• 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 The VALPARESOVALPARESO experiment experiment

Status and overview of the data set collectedStatus and overview of the data set collected

D. Hauser, A. Mouche (CETP)D. Hauser, A. Mouche (CETP)

ENVISAT Calibration Review, Frascati, 9-13 December 2002ENVISAT Calibration Review, Frascati, 9-13 December 2002

ObjectivesObjectives

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 (3340- 3347-3433)

PHAROS BUOY: continuous measurements. Wind speed, and direction, Hs, 1D spectrum already available, 2D spectra to be processsed (and assessed)

VALPARESO DATA SETVALPARESO DATA SET

STORM 21 Flights planned with STORM, 14 performed in conjunction with ASAR data 2 flights (3 Nov, 20 Nov) without SAR acquisition6 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°)

Orbitnumber

Date Day AcquisitionMode of ASAR

requested

Incidence Polar. Airbornedata

3326-D 19-oct 292 Image Mode IS1 HH YES

3340-D 20-oct 293 Image Mode IS3 VV YES

3347-A 20-oct 293 Image Mode IS1 HH YES

3383-D 23-oct 296 Alternate Polar IS3 VV+HV YES

3390-A 23-oct 296 Image Mode IS1 VV YES

3426-D 26-oct 299 Alternate Polar IS2 HH+VV YES

3433-A 26-oct 299 Image Mode IS2 HH NO

3469-D 29-oct 302 Alternate Polar IS3 HH+VV YES

3476-A 29-oct 302 Image Mode IS3 HH YES

3512-D 1-nov 305 Image Mode IS2 HH NO

3519-A 1-nov 305 Alternate Polar IS3 HH+VV NO

3555-D 4-nov 308 Image Mode IS2 VV YES

3619-A 8-nov 311 Image Mode IS1 VV NO

3655-D 11-nov 314 Image Mode IS3 VV YES

3662-A 11-nov 314 Image Mode IS1 VV YES

3698-D 14-nov 317 Alternate Polar IS3 HH+VV YES

3705-A 14-nov 317 Image Mode IS2 HH NO

3741-D 17-nov 320 Image Mode IS2 VV YES

3748-A 17-nov 320 Alternate Polar IS3 HH+VV YES

**3784-D 20-nov 323 Image Mode IS2 VV YES

3791-A 20-nov 323 Image Mode IS3 VV NO

Buoy at the Scilly Islands

Pharos buoy

Typical flight planWith 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 Wind and wave conditionsconditions

At Pharos locationAt Pharos location48°31’N, 5°49’W48°31’N, 5°49’W

0

5

10

15

20

25

290 295 300 305 310 315 320 325 330

PHAROS Buoy wind speed (m/s)

wind speed (m/s)

Julian time

01234567

290 295 300 305 310 315 320 325 330

Pharos Buoy H1/3

H1/3 (m)

Julian time

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

4

6

8

10

12

14

290 295 300 305 310 315 320 325 330

Pharos buoy T1/3

T1/3 (s)

Julian time

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, -4.84 W

Inverted spectrum

Observed Wind: 17 m/s, 230°Retrieved waves:

peak wavelength 220 mPeak direction 110°

HSAR= 3.9 m

0

5

10

15

20

25

30

35

40

0 0,1 0,2 0,3 0,4 0,5

OCTOBER 26, 10 and 11 UTCNon directional wave-height spectra

10 UTC11 UTC

Energy density (m^2/Hz)

Frequency (Hz)

U= 6 to 7 m/sn H1/3=3.3 m

With ASAR (3340) and STORM

0

5

10

15

20

0 0,1 0,2 0,3 0,4 0,5

OCTOBER 26, 22 UTCNon-directional wave height spectrum

Energy density (m^2/Hz)

Frequency (Hz)

U=17 m/s, H1/3=3.2 m

With ASAR (3347)

1D wave weight spectra 1D wave weight spectra on October 26 from on October 26 from

PHAROSPHAROS

CONCLUSIONCONCLUSION

Good data set (although less flights with STORM than planned)Good data set (although less flights with STORM than planned)

Good sea-state situationsGood sea-state situations

Present workPresent work

• • analysis of ASAR imagesanalysis of ASAR images

• • STORM data processing (to obtain wave spectra and radar STORM data processing (to obtain wave spectra and radar cross-section)cross-section)

Waiting for other ASAR dataWaiting for other ASAR data