Analyze the information brought by the polarization diversity (HH-VV-HV for ASAR, full-polarimetric for airborne radar) for wind and wave studies Validate and improve (if possible) the inversion algorithm used to estimate wave spectra from SAR (level 2 algorithm) Extend inversion algorithms to configurations other than IM2, VV The VALPARESO experiment Status and overview of the data set collected D. Hauser, A. Mouche (CETP) ENVISAT Calibration Review, Frascati, 9-13 December 2002 Objectives

Procedure: Flights performed with the airborne polarimetric radar STORM, in conjunction with ASAR acquisitions in Image Mode (IS1,IS2, IS3, AP3), different polarizations In situ measurements: wind and waves at two locations within the ASAR and STORM swath (PHAROS buoy + Scilly) Archive of wave model predictions (WAM, VAG) Location of the experiment: Near Atlantic and English Channel (flights from Brest, Brittany, France) Dates: 19 October-21 November 2002

ASAR: 21 set of ASAR data requested, 20 scheduled (One cancelled- orbit 3781) due to Leonides meteor 3 ASAR data sets already provided by ESA ( ) PHAROS BUOY: continuous measurements. Wind speed, and direction, Hs, 1D spectrum already available, 2D spectra to be processsed (and assessed) VALPARESO DATA SET STORM 21 Flights planned with STORM, 14 performed in conjunction with ASAR data 2 flights (3 Nov, 20 Nov) without SAR acquisition 6 cancellation of flights with STORM due to meteorological conditions (5) or aircraft problem (1)

=> Full polarimetric information => breaking?? STORM instrument: Polarimetric radar using a real-aperture system, same frequency as ASAR STORM data analysis => Wave spectra (without the limitation of SAR due to velocity bunching)- Hauser et al, 1992  - Radar Cross-section in HH, VV,HV at incidence angles from 5 to 35° or from 20 to 55° (more limited range in HV)  Wind speed (from empirical models such as C-mod)) and wind direction  Information on hydrodynamic modulation (Hauser et al, 1996), useful for SAR analysis at moderate incidence angles (≥20°)

Buoy at the Scilly IslandsPharos buoy Typical flight plan With the STORM radar 11 November 18:40-20:40 Coincident ASAR data: orbit 3662, 21:50 TU Im1,VV (waiting for the ASAR data to be processed

20 October 2002, orbit 3340, descending pass, 10:23:51, IM3-VV (Data received) Airborne radar measurements Pharos buoy

Wind and wave conditions At Pharos location 48°31’N, 5°49’W 26 October 10 cases of ASAR data sets (among 20) in conditions of wind > 10 m/s and wave height > 2 m 9 with STORM data

Significant period of the waves

Preliminary attempt to retrieve the wave spectrum from a subset of SLC image => orbit 3433 (Im2-HH) (A. Mouche) adaptation of the inversion algorithm provided by IFREMER and NORUT to the image case !! VERY PRELIMINARY

26 October 21:56, Orbit 3433

Extraction from ASAR SLC Image (IS2-HH) Orbit 3433, Location 49.15N, W Inverted spectrum Observed Wind: 17 m/s, 230° Retrieved waves: peak wavelength 220 m Peak direction 110° H SAR = 3.9 m

With ASAR (3340) and STORM With ASAR (3347) 1D wave weight spectra on October 26 from PHAROS

CONCLUSION Good data set (although less flights with STORM than planned) Good sea-state situations Present work analysis of ASAR images analysis of ASAR images STORM data processing (to obtain wave spectra and radar cross-section) STORM data processing (to obtain wave spectra and radar cross-section) Waiting for other ASAR data