Cryosat‐2, and SARAL/Altika) are used to determine the size of ocean dynamical features observable with the present altimetry constellation. A global analysis of the along‐track 1‐D mesoscale resolution capability of the present‐day altimeter missions is proposed, based on a joint analysis of the spectral slopes in the mesoscale band and the error levels observed for horizontal wavelengths lower than 20km. The global sea level spectral slope distribution provided by Xu and Fu () with Jason‐1 data is revisited with more recent altimeter missions, and maps of altimeter error levels are provided and discussed for each mission. Seasonal variations of both spectral slopes and altimeter error levels are also analyzed for Jason‐2. SARAL/Altika, with its lower error levels, is shown to detect smaller structures everywhere. All missions show substantial geographical and temporal variations in their mesoscale resolution capabilities, with variations depending mostly on the error level change but also on slight regional changes in the spectral slopes. In western boundary currents where the signal to noise ratio is favorable, the along‐track mesoscale resolution is approximately 40 km for SARAL/AltiKa, 45 km for Cryosat‐2, and 50 km for Jason‐2. Finally, a prediction of the future 2‐D mesoscale sea level resolution capability of the Surface Water and Ocean Topography (SWOT) mission is given using a simulated error level.

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AltiKa: a Ka-band Altimetry Payload and System for Operational Altimetry during the GMES Period

Cited by 68 publications

References 24 publications

The Benefits of the Ka-Band as Evidenced from the SARAL/AltiKa Altimetric Mission: Quality Assessment and Unique Characteristics of AltiKa Data

The Benefits of the Ka-Band as Evidenced from the SARAL/AltiKa Altimetric Mission: Quality Assessment and Unique Characteristics of AltiKa Data

Study of the Penetration Bias of ENVISAT Altimeter Observations over Antarctica in Comparison to ICESat Observations

Mesoscale resolution capability of altimetry: Present and future

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