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1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger , Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David P. Cotton (Satellite Oceanographic Consultants) R. Keith Raney (Johns Hopkins Uni/Applied Physics Lab) Jérôme Benveniste (ESA/ESRIN)
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1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

Apr 01, 2015

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Page 1: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

1

SAR Altimetry numerical simulations over water surfaces

Christine Gommenginger, Paolo Cipollini (NOCS)

Cristina Martin-Puig, Jose Marquez (Starlab)

David P. Cotton (Satellite Oceanographic Consultants)

R. Keith Raney (Johns Hopkins Uni/Applied Physics Lab)

Jérôme Benveniste (ESA/ESRIN)

Page 2: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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Presentation Content

• What is Delay-Doppler Altimetry (DDA)?

• The ESA SAMOSA project

• Motivation and methodology

• CRYMPS DDA simulations over water

• First results

• Conclusions

Page 3: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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What is Delay-Doppler Altimetry (SAR) ?

Page 4: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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Conventional ALT footprint scan

Vs/c) ) ) ) ) )

RA pulse-limited footprint in effect is dragged along the

surface pulse by pulse as the satellite passes

overhead

RA pulse-limited footprint in effect is dragged along the

surface pulse by pulse as the satellite passes

overhead

)

Courtesy: K.Raney

Page 5: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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DDA: a fundamentally different method

Vs/c

DDA spotlights each along-track resolved

footprint as the satellite passes overhead

DDA spotlights each along-track resolved

footprint as the satellite passes overhead

) ) ) ) ) ) )

Courtesy: K.Raney

Improved along-track resolution, higher PRF, better S/N, less sensitivity to sea state,…

Page 6: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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ESA SAMOSA project

• SAMOSA - Development of SAR Altimetry Mode Studies and Applications over Ocean, Coastal Zones and Inland Water

• Project management: David Cotton, SatOC• Consortium members: NOCS, Starlab, De Montfort University,

Danish National Space Centre• Tasks:

1. Review state of the art (Starlab)2. Quantify improved range error in different sea states (NOCS)3. Assess recovery of short scale surface slope signals (DNSC)4. Develop theoretical model for DDA waveforms (Starlab)5. Assess capability in coastal zone and inland waters (DMU)6. Application to RA-2 individual echoes (NOCS)7. Validation with ASIRAS data (DNSC)

Page 7: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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Motivation• Task 2: to independently validate Jensen & Raney

(1998) on improved sea level retrieval with DDA against sea state

Page 8: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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Methodology

• CRYMPS: Cryosat Mission Performance Simulator• CRYMPS developed & run at University College

London/MSSL, in collaboration with ESA/ESTEC• Simulates the CryoSat platform orbit and

instrument operation, generates official Cryosat products for LRM, SAR and SARIn mode, for a given (explicit) surface

• Simulator and surface descriptors optimised for ice/sea ice surfaces

• Here, CRYMPS is applied to ocean surfaces

Page 9: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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Code Description SWH Swell Amplitude

Swell wavelength

PDF s.d.

F13 F1: CRYOVEX 2006, 02/05/2006

F3: CRYOVEX 2006, 30/04/2006

1.41m

0.71m

1.0 m

0.5 m

100 m

50 m

4 cm

4 cm

F24 F2: moderate sea state

F4: high sea state

4.23 m

14.1 m

3.0 m

10 m

150 m

200 m

10 cm

10 cm

C3 Realistic ocean wave spectrum (Elfouhaily et al., 1997)

1/2/3 m N/A N/A 10 cm

C1 Realistic ocean wave spectrum (Elfouhaily et al., 1997)

0.1/4/5 m N/A N/A 10 cm

FT1 Sea Floor Topography 1, variations in sea surface height, low swh, short wavelength

1.41 m 1.0 m 100 m 4 cm

CRYMPS runs over open ocean

Page 10: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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Example: C3 scenarioC3

+3m

-3m

Hs = 1m Hs = 2m Hs = 3m

Page 11: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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Example: C1 scenarioC1

+5m

-5m

Hs = 0.1m Hs = 4m Hs = 5m

Page 12: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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CRYMPS SAR 18kHz

Pseudo-LRM 20Hz

CRYMPS LRM 20Hz

NOCS ocean waveform retracker (Brown model)

Ocean surface DEM

CRYMPS

SAR->LRM Reduction (Starlab)

Page 13: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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64 pulses per burst

etc

etcLRM mode

SAR mode

PRF: 1970 Hz

Continuous

Burst period 11.7 ms

Generation of Pseudo-LRM Waveforms from SAR-mode: Revised (1/4)Extrapolate from the original pre-sum model

time

time

PRF: 17.8 KHz

within bursts

SAR -> pseudo-LRM reduction ?

. . .

Extract 1 in every 9 waveforms

We get 8 waveforms per burst:Wf1+wf10+wf19+wf28+wf37+wf46+wf55+wf64

9SAR

LRM

PRFn

PRF= =

Courtesy: K.Raney & C. Martin-PuigWork in Progress !

Page 14: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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20Hz pseudo-LRM

. . .

SAR

t

PRFSAR = 17.8KHz

Apply IFFT0Apply IFFT0

|.|^2|.|^2

20Hz rate Incoherent averaging20Hz rate Incoherent averaging

RDSAR

I,QI,Q

Page 15: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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First results

Page 16: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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C3 LRM Hs: 0.145m

• 16 seconds along-track• 260 LRM samples along-track

• No Power Scaling applied– No along-track variability in

peak amplitude– No Sigma0 info

• Amplitude scaled by 10-6

Page 17: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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C3 RDSAR Hs: 0.145m

• 16 seconds scenarios • 250 samples along-track

• No Power Scaling applied

Page 18: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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Ocean retracker results

C3 LRM

Page 19: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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Ocean retracker results

C3 RDSAR

Page 20: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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Conclusions

• SAMOSA will assess the improved performance of DDA w.r.t. pulse-limited altimetry to:– Retrieve higher-accuracy ocean range, detect short-scale surface

slope, extend altimetry to the coastal zone,…

• Methodology is based on Cryosat-type SAR and LRM data from the CRYMPS simulator applied to ocean surfaces

• Reduction of SAR -> pseudo-LRM still debated• First results show that:

– CRYMPS produces realistic LRM and DDA waveforms– the CRYMPS waveforms were successfully retracked with the

NOCS ocean retracker, both LRM and RDSAR

Page 21: 1 SAR Altimetry numerical simulations over water surfaces Christine Gommenginger, Paolo Cipollini (NOCS) Cristina Martin-Puig, Jose Marquez (Starlab) David.

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SAR Altimetry numerical simulations over water surfaces

Thank You !

For further info, contact Christine Gommenginger

[email protected]