In February 2011, first campaign for SWOT  preparation

1. objectives

The instrument that will fly on board SWOT is a radar interferometer in Ka Band. There is few studies of  retrodiffusion by natural surfaces in this frequency band, in peculiar for a near nadir geometry. These studies are concerning a low diversity of surface types and small number of associated parameters (with narrow variation range)  : incidence angle, soil humidity and rugosity, and over sea, water salinity and waves height.

Simulators have been developped by  JPL and CNES, taking into account radiometric and geometric aspects.  It is necessary to validate these results using ground truth in flight measurements.

2. means

2.1 the instrument

During the campaign, DRIVE radar flying on  board moto glidder BUSARD, both ONERA means,  have been operated.

DRIVE and BUSARD on ONERA website (in French)

DRIVE is a  band Ka radar. It is operated in interferometric mode short base (18 cm) or long base (4,7 m) .

Flying altitude is 3000m and swath path is  700m. Measurements are acquired along 5 km segments (2 minutes).

2.2 Observation site

The  DRIVE/BUSARD campaign for SWOT was operated during the first 2011 semestre in Camargue.Space measurements has been coupled  with ground  measurements for wind speed, water and soil rugosity,  soil wetness, vegetation parameters, as welle as altitude and slopes measurements, allowing comparisons with models and simulations.

Interferometrics measurements were settled above several sites : Rhône river south Arles, coast at Piemanson and around a buoy in the  Mediterranean sea.

3. résults

First acquisition in  Ka band,  incidences from 0 to 14°
(concerning KaRIn/SWOT, incidences will be between 0.6°  and  4.1°)

The radar image is nearly  1800 m long and 750m wide. Vertical mesurements are at the top of the image and the bottom corresponds to incidence 14°.

La bright zone is Rhône river and "berges" are darker.

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