1. Validation of radiometric models and simulated KaRIn/SWOT data based on ground and airborne acquisitions
Page de titre, mentionner contributions Altamira et Cap
Roger Fjørtoft, Jean-Claude Lalaurie, Nadine Pourthie, Christine Lion, Jean-Marc Gaudin, Alain Mallet (CNES, Toulouse, France),
Jean-François Nouvel, Pierre Borderies (ONERA, Toulouse/Salon de Provence, France),
Pascal Kosuth (CEMAGREF, Montpellier, France),
Christian Ruiz (Capgemini, Toulouse, France).
IGARSS 2011, Vancouver, Canada, July 2011

2. Outline Introduction Modeling and simulation Airborne acquisitions
Context, objectives
Specificities of KaRIn/SWOT interferometric SAR data
Modeling and simulation
Backscattering from various surfaces
Simulation of raw and SLC radar images
Airborne acquisitions
First interferometric Ka-band acquisitions including the KaRIn incidence range (1-4°)
Near-field Ka-band measurements
Water backscattering as a function of wind speed and surface roughness
IGARSS 2011, Vancouver, Canada, July 2011

3. Introduction
Context
Original InSAR configuration of KaRIn/SWOT: Ka-band, near-nadir (1-4°)
Very limited bibliography on backscattering from natural surfaces
Modeling of Ka-band backscattering (0)
As a function of surface type, surface conditions, incidence angle, …
Simulation of raw (L0) and SLC (L1) KaRIn/SWOT interferometric data
Radiometry and geometry
Objective: Realize airborne and near-field Ka-band acquisitions
Compare models and simulations with real data (validate, improve)
Need for ground truth
Study important phenomena w.r.t. feasibility and performance
Coherence, land/water contrast, layover, …
Enable more realistic input data for algorithm development and testing
Airborne data and improved simulated images
IGARSS 2011, Vancouver, Canada, July 2011

4. BUSARD/DRIVE airborne acquisitions (1/2)
BUSARD is a Stemme motor-glider operated by ONERA
DRIVE Ka-band radar integrated in POD
Interferometry with short (18 cm) or long (4.7 m) baseline
2.5 W amplifier
Near-nadir acquisitions (0-14°) with 18 cm baseline in 2011
Altitude: 3000 m (9500 ft)
Swath: 700 m
Acquisition length: 5 km (2 min)
PRF: 1250 Hz
Integration time: 0.2 s
IGARSS 2011, Vancouver, Canada, July 2011

5. BUSARD/DRIVE airborne acquisitions (2/2)
Simultaneous ground truth:
Wind speed
Water surface roughness
Water surface height and slope
Wave height (buoys)
Soil humidity
Same day/week/month:
Soil roughness
Vegetation characteristics
Landcover
Available static data:
Digital maps
DEM
IGARSS 2011, Vancouver, Canada, July 2011

6. Acquisition sites in the Camargue area (2011)
Rhône
Vaccarès
Espiguette (buoy)
Piemanson
IGARSS 2011, Vancouver, Canada, July 2011

7. DRIVE/BUSARD acquisition 24/02/2011 (Rhône)
voie a 0° 0°
~1°
~4°
Artifacts due to wide antenna lobe (right/
left contamination)
~700 m
~10°
Trihedrals
~2,6 km
13°
Amplitude
IGARSS 2011, Vancouver, Canada, July 2011 7

8. DRIVE/BUSARD acquisition 24/02/2011 (Rhône)
Phase (interferogram)
IGARSS 2011, Vancouver, Canada, July 2011

9. DRIVE/BUSARD acquisition 24/02/2011 (Rhône)
~0.3
>0.9
~0.7
Coherence
IGARSS 2011, Vancouver, Canada, July 2011

10. DRIVE/BUSARD acquisition 14/04/2011 (Vaccarès)
Amplitude
IGARSS 2011, Vancouver, Canada, July 2011

11. DRIVE/BUSARD acquisition 14/04/2011 (Vaccarès)
Amplitude 1
Amplitude 2
Coherence
Phase
IGARSS 2011, Vancouver, Canada, July 2011

12. DRIVE/BUSARD acquisition 14/04/2011 (Espiguette)
Amplitude
IGARSS 2011, Vancouver, Canada, July 2011

13. DRIVE/BUSARD acquisition 14/04/2011 (Espiguette)
Amplitude 1
Amplitude 2
Coherence
Phase
IGARSS 2011, Vancouver, Canada, July 2011

14. DRIVE/BUSARD acquisition 25/05/2011 (Rhône)
Amplitude
IGARSS 2011, Vancouver, Canada, July 2011

15. Near-field measurements in Ka-band (1/2)
Near-field Ka-band measurements of 0 of water with a network analyzer and an automatically steerable (0-10°) parabolic antenna (ONERA)
Simultaneous measurement of water surface roughness (using immerged pressure sensors) and wind speed (CEMAGREF)
Rapidly varying wind conditions make the interpretation of the first results complicated.
IGARSS 2011, Vancouver, Canada, July 2011

16. Near-field measurements in Ka-band (2/2)
Acquisitions in the Large Air-Sea Interaction Facility (LASIF) at IRPHE (Luminy): 40 m wind tunnel + 40 m water tank
Possibility to study wind-generated water roughness (waves) in stable conditions (as well as to add mechanically generated waves)
Additional equipment for optical roughness characterization (IRPHE)
Comparison of 0 profiles with radiometric models (CapGemini)
IGARSS 2011, Vancouver, Canada, July 2011

17. Water 0 as a function of wind speed
Wind perpendicular to incidence direction
0 (dB)
Incidence (°/100)
Wind parallel to incidence direction
0 (dB)
Incidence (°/100)
IGARSS 2011, Vancouver, Canada, July 2011

18. Conclusion Airborne acquisitions with DRIVE/BUSARD
First interferometric Ka-band acquisitions including the near-nadir incidence range of KaRIn/SWOT (1-4°)
Confirmation of main feasibility and measurement physics assumptions
Will allow to refine models and simulators
Experience gained w.r.t. InSAR processing and ground truth collection
Hydrology, coastal and ocean test sites covered; possible extension to other surface types: forest, snow/ice, …
Near field measurements of water surfaces
0 as a function of incidence and wind speed / surface roughness
Interesting phenomena observed; comparison with models ongoing
Wind-generated roughness only; possibility of adding waves mechanically
Complementary in situ and wind/water tank measurements
IGARSS 2011, Vancouver, Canada, July 2011