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Optical Communication Experiment using Very Small Optical transmitter with SLR station
National Institute of Information and Communications Technology, Japan Space Communications System Laboratory Hiroo Kunimori and VSOTA TEAM
Sep 24, 2012 WPLTN Technical Workshop@St.Petersburg, Russia


Table of Contents


Backgound:HODOYOSHI Project
JapaneseHODOYOHI= Reasonable Reliability Engineering to develop series of 50kg Satellite. Project initiated by Prof. Nakasuga, Tokyo Univ. in 2009 Sub-Theme: LEO-GEO-GND High bandwidth Optical Communication Technology Tohoku Univ. and NICT collaboration work on No.2 satellite of the project called RISESAT Optical Communication High Date rate with small resources No license needed Highly accurate pointing control needed Poor availability to GND depending on weather condition Best means for satellite-satellite Communication However, Direct link to GND the first step and possible mitigation by site diversity Tohoku Univ. RISESAT Project 2012
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Motivation: Site diversity ­Views in the futureSLR stations as down link sites in the world,

J.Degnan, IWLR, SanFernando, Spain,2004

Synergy of two applications


We SLRs know and capable of:
· Telescope and gimbal accurate enough to ATP to the communication satellite. · How to share wavelength communication beam and ranging beams. · (Too) accurate time and frequency source and reference frame to do optical communication. · Providing communication satellite with beacon at the same time of ranging and/or Communication satellite provided beacon as Adaptic Optics point source to stabilize communication channel.


Recent Example of Laser Comm. Development using SLR station: UPLINK using kHz Laser
G.Kirchner, 17th ­IWLR Bad Koetzting, Germany, 2011


Experience of Optical Communication OICETS 2006-2009 by NICT/JAXA
· Total of 50 Experiment 37% Successful tracking passes with a maximum duration about 6 minutes · Footprint of the laser beam: only ~6 m (distance 1000 km)
Downlink laser beam Uplink laser beam Wavelength 800nm/850nm

El = 33 deg (max)

CCR is located at opposite side of telescope
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What is VSOTA ?
· VSOTA=Very Small Optical Transmitter for component validation MOTIVATION: Opportunity of space validation on our road map. A simple light-weight space optical communication terminal using parts for SOTA(Small Optical Transponder) components which NICT has been developed for years. The experiment using optical ground station heritage of experience of OICETS in which the same telescope used by SLR. Launch : Scheduled in Fiscal 2013.
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VSOTA Experiment overview
Onboard Laser Component NICT RISESAT Satellite

BODY POINTING (Tohoku University)

Optical Down link experiment

NICT 1.5m/1m Telescope

NICT 35cm Telescope

Mobile e.g.20cm Telescope

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VSOTA Component look-out
Cube Mirror for Alignment to satellite reference 1550nm 980nm

Collimator(VSOTA-COL) Optical Fiber No gimbal and Fine Pointing Mirror LD DriverVSOTA-E)

Corner Cube RetroreflectorVSOTA-RR)

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dual LD Specification
1. Optical Source
a) b) c) d) e) Wavelength 980nmnominal) Power 270mW(nominal) Modulation speed : 10Mbps (max) OOK Beam Div. 3.5mrad Polarization arbitrary 1550nmnominal) Wavelength Power 40mW(nominal) Modulation speed 10Mbps (max) OOK Beam Div. 1.3mrad Polarization Linear
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2. Optical Source 4
a) b) c) d) e)


CCR Design Parameters
Number of Cubes: 1 Material : Quarts Cube diameter: CA 28mm Reflectivity>98%@532nm Dihedral angle = 2.4 arcseconds +-0.4 Structure material: Main material:A7075-T351 Surface finish by Alodine Retainers: BESPEL SP-1 Others: 28mm Ring SUS304CSP/4H Weight: 40g
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SLR and Communication Beam

Passive sensor CCR and HPT CCD sensor

Nominal SLR 532nm 35ps 20Hz 1W Divergence and ND filter control set by orbit prediction accuracy and sensitivity of HPT sensor RISESAT/VSOTA Downlink 980nm/1550nm

Fixed station Mobile stations
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HPTHigh Precision Telescope) to evaluate satellite attitude developed by Hok
Univ.

kaido

Remote sensing and astronomical science Aperture 10cm Cassegrain form Primary mirror made of Zero thermal expansion Pore-Free ceramics (ZPF) In front of CCD with Liquid crystal Tunable spectral filter (LCTF)

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VSOTA satellite interface
Mass Total Satellite Mass 55kg VSOTA: 700g Orbit700-800km Polar orbit

Power consumption 3.5W( 10 minutesnight nominal max allocated power 15W including heater Body Pointing Accuracy 0.1degree or 1.7mrad3Requirement 0.04 degree or 0.7mrad 3 Goal Space Environment test condition defined by each rocket interface
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Link analysis
Altitude800km Pointing Accuracy0.1 deg 3 Best case High elevation and good atmospheric condition Worst case: Low elevation and add large atmospheric turbulence Aperture size1.5m,1m 35cm, 20 cm
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Link Analysis(Best case @980nm

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Link Analysis (~worst case)
1.5m Telescope EL=23deg Atmospheric turbulence -23dB)

Received power Min. Sensitivity Margin

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Margin and BER
Yellow Bar stands for best case 980nm channel for Each telescope Diameter Red Shows when worst case (low elevation etc.)

Intensity Modulation Direct Detection NRZ

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0

10

0

20cm

35cm

1m,1.5m

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-1

BER

1 BER = er 2

SNR fc 22

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-2

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-3

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-3

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-4

10

-5

10

-6

10

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0

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4

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SNR

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Experiment plan
Minimum · success

· · ·
Normal Success

· · ·

Maximum Success

SLR to confirm orbit prediction and monitor ATP process to perform communication experiment. Turn on VSOTA Both LD status OK on telemetry Optical Tracking successful 980nm by ground telescope i.e. visible bright spot on tracking camera centering. Photo diode record on both wavelength (980nm&1550nm) for atmospheric turbulence research PN code receive to evaluate BER at any transmitting rate Transmit a mission data(Advanced ­ GPS data/Mission data download ­ Adaptive optics experiment
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Thank you


Capability of Receive Sensor
Wavelength N EP Sensitivity Bandwidth Minimum Noise Circuit Noise Quantum Efficiency Minimum sensitivity
980nm 0.02E-12 13E-12 100k -83 0 -3 -80 1550nm 3.0E-14 100k -108 -28 -0 -78

980nm APD C5460-01 NEP = 0.02E-12 W/Hz1 Sensitivity13E-12 W/Hz1/2 1550nm PD G8605-15 NEP = 3E-14 W/Hz1/2

/2

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SOTA: Small Optical TrAnsponder
Major design parameters of the PFM Mass Power Link range Wavelength Data Rate 6.2 kg 40W 1000km -2000 980nm,1540nm,(TX) 800nm(TX) 1064nm(RX) 10Mbps

Electric Part

Optical on Gimbal Mechanics
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LD and driver board and Collimator VSOTA Compoonent


Z Panel
VSOTA-COL

DOTCAM

HPT
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Case: Altitude

Visibility of Satellite
UTC

Observation Time max 15 min

2014 April 1-5 South to North Pass at Night