GNSS Reflections over Ocean Surfaces

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1 GNSS Reflections over Ocean Surfaces State of the Art F. Soulat CCT Space Reflectometry December 1st 2010 Page n 1

2 Outline Concept GNSS-R Signal On-going Activities ( Applications) CLS GNSS-R Studies CCT Space Reflectometry December 1st 2010 Page n 2

3 GNSS-R R Concept (0/3) transmitter transmitter transmitter transmitter transmitter CCT Space Reflectometry December 1st 2010 Page n 3

4 GNSS-R R Concept (1/3) Def1: GNSS = Global Navigation Satellite System Def2: GNSS-R = a bistatic radar technique using GNSS as sources of opportunity for the monitoring of reflective surfaces, especially the Ocean. Other signals can be considered (e.g., mobile telecommunication) Potential applications: Atmosphere (ionospheric electron content, tropospheric WV) Surface Topography (SSH) Surface Roughness (wind, wave) Surface Dielectric Properties (salinity, pollution, soil moisture, ice) Surface Motion (orbital velocity, large scale currents) Target detection on sea surface CCT Space Reflectometry December 1st 2010 Page n 4

5 GNSS-R R Concept (2/3) Reception Ground, airborne, spaceborne reference Signal characteristics GPS/GALILEO/ Signal Processing Altimetry, Scatterometry, Surface model EM interaction model CCT Space Reflectometry December 1st 2010 Page n 5

6 GNSS-R R Concept (3/3) Winning themes - Coverage, time/space resolution Soon, GPS and Galileo plus augmentation systems (EGNOS/WAAS) will provide more than 50 sources - L-band: Rain immune Potential synergy with existing missions - High quality signals: dual frequency, long-term availability and stability - Inexpensive: passive, off-the-shelf technology Limitations - Low SNR from space - Bandwidth (GPS: C/A 1MHz, P 10MHz) e.g., smaller wrt. RA better performance expected with Galileo CCT Space Reflectometry December 1st 2010 Page n 6

7 GNSS-R R Signals CCT Space Reflectometry December 1st 2010 Page n 7

Waveform Generation Direct GPS signal processing - code despreading (Doppler frequency f 0 corrected) Same processing applied on reflected signal (same Doppler correction) Data Satellite i PRN Code

8 Waveform Generation Direct GPS signal processing - code despreading (Doppler frequency f 0 corrected) Same processing applied on reflected signal (same Doppler correction) Data Satellite i PRN Code Satellite i delay Delay Doppler Map (DDM) built as a series of power waveforms at differents Doppler frequencies (around f 0 ) direct DDM reflected Delay delay Doppler CCT Space Reflectometry December 1st 2010 Page n 8

9 Bistatic Radar Equation Antenna gain Radar function (WAF) 2 G( ) ( t tspec ) sin c WF ( t, f ) c R R ( T f ( )) 2 I p 0 o ( s t r Geometry Scattering ) ds [Zavorotny and Voronovitch, 2000] [Picardi et al., 1998] [Soulat, 2004] Zavorotny, V. U. and A. G. Voronovich, Scattering of GPS Signals from the Ocean with Wind Remote Sensing Application, IEEE Transactions on Geoscience and Remote Sensing, Vol. 38, No. 2, , CCT Space Reflectometry December 1st 2010 Page n 9

10 Waveforms and Applications GNSS-R 2008 Workshop Sept, 2008, ESTEC C. Buck, ESA CCT Space Reflectometry December 1st 2010 Page n 10

11 2D Surface Roughness 1D waveform 2D waveform Low roughness High roughness Reflected Signal (Doppler fo) Specular Point delay Specular Point delay CCT Space Reflectometry December 1st 2010 Page n 11

12 «Glistening Zone» Airborne experiment («Eddy Experiment Flight», Contrat ESA PARIS-Gamma, [Germain et al., 2003]). Integration time: 20 ms, Doppler step: 20 Hz. CCT Space Reflectometry December 1st 2010 Page n 12

13 GNSS-R R Signal Summary GNSS-R signal is characterized by: Reception: antenna (surface weighting by antenna gain) Signal structure: autocorrelation function (iso-delay ellipses) Reception effect: plateform velocity, integration time (iso-doppler hyperbols) Surface effect: roughness ( Glistening Zone ) + 2 strong phenomena: Coherence time e.g., GNSS-R mission 500 km altitude, code C/A : 0.7 ms (nadir) < Tc < 2.3 ms (30 elevation) Impact on integration time v Speckle noise multiplicative noise from scatterers contribrution (I/Q) Impact on incoherent averaging CCT Space Reflectometry December 1st 2010 Page n 13

14 On-Going Activities CCT Space Reflectometry December 1st 2010 Page n 14

GNSS-R R Community Europe Spain: IEEC/C-SIC, UPC, Starlab, University of Valence Germany: DLR, GFZ, Astrium UK: NOCS, University of Surrey, SSTL, Astrium Italy: Univ.

15 GNSS-R R Community Europe Spain: IEEC/C-SIC, UPC, Starlab, University of Valence Germany: DLR, GFZ, Astrium UK: NOCS, University of Surrey, SSTL, Astrium Italy: Univ. Studi del Sannio Sweden: University of Lulea France: CNES, CLS, Ifremer, Telecom Bretagne, ULCO, US NOAA, JPL Boulder University, Purdue University. GNSS-R 10 Workshop, Oct. 2010, UPC, Barcelona GNSS-R workshop every 2 years CCT Space Reflectometry December 1st 2010 Page n 15

16 Spaceborne Altimetry Objective: mesoscale ocean topography measurements Techniques - Eddies monitoring (overall ocean circulation), climate studies,... - Tsunamis detection - [Martin-Neira et al., 1993]: PARIS interferometric system - [Rius et al., 2010]: new concept based on the cross-correlation of direct and reflected signals. Benefit from the full available bandwidth (military signals). Expected precision (~18 cm, including ionospheric, tropospheric, orbital errors, ). Relies on beam forming. ESA PARIS In Orbit Demonstrator: ITTs CCT Space Reflectometry December 1st 2010 Page n 16

17 ESA Altimetric Mission Presentation M. Martin-Neira GNSS-R 10 CCT Space Reflectometry December 1st 2010 Page n 17

18 ESA PARIS IoD Presentation M. Martin-Neira GNSS-R 10 CCT Space Reflectometry December 1st 2010 Page n 18

19 Airborne Altimetry Eddy Experiment, [Ruffini et al., GRL 2004] Starlab Reception from Zeppelin (ZOIS campaigns) GFZ/DLER. Sea-surface height (SSH) over the ellipsoid [m] MSL GPS buoy Jason SSH GNSS-R SSH (average of 3 SVs) CCT Space Reflectometry December 1st 2010 Page n 19

20 Ground Altimetry Several ESA ground experiments - Coastal demonstration of the PARIS system Zeeland Bridge, The Netherlands, 35 m altitude Precision: second (one order of magniture of gain wrt. conventional processing) Phase altimetry - Over calm surfaces (e.g., reservoirs in mountain regions) - Hydrological services developed when accessibility and maintenance not easy (e.g., Starlab) CCT Space Reflectometry December 1st 2010 Page n 20

Phase Altimetry: Example GNSS-R 2008 Workshop 24-25 Sept, 2008,

21 Phase Altimetry: Example GNSS-R 2008 Workshop Sept, 2008, ESTEC GFZ CCT Space Reflectometry December 1st Page n 21

22 Ocean Scatterometry Objective: L-band characterisation of the surface roughness - Wave: Directional Mean Square Slope -Wind Complementary to other missions: - L-band radiometry (SMOS) Data source for L-band sea-roughness in salinity retrieval CCT Space Reflectometry December 1st 2010 Page n 22

23 Spaceborne Reflectometry: CHAMP, SIR-C Few data sets! CHAMP (2000) SIR-C (US spacecraft): 2002 GNSS-R 2008 Workshop Sept, 2008, ESTEC S. Lowe, JPL/Caltech CCT Space Reflectometry December 1st 2010 Page n 23

Spaceborne Reflectometry: UK-DMC Reflection over ice GNSS-R 2008 Workshop 24-25 Sept,

24 Spaceborne Reflectometry: UK-DMC Reflection over ice GNSS-R 2008 Workshop Sept, 2008, ESTEC SSTL Reflection over ocean CCT Space Reflectometry December 1st 2010 Page n 24

Ocean reflected signal Coherent addition of L1B and

25 Spaceborne Reflectometry: Galileo Utilisation de Galileo (Giove-A) Direct signal acquired and tracked Ocean reflected signal Coherent addition of L1B and L1C signals CCT Space Reflectometry December 1st 2010 Page n 25

Airborne Reflectometry: Set-up RHCP LHCP GNSS-R

SONY recorders (20.456 Mbits/s), INS data.

GNSS-R 2008 Workshop 24-25 Sept, 2008, ESTEC

26 Airborne Reflectometry: Set-up RHCP LHCP GNSS-R RHCP/LHCP 3 db antennas, TurboRogue receivers, SONY recorders ( Mbits/s), INS data. 1 min data set 300 MB (dir+ref). GNSS-R 2008 Workshop Sept, 2008, ESTEC Starlab, Eddy Experiment Flight CCT Space Reflectometry December 1st 2010 Page n 26

27 Airborne Reflectometry: Sea Roughness Many flights performed in US [Garrison et al., 2002], - Focus on 1D waveform and wind estimates IEEC/CSIC : GOLD-RTR = GPS Open Loop Differential Real-Time Receiver Starlab : Eddy Experiment [Germain et al., 2003], CCT Space Reflectometry December 1st 2010 Page n 27

28 Coastal Reception: Sea State Estimations of SWH (ex: harbour station, Starlab) CCT Space Reflectometry December 1st Page n 28

29 Occultations Objective: GNSS Radio Occultation (RO) data provide limb sounding of the atmosphere: temperature, pressure, wet component - Because of the signal coherence, the reflected-to-direct delay can be estimated using phase-delay interferometry, a few-cm delay precision. GNSS-R 2010 Workshop Oct, 2010, UPC IEEC Missions - COSMIC RO constellation will be replaced by COSMIC-2 starting in ~2014: 12 satellites equipped with GNSS limboriented antennas, capturing ~8000 RO events every day, globally distributed. - ACES on ISS: primary objective is POD but RO measurements are recorded (A. Helm, Astrium-D) From E. Cardellach, GNSS-R10 Workshop, Barcelona CCT Space Reflectometry December 1st 2010 Page n 29

30 Other Applications Soil Moisture - Many experimental campaigns (cf. Starlab s presentation) - Use of GPS geodesy network (K. Larson, Colorado University): clear signature in interference patterns, pseudo-ranges statistics) Ice - Freeboard - Layers (cf. IEEC s presentation) - Ice age, sea ice extent (scatterometry mode) - Altimetry (low elevation interferometry) CCT Space Reflectometry December 1st 2010 Page n 30

31 CLS GNSS-R R Studies CCT Space Reflectometry December 1st 2010 Page n 31

32 Past Studies ESA PARIS Gamma (in years ) - Impact analysis of the GNSS-R measurements in the altimetric error budget (conventional+gnss-r altimetry) - Consortium: Astrium-UK, IEEC, Starlab, CLS, CNES (2006) - Analysis of the altimetric performances with GNSS-R (2006) Theoretical SNR and link with the precision in delay Mission scenario analysis - Consortium: Starlab, CLS Radar Division (BOOST-Technologies) CCT Space Reflectometry December 1st 2010 Page n 32

Recent Study GNSSDETEC: Ship Detection (2010) - Maritime security

for validation and in support to existing

, AIS) - Feasibility study and simulations: SNR Measurements density

33 Recent Study GNSSDETEC: Ship Detection (2010) - Maritime security context Cost-effective system to provide complementary information for validation and in support to existing systems (e.g., AIS) - Feasibility study and simulations: SNR Measurements density Detection algorithm (DDM Bistatic SAR processing target detection) - Consortium: CLS, Télécom Bretagne CCT Space Reflectometry December 1st 2010 Page n 33

34 Thank you for your attention CCT Space Reflectometry December 1st 2010 Page n 34

The Typhoon Investigation using GNSS-R Interferometric Signals (TIGRIS)

The Typhoon Investigation using GNSS-R Interferometric Signals (TIGRIS) F. Fabra 1, W. Li 2, M. Martín-Neira 3, S. Oliveras 1, A. Rius 1, W. Yang 2, D. Yang 2 and Estel Cardellach 1 1 Institute of Space