The Typhoon Investigation using GNSS-R Interferometric ......Experimental campaign in Shenzhen (China) Preliminary results Conclusions The Typhoon Investigation using GNSS-R Interferometric

IntroductionExperimental campaign in Shenzhen (China)

Preliminary resultsConclusions

The Typhoon Investigation using GNSS-RInterferometric Signals (TIGRIS)

F. Fabra1, W. Li2, M. Mart́ın-Neira3, S. Oliveras1, A. Rius1,W. Yang2, D. Yang2 and Estel Cardellach1

1Institute of Space Sciences ICE-CSIC/IEEC, Spain2School of Electronic and Information Engineering SEI, BeiHang University, China

3European Space Agency ESA-ESTEC, Netherlands

SPACE REFLECTO 20133rd Conf. on passive reflectometry using radiocom space signals

Fran Fabra, ICE-CSIC/IEEC SPACE REFLECTO. Nov 5th, 2013. Brest (France).



Outline

1 Introduction

2 Experimental campaign in Shenzhen (China)

3 Preliminary results

4 Conclusions




FrameTyphoon remote sensing

Outline

1 Introduction



4 Conclusions





The frame of this work

China-Europe Joint Initiative

National Remote Sensing Center of China (NRSCC), Ministry of Science andTechnology

School of Electronic and Information Engineering (SEI), BeiHang University

China Meteorological Administration (CMA)

European Space Agency (ESA)

Institute of Space Studies from Catalonia (IEEC)

+ Other institutions

TIGRIS experiment

Typhoon Investigation using GNSS-R Interferometric Signals

Main purpose: Research on GNSS-R towards remote sensing of typhoons

But also: Provide recommendations for a future GNSS-R space-based mission

Related work: aircraft experiments done by S.J. Katzberg and NASA’s CYGNSSmission





Typhoon remote sensing with GNSS-R

Basic idea...

Typhoons can be characterized by itsimpact over the sea surface

Remote sensing measurementsthrough intense rain fall (lowerattenuation at L-band) ⇒ betterunderstanding on typhoon’s air-seainteraction

Potential retrievals

Wind Speed (WS) ⇒ waveform’samplitude and area

Significant Wave Height (SWH) ⇒waveform’s leading edge andcoherence time

Sea Surface Level (SSL) anomalies(up to 1 m) ⇒ altimetry

Interferometric waveforms (all GPS codes) with different wind

speeds simulated by W. Li under PARIS IoD nadir geometry




ScenarioInstrumentationCollected data

Outline

1 Introduction



4 Conclusions





Location: Xichong bay, South-East of China





Scenario: Antennas installation in Shenzhen site





Campaign: Instrumental setup

Antenna Inputs

RF Coaxial

N−Type Female

PS1234

IN

PSIN

12

PSIN

12

PSIN

12

Up−looking Low−gain Antenna

Up−looking High−gain Antenna

Down−looking High−gain Antenna

ANTENNA SYMBOLS

Nav

EthUSBPower

GOLD−RTR

Power

Eth

RF1

RF0

Power Supply Jack

PIRA

PSIn

12

IEEC’s Equipment

Link−3

Link−2

Link−1

Nav

Power Input

CEE 7/7 plug

AC 220V/50Hz

SEI’s Equipment

USB

USB

IN1

IN2

IN3

IN1

IN2

4−channel GPS IF signal collector

2−channel BeiDou IF signal collector

A4) RHCPA3) LHCP

A1) RHCP A2) RHCP

IN4

RHCP−U−H

RHCP−U−H

LHCP−D−H

LHCP−D−H

RHCP−D−H

RHCP−U−L

LHCP−D−H

LHCP−D−H

RHCP−U−L

RHCP−D−H

POWER SPLITTER (PS)

2, 3, 4 Outputs DC BLOCKED

IN Input DC THRU

1 Output DC THRUIEEC: Institut d’Estudis Espacials de Catalunya

SEI: School of Electronic and Information Engineering

INSTITUTIONS





Campaign: IEEC’s GNSS-R Instrumentation

GOLD-RTR

GPS Open Loop Differential Real Time Receiver

GNSS-R dedicated hardware receiver (standard approach using GPS L1 C/Acode)

10 channels compute cross-correlations (waveforms) of 64 lags every millisecond

50 ns lagspacing ⇒∼ 15 meters

PIR

PARIS Interferometric Receiver

GNSS-R dedicated hardware receiver (direct cross-correlation)

1 waveform of 320 lags every millisecond

12.5 ns lagspacing ⇒∼ 3.75 meters





Campaign: SEI’s GNSS-R Instrumentation

BeiDou IF signal collector

Dual-front-end for both direct and reflected signals

16.367 MHz sampling rate (18.75 meters resolution in delay)

Configurable to BeiDou, GPS and GALILEO

GPS IF signal collector

Quad-front-end channels

16.3667 MHz sampling rate

GNSS-R software receiver in post-processing

Computes waveforms using standard or interferometric approaches

Compatible with both Beidou B1 and GPS L1 band signals





Collected data during typhoons

Relevant aspects

Campaign’s duration: from end of July until end of September 2013

Two typhoons and one tropical storm were monitored!

An additional (but simpler) setup collected data from Yangjiang station

Name Classification Min. pressure Dates DistanceJEBI Strong Tropical Storm 985 mbar 31-July/3-Aug 470 km

UTOR Super Typhoon (cat. 4) 925 mbar 9-Aug/15-Aug 270 kmUSAGI Super Typhoon (cat. 5) 910 mbar 16-Sept/23-Sept 100 km

Preliminary results given next

Altimetric retrievals from GOLD-RTR around UTOR and USAGI

Scatterometric measurements from BeiDou IF signal collector around JEBI andUTOR




Altimetric resultsScatterometric results

Outline

1 Introduction



4 Conclusions





Altimetric results

Main aspects

Results from IEEC’s GOLD-RTR

High gain antennas should avoiddirect signal contamination

However, we try to removewaveforms with presence ofresidual direct signal

Estimated coherence time of100 msec ⇒ 100 sec ofincoherent integration tominimize speckle (120 sec forpractical purposes)

Two periods analyzed: aroundUTOR and USAGI

245.44˚W 245.43˚W 22.47˚N

22.48˚N

5.00

10.00

15.00

20.00

25.00

30.00

Ele

vatio

n [

de

g]

Specular points over the ocean surface from

GPS tracks during 14th Aug





Altimetric results: specular delay

Main aspects

Position of waveform’s peakpower (instead of maximum offirst derivative)

Related to altimetry

Low elevation angles magnifyaltimetric errors duringdelay-height inversion

Only values obtained forelevations > 25◦ are considered

20

40

60

80

100

120

Alti

metr

ic d

ela

y [m

]

5 10 15 20 25 30

Elevation [deg]

2 H sin(elevation)

−40

−20

0

20

He

igh

t re

sid

ua

l [m

]

5 10 15 20 25 30

Elevation [deg]





Altimetric results: specular delay

−2.0

−1.5

−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

Est

ima

ted

SS

L [m

]

00 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 00August 13 August 14 August 15 August 16 August 17 August 18

UTOR’s landfall

−2.0

−1.5

−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

Est

ima

ted

SS

L [m

]

00 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 00 06 12 18 00September 18 September 19 September 20 September 21 September 22 September 23

USAGI’s landfall





Altimetric results: specular delay (OSU Tide model)

−2.0

−1.5

−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

Est

ima

ted

SS

L [m

]


UTOR’s landfall

−2.0

−1.5

−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

Est

ima

ted

SS

L [m

]


USAGI’s landfall





Altimetric results: specular delay (tide-corrected)

−2.0

−1.5

−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

Est

ima

ted

SS

L [m

]


UTOR’s landfall

−2.0

−1.5

−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

Est

ima

ted

SS

L [m

]


USAGI’s landfall





Altimetric results: Discussion

First impressions

Altimetric retrievals showmoderate agreement with tides,but errors are larger thanexpected

Altimetric errors showtrack-evolution ⇒ multipatheffect due to direct signalcontamination!

Next step: to retrieve altimetryfrom more robust phaseobservables (experience fromprevious campaigns)

−2

−2

−1

−0

0

0

1

2

2

Est

ima

ted

SS

L [m

]

00 06 12 18 00August 14

5

10

15

20

25

30

Ele

vatio

n [d

eg

]

−30

−25

−20

−15

−10

−5

0

5

10

Est

ima

ted

SS

L [m

]

00 06 12 18 00August 14

5

10

15

20

25

30

Ele

vatio

n [d

eg

]





Scatterometric results

Main aspects

Results from SEI’s BeiDou IFsignal collector

BeiDou GEO #1 and #4satellites are monitored ⇒ stablegeometry and sharperauto-correlation function (2.046Mchips)

Off-specular reflections ⇒spatial filtering of antennafootprint and coastline

Two observables are analyzed:Area of the waveform andcoherence time

Two periods processed: aroundJEBI and UTOR

Specular points from BeiDou GEO #1 and #4

satellites





Altimetric results: Area of the power waveform (JEBI)

Area of the power waveform

Expected to be sensitive to the sea surface wind

speeds (proportional)















Expected to be sensitive to the sea surface wind speeds (proportional)





Altimetric results: Area of the power waveform (UTOR)








Altimetric results: Coherence time (JEBI)

Coherence time

Expected to be sensitive to the Significant Wave Height (inversely proportional)





Altimetric results: Coherence time (JEBI)

Coherence time






Altimetric results: Coherence time (UTOR)

Coherence time






Altimetric results: Coherence time (UTOR)

Coherence time





Outline

1 Introduction



4 Conclusions




Conclusions

Altimetric results

Moderate agreement with tides, but errors are larger than expected due todirect signal contamination

Preliminary results still have room for improvement!

More robust phase observables might overcome these limitations

Scatterometric results

Good correlation with the in-situ wind speed and SWH measurements

Off-specular reflections (spatial filtering of antenna footprint and coastline)benefit coastal applications

BeiDou GEO satellites provide good opportunities for sea state measurement

On-going analysis

Phase-based and polarimetric measurements, GPS interferometric signals...

Combined analysis is required to enable a proper typhoon characterization




Thank you for your attention


Documents

The Typhoon Investigation using GNSS-R Interferometric ......Experimental campaign in Shenzhen (China) Preliminary results Conclusions The Typhoon Investigation using GNSS-R Interferometric