Simulations and exploitation of GNSS-R signals from a 60-meter lighthouse for applications in...

Simulations and exploitation of GNSS-R signals from a 60-meter lighthouse for

applications in surface hydrology processes

Space Reflecto 2013

Nicolas ROUSSELLaurent LESTARQUIT

PhD advisers: Guillaume RAMILLIEN, Frédéric FRAPPART

04/05 novembre 2013

2

PlanIntroduction Simulations Field measurements

Introduction

Simulations

Field measurements

GNSS-based tide gauge system with SILICOM datalogger

Analysis of signal-to-noise ratio (SNR) series

4/5 November 2013 Space Reflecto – Nicolas ROUSSEL / Laurent LESTARQUIT


Introduction

Simulations

Field measurements




Ground configuration Embedded configuration

Direct/reflected signals correlation

Position of the specular reflection point Altimetry Properties of the reflection surface

(roughness)

Source : Institut de Ciències de l’Espai (http://www.ice.csic.es)

IntroductionIntroduction Simulations Field measurements


- 60

m -

IntroductionIntroduction Simulations Field measurements

The Cordouan Lighthouse (45°35’11’’N ; 1°10’24’’O)



Introduction

Simulations

Field measurements




Modeling the trajectories of GNSS electromagnetic waves that are reflected on the surface of the Earth, based on real ephemeris

Determine the potential of GNSS-R for mapping the characteristics of the reflecting surface

Explore different configurations of performing measurements and instrument installations:

variations in the reflectometer height, mask effects due to the terrain, satellites geometry, ...

Simulator development

SimulationsIntroduction Simulations Field measurements



Determination of the position of the specular reflection points: 3 algorithms

- Approximation of the Earth into a local sphere

- Approximation of the Earth into a local ellipsoid

- DEM (Digital Elevation Model) integration

CorrectnessComputation

speed

Gnu R

For further information : Simulations of direct and reflected waves trajectories for in situ GNSS-R experiments, submitted in Geosciences Model DevelopmentN. Roussel, F. Frappart, G. Ramillien, C. Desjardins, P. Gegout, F. Pérosanz, R. Biancale


Simulator outputs Simulations on the Cordouan lighthouse (45°35’11’’N ; 1°10’24’’O)



Simulations over a week



Introduction

Simulations

Field measurements





14


Introduction

Simulations

Field measurements




SILICOM Data-Logger

Data Logger

records and time tags a wide choice of supported RF GNSS signals

makes possible the characterization of the reflected signal and the development of algorithms for processing the GNSS-R signals.

SILICOM Data-loggerIntroduction Simulations Field measurements


31st may 2013 campaign

Data Logger

to collect GNSS-R signals, receiving the direct signal via a RHCP zenith-looking antenna, and the reflected signal via a LHCP nadir-looking antenna

Approx. 25 min of acquisitions, 25 MHz, 8 bits



Acquisition

1 ms Doppler : [-5000:1:5000] Hz

Detection of 6 satellites :

- PRN12- PRN15- PRN17- PRN24- PRN25- PRN26

In agreement with the simulations



Acquisition

Reflected signalDirect signal

PRN15 exemple : detection of the initial doppler



Acquisition


PRN15 exemple : detection of the initial delay



Correlation functionReflected signalDirect signal


1 ms 1 ms

100 ms100 ms


Correlation function



1 ms 1 ms

100 ms100 ms


Delay-Doppler Maps



Tracking



Differences between direct and reflected paths – C/A PRN12

Time (s)

Dis

tanc

e (m

)

𝛿d=2h𝑠𝑖𝑛(𝜖) : satellite elevation

Determination of the C/A pseudo-distance for both direct and reflected signals The difference between both gives the extra distance traveled by the reflected wave

Tracking

Direct signal

𝛿d=2h𝑠𝑖𝑛(ϵ ) With the elevation Satellite Num Receiver height h (m)

PRN12 57,47

PRN15 60,47

PRN17 57,75

PRN24 61,98

PRN25 61,66

PRN26 59,46

Mean 59,80 ± 1,92



25


Introduction

Simulations

Field measurements




26


Introduction

Simulations

Field measurements




phase difference between the direct signal and the reflected signal (multipath)

Direct signal amplitude

Multipath amplitude

x = sin θ :

SNR dataIntroduction Simulations Field measurements

Larson et al., GPS Sol., 2008



L2 SNR data

2nd order polynom




L2 SNR data

0 – 40° elevation filtration


L2 SNR data


The whole 3 months time series is currently being analyzed in order to make the tide appear

Thanks for your attention !

Simulations and exploitation of GNSS-R signals from a 60-meter lighthouse for applications in...

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