10/25/2011

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GEOSYNCHRONOUS

TELECOMMUNICATION

SPACECRAFT DESIGN

D.J.P. Moura

SYSTEM REQUIREMENT

SPACECRAFT CONFIGURATION

PLATFORM SUB-SYSTEMS

TELECOM MISSION REQUIREMENTS

PAYLOAD CONFIGURATION & EQUIPMENTS

RELIABILITY

OVERALL ELECTRICAL ARCHITECTURE

SPACECRAFT MASS & POWER BUDGETS

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SYSTEM REQUIREMENTS (Telecom 2 system)

FIXED SERVICE MISSION (telephony, mainly on French territories, 6/4 GHz)

SPECIALIZED SERVICE (digital data, mainly of continental Europe, 14/12 GHz)

MILITARY PAYLOAD (classified)

GEOSTATIONNARY SPACECRAFT

DEVELOPMENT OF 3 SPACECRAFT

initially 1 operational, 1 spare in orbit, 1 spare on the ground

finally 3 operational in orbit (1 main with guarant eed service, 2 with unguaranted service)

POSITIONS : 3 °EAST, 8 AND 5 °WEST, WITHIN +/- 0.05 °

ARIANE LAUNCH (dual launch)

LIFETIME > 10 YEARS

RELIABILITY > 0.75

TELECOM 2 SPACECRAFT CONFIGURATION IN ORBIT

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TELECOM 2 MECHANICAL ARCHITECTURE

FIXED ANTENNAS

DEPLOYABLE ANTENNA

DEPLOYABLE ANTENNA

THRUSTER

BATTERY

CORNET ANTENNAS

RADIATIVE AREAS

SOLAR ARRAY

PROPELLANT TANK

TELECOM 2 SPACECRAFT

CONFIGURATION

UNDER THE FAIRING

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STRUCTURE

Connection rods

North face

South face

Feed support

Tank support

Est face

Closing panels

Central tube

West face

SERVICE MODULE

Shear walls

EARTH

Main mounting walls

Connection rods

PAYLOAD MODULE

Central tube : carbon fiber

Walls : honeycomb with aluminium or

carbon fiber skin

Rods : carbon fiber or aluminium

Antenna reflectors :Front face white paintBack face : multilayer

High temperature thermal shieldto protect from apogee engine

East and West walls :multilayer insolation

Deployment mechanisms :Thermally decoupled & multilayer

Feed horns :Multilayer

Thrusters :High temperature multilayer

& heaters

Batteries :Thermally decoupledMultilayer & heaters

Internal face South and North walls :Heatpipes, heat sinks & heaters

External face South and North walls :Optical Sun Reflector

Internal structure :Black paint

Tanks :Thermally decoupledMultilayer & heaters

Upper wall : Multilayer

Sun Sensor :Thermally decoupledHeaters & multilayer

TH

ER

MA

L C

ON

TR

OL

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SUN CONFIGURATION

FOR GEOSYNCHRONOUS SPACECRAFT,

THE NORTH AND SOUTH FACES ARE VIEWING THE SUN WITH A MAXIMAL ANGLE OF # 23 °, THEY

ARE THUS THE MOST FAVORABLE ONES TO DISSIPATE HEAT

N

S

EQUATOR

23 °

ATTITUDE & ORBIT SUB-SYSTEM

Sun Acquisition Sensor + X

Sun Acquisition Sensor - X

Earth IRSensor

GyroAssembly

Sen

sors

’ele

ctro

nics

µµµµ Processor

Memory

Software

Wheels command

Thruster command

CDMS bus coupler

SA drive command

CDMS bus

ACTUATOR DRIVE ELECTRONICS

PILOTING UNIT

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CONCEPT OF ROLL & PITCH CONTROL

To + 6 hours

To

DUE TO THE ONBOARD

CINETIC MOMENTUM,

AN ERROR IN YAW (undetectable)

BECOMES AN ERROR IN ROLL

6 HOURS LATER

ATTITUDE CONTROL BY SOLAR SAILING

Windmill torque Neutral position Orthogonal to sun direction torque

γ n = - γ sγ n = γ s

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FINAL ORBIT ACQUISITION

Earth acquisition

ApogeeManeuvre (2)

Intermediate orbit

Drift orbit (nearly final GEO orbit)

Attitude determination

GTO

Despin,

solar array deployment

and sun acquisition

Kourou

PROPULSION

Thruster modules

Thruster modules Thruster modules

1 2 34

EARTH

EARTH

Thrust Apogee Engine

65

Thrust Apogee EngineLiquid Apogee Engine

Attitude & GEO thrusters Attitude & GEO thrusters

Apogee Engine

Propellant tanks

Pressurant tanks

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TM TCINTERFACE

PROTECTIONEOC

PROTECTIONEOC

HEATERS

PYRO -YPRIME

PYRO -YREDOND

HEATERS

PYRO +YPRIME

PYRO +YREDOND

BatteryControl

InterfaceUnit 1

Battery Control

Interface Unit 2

VOLTAGEREGULATION

VOLTAGEREGULATION

ASR

THRUSTERS

LINES & TANKS

BATTERY 2

THRUSTERS

LINES & TANKS

BATTERY 1

BU

S O

BD

H

BATT 2

BATT 1

BATT 1

BATT 2

ASR ASR

Actuator Drive

Electronics

Solar

Array-Y WING

SolarArrayWING +Y

POWER

BUS 1

POWER BUS 2

BAT 1 BAT 2

SA

DM

-Y

SA

DM

+Y

TM TCINTERFACE

Actuator Drive

Electronics

POWER SUPPLY

CHARGING CHARGINGBATT 1

BATT 2

RECEIVER 1C BAND

RECEIVER 2C BAND

BALISE TMC BAND 1

BALISE TMC BAND 2

TRANSPONDER1S BAND

TRANSPONDER2S BAND

AUTOMATICRECONFIGURATION

PROCESSEUR 1& SOFTWARE

PROCESSEUR 2& SOFTWARE

AOCS

BCIU 2

PIU 1

PIU 3

BCIU 1

PIU 2

MD 1

MD 2

MD 1

MD 2

Dire

ct T

C

PL 6 / 4

C

CORNETC BAND

CORNET TM

ANTENNAS BAND

OB

DH

B

OB

DH

A

MODULATOR 1

MODULATOR 2

DEMODULATOR 2

DEMODULATOR 1

Dire

ct T

C

CENTRAL INTELLIGENT UNIT

TELEMETRY/TELECOMMAND/RANGING

COMMAND & DATA HANDLING

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TELECOM 2 MISSION REQUIREMENTS : FIXED SERVICE

SERVICE : TELEPHONY

FREQUENCIES: 6/4 GHz

COVERAGE IN RECEPTION: GLOBAL

COVERAGE IN EMISSION: 5 SPOTS

- France

- French Antilles & Guyana

- Reunion Island

- St Pierre & Miquelon

- Central Africa

CAPACITY NEED: 10 channels

FREQUENCY DIVISION MULTIPLE ACCES

TELECOM 2 MISSION REQS : SPECIALIZED SERVICE

SERVICES: DIGITAL DATA

(data exchange, video-transmissions)

FREQUENCIES: 14/12 GHz

SAME COVERAGE IN RECEPTION AND

EMISSION: FRANCE

CAPACITY NEED: 11 channels

TIME DIVISION MULTIPLE ACCES

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TC 2 PAYLOAD CONFIGURATION FOR FIXED SERVICE

INP

UT

MU

LTIP

LEX

ER

COUPLER

Receiver

Receiver

EM

ITT

ING

AN

TE

NN

A

INP

UT

MU

LTIP

LEX

ER

OUTPUT MULTIPLEXER

AFRICA

SW

IHC

HE

S

OUTPUT MULT. GLOBAL

Channel 1

Channel 2

Channel 3

Channel 4

Channel 5

Channel 6

Channel 7

Channel 8

Channel 9

Channel 10

SWITCHES

OUTPUT

MULT. FRANCE

OUTPUT

MULT. SP&M

OUTPUT

MULT. ANT&GUY

SW.

SW.

SW.

SW.

SW

IHC

HE

S

RE

CE

IVIN

G A

NT

EN

NA

DETAILED PAYLOAD CONFIGURATION FOR FIXED SERVICE

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TC2 PAYLOAD CONFIGURATION FOR SPECIALIZED SERVICE

INP

UT

MU

LTIP

LEX

ER

Channel 1

Channel 2

Channel 3

Channel 4

Channel 5

Channel 6

Channel 7

Channel 8

Channel 9

Channel 10

Channel 11

DIPLEXER

Receiver

Receiver

DIPLEXER

RECEIVING ANTENNA

EMITTING ANTENNA

INP

UT

MU

LTIP

LEX

ER

OU

TP

UT

MU

LTIP

LEX

ER

O

UT

PU

T M

ULT

IPLE

XE

R

SW

ITC

HE

S

DETAILED PAYLOAD CONFIGURATION FOR FIXED SERVICE

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ANTENNAS

CORNET: EARTH GLOBAL COVERAGE ~ 17 °

VERY LARGE DISH AND

FOCAL PLANE WITH MULTI-FEEDS:

SHAPED COVERAGE

LARGE DISH REFLECTOR: SPOT COVERAGE

Useful beam width = 21 / Frequency / Diameter

(F in GHz and D in m)

ANTENNAS

FREQUENCY RE-USE: LINEAR POLARIZATION THANKS TO BI- GRID REFLECTOR

Focal Point VFocal Point H

Reflector for Vertical polarization

Reflector for Horizontal polarization

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RECEIVERS

FILTERING OF THE INPUT SIGNALS (to keep the ones fo r this spacecraft and reject the other)

VERY GOOD SENSITIVITY (incoming signal weak signal – free path losses ~10 - 20 !)

PRE-AMPLIFICATION TO INCREASE THE SIGNAL LEVEL

FREQUENCY SHIFT (-> ULTRA STABLE OSCILLATOR)

Ultra Stable Oscillator

ReceivingAntenna

Input Multiplexer

REPEATERS

FILTERING TO SEPARATED THE CHANNELS (output multipl exer)

ATTENUATOR TO FINE TUNING OF AMPLIFIER INPUT AND TH US OUTPUT

MASSIVE AMPLIFICATION OF EACH CHANNEL

FILTERING TO SUPPRESS GENERATED HARMONIC FREQUENCI ES (output multiplexer)

Receiver

Inpu

t Mul

tiple

xer

TC

Out

put M

ultip

lexe

r

TC

TC

Emitting Antenna

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FILTERS

RECEIVER:

KEEP ONLY THE INCOMING SIGNALS AT THE FREQUENCIES A LLOCATED TO THE SPACECRAFT

INPUT MULTIPLEXER:

SEPARATE THE VARIOUS CHANNELS FOR DEDICATED AMPLIFI CATION

OUTPUT MULTIPLEXER:

REJET THE NOISE GENERATED BY THE POWER AMPLIFICATIO N

CHARACTERISTICS:

• ATTENUATION

• « SHARPNESS »

• PHASE CHANGE

⇒ Butterworth, Tchebycheff,

Elliptical (with several poles)

Useful bandwith

Rejection bandh

Attenuation Ripples

Rejection

AMPLIFIERS

4 GHz: SOLID STATE POWER AMPLIFIERS OF 8W (redundancy : 14 /12)

11 GHz: TRAVELLING WAVE TUBES 50 W (redundancy : 15/11)

MAIN PROBLEMS: THERMAL CONTROL (low efficiency) AND NON LINEARITY (TWT)

Maximal output : 0

- 4

- 8

- 12

0 + 4- 4- 8- 12- 16

Input Backoff(dB)

Output Backoff (dB)

Saturation point

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GLOBAL

OPTIMIZATION

A - TWT AT SATURATION POINT

C/No down max, C/No up max, C/No intermod min

B - TWT VERY FAR FROM SATURATION

C/No down min, C/No up min & C/No intermod max

C - TWT FAR FROM SATURATION

C/No down medium, C/No up medium,

C/No intermod medium BUT C/No global MAX

C/No upC/No int

C/No down

A

B

C

C/No global

RECALL:

No/C global =No/C down+No/C up+C/Nointermod

Output back-off

Inpu

t bac

k-of

f

OTHER PAYLOAD EQUIPMENTS

CIRCULATOR:

AVOID SIGNAL PROPAGATION FROM OUTPUT TO INPUT B

COUPLER:

DIVIDE INPUT SIGNAL IN 2 OUTPUTS (with half power)

DIPLEXER:

ALLOW TO USE THE SAME ANTENNA FOR EMISSION AND RECE PTION

Input Output

P P/2

P/2

AntennaEmission

Reception

TRANSMISSION WIRING:

LOW POWER: CABLES 50 ohms

HIGH POWER, LONG LENGTH: WAVE GUIDE

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RELIABILITY: GENERAL

SINCE IN ORBIT REPAIRING/SERVICING IS IMPOSSIBLE, R ELIABILITY ANALYSIS ARE VITAL

TO COPE WITH LONG LIFETIME

RELIABILITY = PROBABILITY THAT A SYSTEM OPERATES CO RRECTLY IN A GIVEN ENVIRONMENT

MATHEMATICAL EXPRESSION: F(T) = exp (- λ(t) dt ), with λ failure rate

IN PRACTICE, THE FAILURE RATE OF ELECTRICAL COMPONE NTS FOLLOW A CURVE IN « BATHTUB »

0

T

λ(t) F(t)

tt

λλλλ(t) constantYouth Aging

1

RELIABILITY: CONSEQUENCES

WE USE HIGH RELIABILITY PARTS (HiRel), BUT THEY ARE VERY COSTLY BECAUSE THEY ARE

SCREENED AND TESTED DURING A FEW HOURS TO USE THE SURVIVING ONES WITH A CONSTANT

FAILURE RATE

TO IMPROVE RELIABILITY, REDUNDANCIES ARE IMPLEMENTED , BUT THIS IMPLIES SWITCHES AND

MAKE THE TESTS AND CONFIGURATION MANAGEMENT MORE CO MPLEX

WEAKEST ELECTRONIC PARTS: Variable resistors, Tunne l diodes, TWT, parts under high voltage/power

MECHANISMS ALWAYS A PB : HARD TO MODEL THEIR RELIABILITY, TESTS NOT REPRES ENTATIVE

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ELECTRICAL ARCHITECTURE

Military payload : Classified

SPACECRAFT MASS BUDGET

POWER SUPPLY 250 kg

electronics 35

batteries 120

solar array 95

ATTITUDE&ORBIT CONTROL 40 kg

PROPULSION 100 kg

TM/TC/RANGING/CDMS 30 kg

THERMAL CONTROL 60 kg

STRUCTURE 145 kg

WIRING 15 kg

DRY PLATFORM 640 kg

PAYLOAD 400 kg

BALANCING MASS 10 kg

DRY SPACECRAFT 1050 kg

PROPELLANTS 1150 kg

LAUNCH MASS 2200 kg

Payload

Propellantsfor Station Keeping

Propellantsapogee maneuvre

Power Supply

Structure

Propulsion

TMTC CDMSThermal control

AOCS

Wirings

PROPELLANTS ~ 50 % OF THE LAUNCH MASS !

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SPACECRAFT POWER BUDGET

MarginsLosses &

battery charging

Thermal Control

AOCSTMTC CDMS

Power supply

Emitted RF power

Payload(not emitted part)

PAYLOAD

PLATFORM

Power Supply

AOCS

TMTC CDMS

Thermal Control

LOSSES & BATTERY

CHARGING

TOTAL

2650 W

30 W

70 W

50 W

200 W

200 W

3400 W

2650 W

25 W

45 W

40 W

40 W

100 W

2900 W

Equinox Equinox

day eclipse

~ 90 % OF POWER CONSUMPTION DECOME HEAT !

Thanks for your attention

Questions ?