Day 4

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Paper title Wave observations with the Earth Explorer 10 candidate Harmony
Authors
  1. Marcel Kleinherenbrink Delft University of Technology (TU Delft) Speaker
  2. Frederic Nouguier Ifremer
  3. Alexis Mouche IFREMER
  4. Antoine Grouazel IFREMER
  5. Bertrand Chapron Ifremer - LOPS
  6. Paco López-Dekker Delft University of Technology (TU Delft)
Form of presentation Poster
Topics
  • A8. Ocean
    • A8.14 Remote-sensing of Ocean Waves and their Applications
Abstract text Harmony consists of two satellites that will fly in a constellation with one of the Sentinel-1 satellites. The two Harmony satellites carry a passive instrument that receives signals which are transmitted by Sentinel-1 and reflected from the surface. The full system therefore benefits from two additional lines-of-sight, which enables the vectorization of high-resolution wind stress and surface motion. It also provides a better spectral coverage and therefore a better constraint on the long-wave spectrum.

This presentation will discuss the mapping of ocean wave spectrum into a bi-static SAR spectrum. This work will rely on different and coherent approaches. First, We will present a theoretical analysis extending the historical mono-static closed-form equation (Hasselmann and Hasselmann [1991], Krogstad [1992], Engen and Johnsen [1995]) and relying on bistatic transfer functions and bi-static configuration. This approach allows an easier understanding and interpretable analysis of the bi-static SAR mapping of ocean wave spectra.
This theoretical closed-form equation will be exploited and compared to numerical instrumental simulations which mimics as physically as possible the full observation chain of a prescribed ocean scene. Despite the high computational cost, these simulations offer a much larger panel of possibilities to look at instrumental and sea-state-parameter impacts on the resulting SAR spectra. The bi-static specifications will be emphasized and compared to the mono-static equivalent configuration in order to demonstrate the benefits of Harmony in terms of wave retrieval.

To corroborate the findings of the combined theoretical and numerical analysis, we will rely on existing Sentinel-1 data acquired on the same ocean scene at a slightly different time during consecutive ascending and descending passes. These co-located mono-static acquisitions are not fully equivalent to a multi-static SAR configuration as Harmony, but are representative of, and give insight into, the valuable azimuthal diversity gain to better retrieve the directional properties of ocean wave spectrum.

The three approaches previously presented will show that the additional lines-of sight benefits the retrieval of the wave spectrum. The bi-static companions are sensitive to waves traveling in different directions, which makes the RAR spectral analysis of high interest to the study of wind wave characteristics. The ratios of the intensities vary with direction and wave number and therefore bi-static companions provide new means to help retrieve the directional surface-wave spectrum. The SAR transform is more complex. Still, compared to the mono-static transform the bi-static transform displays improved capabilities, particularly in terms of a larger spectral coverage.