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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