Abstract's details
Characterization of the Errors of Sentinel-3A Small Scale Content in SAR mode
CoAuthors
Event: 2017 Ocean Surface Topography Science Team Meeting
Session: Quantifying Errors and Uncertainties in Altimetry data
Presentation type: Type Poster
Contribution: not provided
Abstract:
The ESA (European Space Agency) mission Sentinel-3A was successfully launched in February 2016. Sentinel-3A is a multi-instrument mission to measure sea-surface topography, sea- and land-surface temperature, ocean colour and land colour with high-end accuracy and reliability.
The SRAL (Sentinel Radar Altimeter) sensor on board Sentinel-3A differs from previous conventional pulse limited altimeters by providing observations with the Synthetic Aperture Radar mode (SARM). The SARM (or Delay Doppler mode) full coverage was activated over the global ocean since the 12th April 2016 and it is available at global scale for the very first time in the altimetry history. Important benefits from the SARM are expected by the scientific community thanks to the improved precision and resolution offered by this technique.
It was already evidenced with Cryosat-2 analysis over SAR regions that the SARM provides a different content of seal level for scales below 60 km, compared to conventional altimetry. While LRM spectrum exhibits a bump signature, SARM spectrum of sea level does not have this artefact. Labroue et al showed in 2015 that a spectral slope different from the continuous decay from large scales to shorter ones was present on SARM data processed for Cryosat-2, but this analysis was restricted to the Agulhas region. More recently, Raynal et al confirmed that the spectral content of Sentinel-3A mission in SARM also contains an error for scales below 60 km. Thanks to the global coverage of Sentinel-3A mission, part of the error was assumed to come from the inaccuracy of the Mean Sea Surface under Sentinel-3A ground track. This assumption is quantified more precisely in the present study. The question still pending on the source of the red noise present on highest frequencies of the SARM spectrum is also revisited.
We further detail the assessment of the signal detected on Sentinel-3A at these scales and discuss the potential of this technique for improving the observation of the small scale ocean content.
The SRAL (Sentinel Radar Altimeter) sensor on board Sentinel-3A differs from previous conventional pulse limited altimeters by providing observations with the Synthetic Aperture Radar mode (SARM). The SARM (or Delay Doppler mode) full coverage was activated over the global ocean since the 12th April 2016 and it is available at global scale for the very first time in the altimetry history. Important benefits from the SARM are expected by the scientific community thanks to the improved precision and resolution offered by this technique.
It was already evidenced with Cryosat-2 analysis over SAR regions that the SARM provides a different content of seal level for scales below 60 km, compared to conventional altimetry. While LRM spectrum exhibits a bump signature, SARM spectrum of sea level does not have this artefact. Labroue et al showed in 2015 that a spectral slope different from the continuous decay from large scales to shorter ones was present on SARM data processed for Cryosat-2, but this analysis was restricted to the Agulhas region. More recently, Raynal et al confirmed that the spectral content of Sentinel-3A mission in SARM also contains an error for scales below 60 km. Thanks to the global coverage of Sentinel-3A mission, part of the error was assumed to come from the inaccuracy of the Mean Sea Surface under Sentinel-3A ground track. This assumption is quantified more precisely in the present study. The question still pending on the source of the red noise present on highest frequencies of the SARM spectrum is also revisited.
We further detail the assessment of the signal detected on Sentinel-3A at these scales and discuss the potential of this technique for improving the observation of the small scale ocean content.