CNES activities in LEO DTE

G. Artaud, J-L. Issler

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"OLEODL-Workshop" at DLR-IKN on 10th Nov. 2016

LEO DTE SCENARIO

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� « Low complexity » scenario: � up to 10Gbps � Target: nanosat and microsat� Simple implementation: amplitude modulation, receiver with APD

� « High data rate » scenario:� High throughput 10 to 100Gbps� Target: very high demanding earth observation satellites� Provide more throughput than RF � More complex architecture

Atmospheric effects on optical links

FSO links significantly impaired by atmospheric effects:

� Atmospheric absorption & clouds/aerosol attenuation» Study and PhD on that subject» Goal is to obtain variability of absorption in function of elevation

cause by semi transparent clouds and various aerosols

� At large scale: Clouds» Availability increased through site diversity» Ground network optimized using cloudiness experimental datasets

� At small scale: Atmospheric turbulence» Provision in link and pointing budgets, mitigation through air interface» Assessment and optimization using the TURANDOT simulator» Turbulence measurement on stars and satellite laser link» mitigation technique: Adaptive Optics

Turbulence

Ground Network planification Tool

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� Developped with meteo France� Use of SATMOS data (MSG)� Cloud type every 15mn, pixel 4km x 4km� Europe and north Africa

� GEO and LEO� Genetic algorithm� select the best N locations

� Example with GEO satellite, Europe area, 3 years of data :

Cloud typemean cloud coverage

using surounding pixels

Nb Stations Availability

3 95.859

4 97.845

5 98.818

7 99.435

10 99.788

Turbulences

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� Simulation tool: TURANDOT� From PILOT scientific software developed at ONERA/DOTA (“wave optics”)� engineering tool for turbulence simulation (main output: Far Field Patterns)

� Experimental measurements

Free atmosphere

Boundary layer

HV 5/7

Provided by ONERA: DOTA-SIMCOP-NTE-0004

Emission/ reception scenario study

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� For a given propagation channel and link budget at 20°� Comparison of architectures:� OOK – receiver APD; Rx telescope 50cm� OOK – receiver single mode preamplifier + PIN (using AO) ; Rx telescope 25cm� DPSK - receiver single mode preamplifier + PIN (using AO) ; Rx telescope 25cm

� received power from simulations (link budget, propagation, AO, SMF coupling, EDFA,…)� BER curves in function of received power� Statistics on fading duration and interfading time

Received power

Coupled in SMF

Example of fadding statistics on 4sec with preamplified RZ-DPSK

From ALOES study conducted by ADS, TAS and ONERA

Physical layer study

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� Development of a simulator :� Simulate optical emission and reception � apply propagation time series� Evaluate FEC using mutual information theory� Test interlievers

� PhD : study of balance between OA , interleavers, FEC at physical layer and FEC at higher layer

L. Canuet, N. Védrenne, J-M Conan, G. Artaud, A. Rissons, and J. Lacan, “EVALUATION OF COMMUNICATION PERFORMANCE FOR ADAPTIVE

OPTICS CORRECTED GEO-TO-GROUND LASER LINKS”, ICSO2016

10W amplifier prototype

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� Developement of a prototype of a 10W optical amplifier in C band� Conducted by CILAS and IXBLUE� Space environment qualification tests (radiation, vibrations, thermal cycling, …)� Defined for data transmission and for fondamental science� Planning� CDR: 12/2016� End of functional tests: 01/2018� End of qualification: 10/2018

� Specifications:� Wavelength: range 1545 nm - 1565 nm� Input power: ∼10 mW� Output power : ≥10 W � Noise factor : ≤ 7 dB� Gain flatness in the band 1545 nm – 1565 nm : ≤1dB� Polarisation : PER > 20dB� Single mode: gaussian beam� Efficiency: ≥ 12%� Life time: 10 years

Optical telecommunication demonstration between �SOTA optical terminal onboard SOCRATES microsatellite�MeO Optical Ground Station at OCA

Objectives�Study of Propagation channel�Link budget�Design of an OGS

Collaboration�NICT�CNES�OCA�ONERA�ADS &TAS�New: NASA with OPALS

DOMINO ProjectDemonstrator for direct Optical transMission at hIgh data rate iN Orbit

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DOMINOOGS Architecture

Downlink

Receiver Bench

TF Labo Focus LaboratoryControl

Dome

Tra

nsm

itte

r

Optical Turbulence Monitoring

ODISSEE

WFS

M4

NTP

Serveur

H-Maser

1.54 m

Telescope

Re

ceiv

er

195 mm

Telescope

Laser

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Downlink

Receiver Bench

TF Labo Focus LaboratoryControl

Dome

Tra

nsm

itte

r

Optical Turbulence Monitoring

ODISSEE

WFS

M4

NTP

Serveur

H-Maser

1.54 m

Telescope

Re

ceiv

er

195 mm

Telescope

Laser

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DOMINO OGS Architecture1550nm Nasmyth

DOMINO OGS Architecture976nm ODISSEE

Downlink

Receiver Bench

TF Labo Focus LaboratoryControl

Dome

Tra

nsm

itte

r

Optical Turbulence Monitoring

ODISSEE

WFS

M450%/50%

NTP

Serveur

H-Maser

1.54 m

Telescope

Re

ceiv

er

195 mm

Telescope

Laser

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Nasmyth bench anduplink 195 mm Telescope

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Power fluctuation

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47 sec (21.0°->28,8°)

1549 nm laser

171 sec (11,6°->45,4°)

172 sec (9,2°->34,5°)

976 nm laser

253 sec (6,2°->48,8°)

90 sec (35°->65,5°)

Atmospheric Turbulence Analysis using ODISSEE AO bench

• Took opportunity of already existing AO bench• AO bench working on telescope full pupil

(1.5 m ! 25<D/ r0 <36 @500nm)

• AO bench not designed for telecommunication applications(satellite imaging, concepts/components validation)

Wavefront sensor: E2V EMCCD220 OCAM² Firstlight Imaging8x8 square subaperturesShannon/2 sampling @ 600 nm1500 Hz

PCO imaging camera (100Hz)

10x10 piezo

stacked deformable

mirror (CILAS)

10kHz bandwidth

TT mirror

Control:

- 1.45kHz sampling frequency,

- 3.3 frame delay

- Straightforward WFS slopes

computation and DM control

SH-WFS data analysis and propagation channel caracterisation

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Measurement of the turbulent parameters during the pass ( 21 July)

Fried Parameter Scintillation index

Turbulence profile estimation based on WFS slopes and intensities

AO results: AO correction

Without AO with AO

short exposure images (each normalized to 1)Without AO with AO

?

(each normalized to 1)

Long exposure images (same scale)

Without AO with AO

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Preliminary results of coupling into a SMF (SOTA, 10/21/2015)K. Saab Phd Thesis

Close loop (SOTA)

Simultaneous acquisition of PSF and output of SMF to consolidate injection efficiency models

Close loop (SOTA)Open loop (SOTA) Internal close loop PSF

• Open loop: pointing residual => PSF out of FOV

• Close loop: injection into SMF

Theoretical coupling efficiency : 4,1 %, measured: 2,1%

Poor coupling efficiency: turbulence residuals (r0 ~ 7 cm @ 976 nm)

To improve the coupling efficiency the Telescope diameter shall be reduced

LISA AO bench at 1550 nm 40 cm pupil Nasmyth

• A new small adaptive optics bench (30 x 60 cm wide) has been developed and integrated by ONERA, at the nasmyth of MeO

• As for ODISSEE, the usefull aperture at the telescope level has been reduced to 40 cm to be representative of laser communication systems.

• The wave front sensor runs at 2.2kHz and the deformable mirror has 97 actuators.

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CONCLUSION

• Overview of CNES activities in the domain of LEO DTE

• Field measurements are needed in order to improve our knowledge onFree space optical communications between space and Earth

• The few links that have been successfully established with SOTAprovide valuable insight on link budget and the contributions ofpointing and atmospheric turbulences

• Having access to a laser link from a satellite enables to assessperformances of techniques such as adaptive optics in the conditionsof the future system

• More experimental links need to be performed in order to obtain morevariability on the transmission conditions and be finally able to sizefuture operational laser communication systems for space to ground

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