d. antoine, e. leymarie, a. morel, b. gentili laboratoire d'océanographie de villefranche,...

D. Antoine, E. Leymarie, A. Morel, B. GentiliD. Antoine, E. Leymarie, A. Morel, B. Gentili

Laboratoire d'Océanographie de Villefranche, FranceLaboratoire d'Océanographie de Villefranche, France

J.P. Buis, N. Buis, S. Victori, S. Meunier, M CaniniJ.P. Buis, N. Buis, S. Victori, S. Meunier, M Canini

CIMEL Electronique, ParisCIMEL Electronique, Paris

B. Fougnie, P. HenryB. Fougnie, P. Henry

CNES, Toulouse center, FranceCNES, Toulouse center, France

Anisotropy of the underwater light field: Anisotropy of the underwater light field: development of a “radiance camera”development of a “radiance camera”

http://www.obs-vlfr.fr/Boussole

About 140001-minute acquisition sequences taken at 6Hz, of Es, Ed, Eu, and nadir Lu, at z=4 & 9 meters

Along with wave height, wave period, IOPs and AOPs.

Paper submitted to JGR … waiting for Editor decision

A data set that might be of interest to you in the frame of Radyo

Anisotropy of the underwater light fieldAnisotropy of the underwater light field•Characterized by the “Q factor”:Characterized by the “Q factor”:

)IOPs,,,,(L

)IOPs,,(E)IOPs,,,,(Q

svu

susv

Q is rhe ratio between the upwelling irradiance (EQ is rhe ratio between the upwelling irradiance (Euu) and the upwelling ) and the upwelling

radiance (Lradiance (Luu) measured in a given direction. Q depends on :) measured in a given direction. Q depends on :

The sun positionThe sun position The observation directionThe observation direction

The wavelengthThe wavelength Water optical properties (IOPs)Water optical properties (IOPs)

Knowledge of this “Q factor” is important to Knowledge of this “Q factor” is important to accurately derive the marine reflectance from accurately derive the marine reflectance from the satellite remote sensing measurement at the satellite remote sensing measurement at the top of the atmospherethe top of the atmosphere

I.I. Introduction, Introduction, contextcontext, background, background

Anisotropy of the underwater light fieldAnisotropy of the underwater light field•Q can be derived from RT Simulations (Morel & Gentili, Q can be derived from RT Simulations (Morel & Gentili,

1991, 1993, 1996; Morel et al 2002)1991, 1993, 1996; Morel et al 2002)

The accuracy of such simulations mostly derives from The accuracy of such simulations mostly derives from that of the VSFthat of the VSF

These simulations are partly validated in open ocean These simulations are partly validated in open ocean “Case I waters”“Case I waters”

Still no measurements in coastal “Case II waters”Still no measurements in coastal “Case II waters”

nearly nothing for the downwelling hemispherenearly nothing for the downwelling hemisphere

I.I. Introduction, context, backgroundIntroduction, context, background

II.II. The Radiance CameraThe Radiance Camera

Our general goalOur general goal

- Develop our own instrumentDevelop our own instrument

- Tentatively improve some parts of the design as compared to Tentatively improve some parts of the design as compared to existing instrumentationexisting instrumentation

- Further describe the distribution of the upwelling radiance just Further describe the distribution of the upwelling radiance just beneath the sea surface (bio-optical state, sea state, atmospheric beneath the sea surface (bio-optical state, sea state, atmospheric conditions)conditions)

- Extend the description to various depths within the lit layersExtend the description to various depths within the lit layers

- Extend the description to Case 2 watersExtend the description to Case 2 waters

- Simultaneously measure the upwelling and downwelling Simultaneously measure the upwelling and downwelling hemisphereshemispheres

- Invert the full radiance distribution in terms of the VSF ?Invert the full radiance distribution in terms of the VSF ?


Partnership and project historyPartnership and project history

Mid 2002 : First discussion between LOV, CNES and CIMEL. Mid 2002 : First discussion between LOV, CNES and CIMEL.

Definition of specificationsDefinition of specifications

2003 : 2003 : Project funded by a CNES “Research & Technology” Project funded by a CNES “Research & Technology” actionaction

CIMELCIMEL : Conception (optic, electronic) and realization of the : Conception (optic, electronic) and realization of the cameracamera

LOVLOV : Science background, system specifications, : Science background, system specifications, characterization and validation of the prototype, characterization and validation of the prototype, deployment at seadeployment at sea

2006 : 2006 : Additional funding from CNESAdditional funding from CNES

2008 : 2008 : Test of the first prototypeTest of the first prototype

Specifications of the cameraSpecifications of the camera

Radiometric : Radiometric : - sensitivity better than 10- sensitivity better than 10-5-5 Wm Wm-2-2nmnm-1-1srsr-1-1

- accuracy better than 5%- accuracy better than 5%

- measurement range : 10- measurement range : 10-5-5 to 1 Wm to 1 Wm-2-2nmnm-1-1srsr-1-1

- dynamic over 1 image : 3 decades- dynamic over 1 image : 3 decades

- Multi-spectral in the visible range- Multi-spectral in the visible range

Geometric : Geometric : - Hemispheric field of view (a bit larger actually)- Hemispheric field of view (a bit larger actually)

- angular resolution ~ 1°- angular resolution ~ 1°

Specific : Specific : - integration time < 100 ms (movement caused by - integration time < 100 ms (movement caused by waves)waves)

- Longer integration times as well (very dim light) - Longer integration times as well (very dim light)

- compact design to minimize self-shading- compact design to minimize self-shading

- highly resistant to blooming effect (image of the sun)- highly resistant to blooming effect (image of the sun)


Schematic descriptionSchematic description

Fish eye optic

Bandpass filters (on a filter wheel)

CMOS

CMOS matrix

Aux

Auxiliary sensors

Com

Data transfer & commands

200m depth container

200m electrical/optical cable


Full descriptionFull description

CMOS

Aux

Com

•The Fish Eye Optic :The Fish Eye Optic : Telecentric, non achromaticTelecentric, non achromatic Developed specifically for this Developed specifically for this

applicationapplication Patented by CIMELPatented by CIMEL



CMOS

Aux

Com

•Filters :Filters : The telecentric optic allows a small The telecentric optic allows a small

incidence angle on the filtersincidence angle on the filters Filters used in the camera (Semrock Filters used in the camera (Semrock

®):®):λλ (nm) (nm) ΔΔλλ (nm) (nm)

406406 1515

438438 2424

494494 2020

510510 2020

560560 2525

628628 4040



•Sensor :Sensor :The choice of the sensor to have : dynamic, The choice of the sensor to have : dynamic,

sensitivity and no blooming is a key point for sensitivity and no blooming is a key point for this projectthis project

CDD : Best sensitivity, subject to bloomingCDD : Best sensitivity, subject to bloomingCMOS : less sensitive, more linear, no CMOS : less sensitive, more linear, no

blooming blooming

Our Choice :Our Choice :

a “commercial” CMOS, monochrome, 12 bit a “commercial” CMOS, monochrome, 12 bit digitization, digitization,

HD format (1920 x 1080), pixel size 5 HD format (1920 x 1080), pixel size 5 mm

CMOS

Aux

Com

Main difficulty: trade off between Main difficulty: trade off between specs, cost, availability specs, cost, availability



•Auxiliary sensors :Auxiliary sensors : CompassCompass depth sensordepth sensor tilt sensortilt sensor Internal temperature and humidityInternal temperature and humidity

CMOS

Aux

Com



•Data transferData transfer optical connection (CameraLink®)optical connection (CameraLink®) transfer rate : 15 frames/s (max)transfer rate : 15 frames/s (max) file : 2.3 Mo / frame, Tiff format file : 2.3 Mo / frame, Tiff format

•Instrument commandsInstrument commands RS232 through CameraLink®RS232 through CameraLink®

CMOS

Aux

Com


The first prototype of the LOV-CIMEL Radiance The first prototype of the LOV-CIMEL Radiance CameraCamera

Camera delivered at the end of 2007 :Camera delivered at the end of 2007 :Size (mm): Ø96 * 260Size (mm): Ø96 * 260

weight : 2.4 kgweight : 2.4 kg


Test of the deployment system, 14/03/08 Test of the deployment system, 14/03/08 Test in air Test in air

The first prototype of the LOV-CIMEL Radiance The first prototype of the LOV-CIMEL Radiance CameraCamera


III.III. Initial characterization resultsInitial characterization results

Villefranche Radiometry FacilityVillefranche Radiometry Facility

• 2 darkrooms at the Laboratoire d’Océanographie de 2 darkrooms at the Laboratoire d’Océanographie de VillefrancheVillefranche

• One optical table and large assortment of optomechanic One optical table and large assortment of optomechanic componentscomponents

• 1000 W halogen calibrated Lamps and stabilized power 1000 W halogen calibrated Lamps and stabilized power supplysupply

• Large Spectralon® calibrated reflective targetLarge Spectralon® calibrated reflective target

• Irradiances and radiance calibrated sensorsIrradiances and radiance calibrated sensors

Angular resolutionAngular resolutionComparison between 0 and 1° sightComparison between 0 and 1° sight

6 images (different λ)

PinholeConvex Lens Convex Lens

fBeam div. < 0.5°


Angular resolutionAngular resolution0° sight0° sight


1°1°


sum



0°0°




Angular resolution better than Angular resolution better than 1°1°


Correspondence between a direction in space and a position on the

imager, in theory : θ = k.r (where r is the distance to the center)

Rotation 5° step

Estimation of the distance r(θ,λ) from

peak to center

Geometric characterizationGeometric characterization



angular calibration494 nm

y = 0.1907x

R2 = 0.9993

-100

-75

-50

-25

0

25

50

75

100

-500 -400 -300 -200 -100 0 100 200 300 400 500

distance (pixel)

ang

le (

°)

Data 494nm

Fit linear

Link between a direction and a position on the imager

In theory : θ = k.r (where r is the distance to the center)



angular calibration494 nm

-100

-75

-50

-25

0

25

50

75

100

-500 -400 -300 -200 -100 0 100 200 300 400 500

distance (pixel)

ang

le (

°)

Data 494nm

Fit cubic

Fit linear


,.,. 3 rbra


Angular calibration(all wavelengths)

-100

-75

-50

-25

0

25

50

75

100

-500 -400 -300 -200 -100 0 100 200 300 400 500

distance (pixel)

an

gle 406nm Fit 406

438nm Fit 438

494nm Fit 494

510nm Fit 510

560nm Fit 560

628nm Fit 628



Field of view = ± 92°Field of view = ± 92°


Experimental Setup

2

50

501

d

cmERL cal

cmSpect

Spectralon® target

d

View of the cameraView of the camera

Sensitivity Sensitivity (S/N at low radiance)(S/N at low radiance)


Estimation of radiance range to measure (upwelling flux)

Wm‑2nm‑1sr‑1

Depth : 0-

λ min max

412 nm 5.E-04 5.E-02

560 nm 5.E-04 5.E-02

660 nm 5.E-05 2.E-02

Estimation of radiance intensity with our setup

radiance (Wm‑2nm‑1sr‑1)

406 nm 438 nm 494 nm 560 nm 628 nm

5.40E-04 8.59E-04 1.55E-03 2.52E-03 3.47E-03

SensitivitySensitivity(S/N at low radiance)(S/N at low radiance)

We are in low radiance configuration at We are in low radiance configuration at 406nm406nm


SensitivitySensitivity(S/N at low radiance)(S/N at low radiance)

Methodology :

1. Acquisition of 20 images, for each λ, exposure 100 ms

2. Extraction of 16 pixels (4*4 square) in the middle of the target

3. Calculating of ΔCount for 1 pixel over 20 images. Gives S/N (1 pixel)

4. Calculating of ΔCount for 16 pixels over 20 images. Gives S/N (16 pixels)

406 nm 438 nm 494 nm 560 nm 628 nm

S/N (1 pixel) 14.7 31.8 49.2 86.6 170.1

S/N (16 pixels) 62.8 145.6 166.6 314.3 604.9


Rolloff of the fish-eye opticsRolloff of the fish-eye optics

Definition : Rolloff of a lens is the attenuation of radiance on increase in view angle. It depends on :

• Optic’s attenuation• Variation of dΩ view by each pixel

Plaque Spectralon

d


Spectralon®target

d



L

θ90°-90°



Rolloff for differents λ

0.6

0.7

0.8

0.9

1

1.1

-100 -50 0 50 100

angle

No

rmal

ised

In

ten

sity

406 nm

438 nm

494 nm

560 nm

628 nm



Q factor measurementQ factor measurement

IV.IV. Preliminary field resultsPreliminary field results

Q Measurement:Q Measurement:Cruise : “SORTIE”Cruise : “SORTIE”Date : 17 oct 2008 – Date : 17 oct 2008 – 13h30 UT13h30 UTLocation: BOUSSOLELocation: BOUSSOLESun Zenith : 61.2° - Blue Sun Zenith : 61.2° - Blue SkySky560nm, integration time 560nm, integration time : 90ms: 90ms

““SORTIE” cruise: PI C. SORTIE” cruise: PI C. Trees, 2 weeks in Trees, 2 weeks in October 2008 in the October 2008 in the Mediterranean SeaMediterranean Sea

15

30

45

60

90

0 50 100 150 200 250 300

05

01

00

15

02

00

25

0

15

30

45

60

90

0 1 2 3 4 5

wave 560 - tilt: 1.5 H: 133056 - Qn: 3.31 1.5

Q

Q nadir comparisonQ nadir comparison


Q comparison:Q comparison:Cruise : NATOCruise : NATODate : 26 oct 2008 Date : 26 oct 2008 – 13h30 UT– 13h30 UTPlace : SW PisaPlace : SW PisaSun Zenith : 61° - Sun Zenith : 61° - Blue SkyBlue Sky

““SORTIE” cruise: SORTIE” cruise: PI C. Trees, 2 PI C. Trees, 2 weeks in October weeks in October 2008 in the 2008 in the Mediterranean Mediterranean SeaSea

Q nadir Comparison 2008-10-26 Arno Plume

4

4.5

5

5.5

6

6.5

7

350 400 450 500 550 600 650 700

Wavelength (nm)

Q f

ac

tor

(sr)

SAtlantic hyper

SAtlantic hyper

JRC SAtlantic Multi

JRC SAtlantic Multi

LOV Camera S28

Qnadir comparisons between the camera and SAtlantic’s free fall profilersQnadir comparisons between the camera and SAtlantic’s free fall profilers

Q factor comparisonQ factor comparison


Q comparison:Q comparison:Cruise : Optic-MedCruise : Optic-MedDate : 5,7 and 8 Mai Date : 5,7 and 8 Mai 2008 2008 Place : Mediterranean Place : Mediterranean seaseaBlue Sky, coastal blue Blue Sky, coastal blue waterswaters[Chla] : 0.116-1.24 [Chla] : 0.116-1.24 mg.mmg.m-3-3

““Optic-Med” cruise: 2 Optic-Med” cruise: 2 weeks in April 2008, in weeks in April 2008, in the Mediterranean Seathe Mediterranean Sea

3.0 3.5 4.0 4.5 5.0 5.5 6.0

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Q nadir mod

Q n

ad

ir m

ea

s

ooooo

406 nm438 nm494 nm560 nm628 nm

Qnadir comparisons between the camera and the Morel&Gentili ModelQnadir comparisons between the camera and the Morel&Gentili Model

1:1

Thank you for your attentionThank you for your attention

Measurements of the in-water radiance fieldMeasurements of the in-water radiance field•History : Univ. Miami, RSMASHistory : Univ. Miami, RSMAS

Ken Voss 1988 –> present : Fish Eye camera coupled with a Ken Voss 1988 –> present : Fish Eye camera coupled with a CID (then a CCD) matrix and spectral filtersCID (then a CCD) matrix and spectral filters

Voss et al, 2007, BiogeosciencesVoss et al, 2007, Biogeosciences


BOUSSOLE-AOPEX cruise, 08/1/2004 BOUSSOLE-AOPEX cruise, 08/1/2004

Measurements of the in-water radiance fieldMeasurements of the in-water radiance field•History :History :

K. Voss 1988 – present : Fish Eye camera with CID (then CCD) K. Voss 1988 – present : Fish Eye camera with CID (then CCD) matrix and wavelength bandpass filtersmatrix and wavelength bandpass filters

Mod

el

Data

Qnadir at 486 nm

K. Voss et al. (2007)


Evolution of the internal temperatureEvolution of the internal temperature


d. antoine, e. leymarie, a. morel, b. gentili laboratoire d'océanographie de villefranche,...

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