the lisa technology package on-board smart-2...

July 21, 2002-4th LISA Symposium S. Vitale 1

The LISA Technology Package on-board

SMART-2 and the test of free fall for LISAS. Vitale

Department of Physics, University of Trento, and INFN, Trento, Italy


ΛΤΠ

And the LISA Technology Package Architect Team

ESTEC Contract #15580/01/NL/HB


Detecting curvature by geodesic deviation

Difference of acceleration for

particle located at different places

xδ

metric2

ij j2

d h1 x2 dt

≈ δ

2 i2 i j

0 j02curvature

d x c R xdtδ = δ GW


2 22

1 hL

x LFm

∆ω + ωω

=δ2 22

1 hL

x LFm

∆ω + ωω

=δ

2

2

2

2F dd x

dth L

dtm+∆=δ

LISA sensitivity and the importance of free-fall

“Curvature”noise

Fourier2 2

21 h

Lx LF

m∆ω + ω

ω=δ

Parasitic forces Test-mass Separation


Importance of low frequency, an example:

LISA calibration binaries


LISA

( )12

215

a 2

f m 1S f 3 10 13 mHz s Hz

− ≤ × +

0.1 mHz f 30 mHz≤ ≤


5 106 km

SMART-2 In-flight test:

squeezing 1 LISA’sarm to 35 cm

214 msa 3 10 1 mHz f 30 mHz

Hz

−−δ ≤ ⋅ ≤ ≤


Test-masses(gravitational sensor) Interferometer

The LISA technology package (LTP)


Spacecraft

Test massx

Displacement sensor

Thrusters

High gain force feedback

Keeping the spacecraft with the proof-mass


Goal of the measurement:

LISA acceleration noise

Force on spacecraft

S C2T / Mp n 2

fbSensor noiseParasitic stiffnessForce on Test-Mass Drag free

gain

Relative diplacementTM wrt

nois

/

e

S C

Ff xm M

a

−

+ ω + ω

=

Force on spacecraft

S C2p n 2

fbSensor noiseParasitic stiffnessDrag free

gain


T / Mnoise

Force on Test-Mass

S/C

Fx

Mfam

−

+ ω + ω

=

Force on spacecraft

2T / Mnoise p

Parasitic stiffnessForce on Test-Mass


S Cn 2

fbSensor noiseDrag free

ga

S

in

/C

Fx

Mfam

−

= + ω ω

+

Force on spacecraft

2T / Mnoise p n

Sensor noiseParasitic stiffnessForce on Test-Mass


S C2fb

Drag freegain

S/C

FM

fa xm

−

= + ω

+ω

Force on spacecraft

S C2T / Mnoise p n 2

fbSensor noiseParasitic stiffnessForce on Test-Mass Drag free

gain

Relative diplacementTM wrt S/C

Ffa xm M

−

= + ω + ω


Purpose of the in-flight test

• Demonstrate ( )12

214

a 2


− ≤ × +

for 1 mHz f 30 mHz≤ ≤

• Independent measurement of the thrust noise level 2S C fbF Mω .

• Independent measurement of intrinsic fluctuating forces intf m

• Measurement of the stray stiffness 2pω of coupling between the test-mass and the spacecraft.

• Measurement of intrinsic sensor cross-talk and thrusters misalignments • Test of the low frequency suspension. • Test of the charge management procedures • Test of laser beam alignment via rotation of the test-mass • Test of the S/C attitude control scheme that uses the test-masses as a reference, as in the initial

beam acquisition scheme of LISA. • Test of the two-masses/two-axes control loop as in LISA. • Sensitivity to magnetic fields • Sensitivity to power fluctuations • Sensitivity to thermal gradients • Sensitivity to gravitational noise • Sensitivity to working point


x

y

z

φ

η

θ

TM1

TM2

Basic output:

TM distance as read by the laser interferometer


The basic mode of operation


( ) [

( ) ( )

( )

2 2 2 2 2 2lfs p2 n,laser lfs p2 n2 lfs

ActuationLaser Noise Baseline distortion noise

2 2lf

laser 2 2 2lfs p2

Stiffness ofsuspended TM

2 S / Cp12 n1 2

fbs p

1x

x

Fx

x x

M

ω + ω − ω + δ ω + ω + ω −

−

δ ≈ ×ω − ω + ω

ω + ω −

ω + ω

n

T M1

a

T M2

mf

mf

+

−


( ) [

( ) ( )

( )

2

laser 2 2 2lfs p2


2 2 2lfs p2 n,l

2 2lfs p2 n2 lfs

ActuationBaseline distortion n

aser

Laser Noise

2 S / Cp1 n1 2

f

oise

2 2lf

bs p2

1x

x

FxM

x x

δ ≈ ×ω − ω + ω

+ δ ω + ω + ω −

− ω + ω

ω + ω − ω

ω + ω

−

n

T M1

a

T M2

mf

mf

+

−


( ) [

( ) ( )

( )

laser 2 2 2lfs p2


2 2 2 2 2lfs p2 n,laser lfs p2

Laser Noise Baseline distor

2n2 lfs

Actuationnoise

2 2lfs p2

tion

2 S / Cp1 n1 2

fb

1x

x

FxM

xx

δ

+ ω −

−

≈ ×ω − ω + ω

ω + ω − ω + δ ω + ω

ω + ω

ω + ω

−

n

T M1

a

T M2

mf

mf

+

−

Thermalstability


( ) [

( ) ( )

( )

laser 2 2 2lfs p2




2 2lfs

2 S / Cp1 n1 2

b2

fp

1x

x x x

FxM

δ ≈ ×ω − ω + ω

ω + ω − ω + δ ω + ω + ω −

ω + ω

− ω + ω − n

T M1

a

T M2

mf

mf

+

−Use Laser


( ) [

( ) ( )

( )

laser 2 2 2lfs p2




2 2lfs

2 S / Cp1 n1 2

b2

fp

1x

x x x

FxM

δ ≈ ×ω − ω + ω

ω + ω − ω + δ ω + ω + ω −

ω + ω

− ω + ω − n

T M1

a

T M2

mf

mf

+

−

( ) [

( ) ( )

( )

laser 2 2 2lfs p2




2 2lfs

2 S / Cp1 n1 2

b2

fp

1x

x x x

FxM

δ ≈ ×ω − ω + ω

ω + ω − ω + δ ω + ω + ω −

ω + ω

− ω + ω − n

T M1 T M2

a

f fm m

+ −

Intrinsically a gradiometer


2 2 2lfs p2 p12 0 ω ≈ −ω ≈ −ω ≥

( ) [

( ) ( )

( )

laser 2 2 2lfs p2




2 2 2 S / Clfs p2 p1 n1 2

fb

1x

x x x

FxM

δ ≈ ×ω − ω + ω

ω + ω − ω + δ ω + ω + ω −

− ω + ω − ω + ωn

T M1 T M2

a

f fm m

+ −

( )2 -2

pω s

(Hz)

Fig. 1. Open loop gain (red line) and overall coupling stiffness (yellow line) for one possible controllaw for the low frequency electrostatic suspension.

2 2 2 2lfs p2 p1 p1 2ω + ω − ω ≈ ω


ID Action

14 Main loop 15 Control to science mode16 Transfer from accelerometer mode to low freq. Suspe17 Attitude to hybrid mode18 Discharge19 Charge measurement20 Discharge21 Transitory decay22 Final laser beam alignment23 Measurement phase24 M1 basic measurement25 M1 double-check26 Interchange 1 and 227 Transitory decay28 Measurement29 Transfer to Accelerometer Mode

Main loop 21 h5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

2 3


( ) ( ) ( ) S / C,x2 2 2 2xlaser p2 n,laser p2 p1 n,1 22 2 2

fb,xlfs2 p2

F1 fx x xm M

∆δ ≈ ω − ω + + ω − ω + ωω + ω − ω

Locking onto the laser output


Stiffness measurement, adding a signal in the drag-free control loop

x


x


2p1

laser cal2

2x x

ωδ ≈

ω


3× +


Θ

xLTP

xDRS

h DRS-LTP an enhanced testopportunity


Table 1 Summary of LTP-DRS accommodation trade-off

Θ(°) 2-axes 2-masses control with separate packages

Correlation analysis between packages

Redundancy for loss of 1 IS

Gravitational calibration maximum

SNR 0 No Full Yes 215

30 Marginal Yes Yes 165 45 Yes Yes Yes 135

60 Closest to LISA Configuration Yes Yes 138

90 Yes No No 121


Table 1. Amplitude of achievable calibration signals with 100 µm displacement of TM

Θ(°)

LTP test-masses difference of acceleration

( fms-2) for 100 µm displacement of DRS TM

along xDRS



along yDRS



along zDRS 0 249 0 125 30 170 130 161 45 82 172 193 60 14 155 220 90 114 57 242


Requirements


( )12

214

a 2


− ≤ × +

1 mHz f 30 mHz≤ ≤


S/C and external disturbance

Apportioning

LTP

Inertial Sensor

Table 1. Allocated contributions to the overall noise budget for LISA and SMART-2

SMART-2

( )3 210 f Hz 3 10− −≤ ≤ × LISA

( )4 110 f Hz 10− −≤ ≤ Source IS

2intp n

IS sources

f xm

+ ωOut

S C2intp 2

fb

Extrernal sources

Ffm M

+ ωω

IS2intp n

IS sources

f xm

+ ωOut

S C2intp 2

fb

Extrernal sources

Ffm M

+ ωω

21

LTP S/C

Allocated contribution 2 2

15 f ms10 13 mHz Hz

−−

× +

21

15 15

2.1 2.1


Apportioning complicated by non-linearity

( )

( )

noise

IS sources

LTP

S / C+Extern

LT

2 2 2pIS pLTP pS / C n

S C2 2 2pIS pL

al source

S /

PT /

TP

s

IST /

pS /

M

CT / M

C

M

2fb

a

fm

fm

f x

FM

m=

+

+

+ ω + ω + ω

+ ω + ω + ωω

( )

( )

noise

IS sources

LTP

S / C+Extern

LT

2 2 2pIS pLTP pS / C

2 2 2pIS pL

S / CS CT

I

/TP pS /

al sources

S

M

T

PT / M

C

/ Mn

2fb

a

fm

Ffm

f x

M

m=

+

+

+ ω + ω + ω

+ ω + ω + ωω

( )

( )

noise

IS sources

LTP

S / C+Externa

2pLTP

LTP

IS2T / M 2

pS / C

S / CS C2T

l source

/ MpS / C

pIS n

2pI 2

fbS

T / M

2pLTP

s

Ffm

f

ma

M

x

m

f= + + +

+

+

ω

ω +ω+ω

+ ω

ω ω

Independent requirement needed for stiffness


22 7 2p

f4 10 1 s3 mHz

− − ω ≤ × +

LISA

( )22 15 2p S/ Cx 1 10 1 f 3mHz m s− − ω ≤ × +

SMART-2

5×

2×10×


Table 1. Top level requirement for stiffness along the sensitive axes.

SMART-2

( )3 210 f Hz 310− −≤ ≤ LISA

( )4 110 f Hz 10− −≤ ≤ Source

External sources IS sources External sources IS sources

LTP S/C Allocated contribution 2

7 2f10 1 s3mHz

− − × +

5 5 10 1 3

Extra stiffness due to actuation

2 Maximum ForceStiffnesseffective gap

×≈


Cross-talk

2x,cross talk x,

S / C wrt T/Mcoupling motion along stiffness

f − = ω × ∆#

#

#

•Actuation: force applied along wrong DOF

•Sensing: sensor detects motion along wrong DOF

•Dynamical: parasitic springs have off-diagonal terms


Table 1 Drag-free and attitude control requirements and displacement noise allocation in M1

Units Frequency range

Attitude 910 rad Hz−×

Displacement ×10-9 m/√Hz ( )3 210 f Hz 310− −≤ ≤

2 2S C fb ,x S C fb ,xF M , Iω Γ ω Total control

level Ref. Num DOF

xn /θn

ψ =0.01 (≈0.6°) ψ =0.1 (≈6°) ψ =0.01 (≈0.6°)

ψ =0.1 (≈6°)

1 xS/C 1.8 4.7 5 5 2 No

measurement on y

1.8 47 4.7 50 5

3

y2,S/C

Measurement on y 1.8 4.7 5 5

4 No measurement

on y 1.8 66 6.6 69 6.9

5

y1,S/C

Measurement on y 1.8 6.6 6.6 9.5 9.5

6 z1S/C 18 47 4.7 50 19 7 z2S/C 18 66 6.6 69 19 8 θ1S/C 65 235 23.5 243 68


Other non linear effects

Magnetic field: force ∝ B2

Electric field : force ∝ E2


LISA SMART-2 Ref. Num. Requirement

IS S/C IS LTP S/C

1 Magnetic field

maxB

(µT) 3 4 3 3 4

2 Magnetic field gradient ( )x y,zB

x(y, z)

∂

∂

(µT/m)

4 3 4 35 31

3 Magnetic field fluctuation BS

(nT/√Hz) 71 71 71 353 353

4 Magnetic field gradient PSD B xS∂ ∂

(µT/m)/√Hz 0.71 0.71 0.71 3.5 3.5


Table 1 DC force requirements

Ref num Case Fx/m (ms-2) Fz/m (ms-2)

1

LISA Electrostatic

suspension on sensitive axis

TBD TBD

2

LISA No electrostatic suspension on sensitive axis

10-9 (limited by thrusters)

TBD

IS LTP S/C IS LTP S/C

3

SMART-2 Important notice: in M1 the figure

includes the effect of S/C acceleration

along x on TM2

2.5×10-10 2.5×10-10 2.5×10-10 0.35×10-9 0.35×10-9 0.8×10-9


The special case of gravitational force

Accuracy requirements

112

mg 10s

−−∆ ≈

Gradients, cross-coupling 1%

1 2 6g

5

S 3 10 1 Hz LISAg 3 10 1 Hz SMART-2

−

−

×≤

×


Point-like approximation for test-mass breaks down for close sources

Analytical formula found for point-like source and parallelepiped test-mass

( )sF F r=Force

sr

Source

COM ( )s

s

dF rdr

Γ = −Gradient

COM sT r F= ×Torque

( ) ( )s sˆ ˆ r∂ = φ × − φ ⋅ × ∇

∂φAngular derivatives

Analytical formula for F Analytical formula for everything


A sample spacecraft

Errors infield

estimate


Non-homogeneous “boxes”


Table 1 Recommended values for gravitational field requirements verification Parameter Element Value Parameter Element Value

LTP/DRS 10-3kg Attitude error All elements 0.3° Inner and radial

panels 10-3 kg LTP/DRS 0.5 mm Mass Boxes and outer

panels 5 10-3kg LTP-OB 0.2 mm

LTP- OB 5 mm

Location error

All other elements 1 mm

DRS and LTP IS2 1 cm LTP and DRS elements.

Boxes, Inner panels, radial panels

10%

Inner and radial panels 3 cm

Uncertainty on mass distribution

Heavy structural elements, LTP-OB 2%

Mesh size

Outer panels and boxes 4 cm


12

34


Table 1 Summary of gravitational balance calculation results

Configuration

Mass (kg)

Minimum meshing

(mm)

Homogeneity(%)

Position (µm)

Attitude(°)

Mass uncertainty

(kg)

Resulting gradient

(s-2) 1 6.25 4 2 50 0.5 10-3 6.9×10-7 2 18.06 4 2 100 0.5 2×10-3 7.5×10-8

3 1.29 2 5 50 0.5 5×10-4 1.2×10-6 4 2.78 2 5 50 0.5 5×10-4 4.9×10-8


It’s not the complete story


Charging

Random arrival of charge on test-mass


Charge interacts with stray dc voltage

Random force


The random part

( ) 1 21 216 V

12o eff

S m 15 mm 0.1mHz3.7 10m 5 mV 16 s fs Hz

−−

ω σ λ = ×

tot eff toteff eff

C d C Cd 15mmC 2 mm 7

≈ =

λ TBC poor margin: aim at largest gap

(in all directions)


The LTP key elements: 1 the displacement sensor

Ac bias

Test mass

injection electrode Ac amplifier

PSD

x

y

z

θ

φ

η

θ & y

η & x

φ & z


Top and Bottom

Lids

Central frame

Test Mass

Electrodes


144mm 174mm

295.2mm


Man

uel R

OD

RIG

UE

S -B

erna

rd F

OU

LON

-1

-ES

TEC

Nor

dwijk

-

Febr

uary

2002

-

4FEEU (Front End Electronics Unit) SCHEMATIC

Vd

DVA

DVA

ProofMass

Possens ADC

DAC

DAC

FPGA

Clock

Serialinterface

Power Supply PrimaryPower Line

Computer

5Vrms

MechStop

Inj Elec

+

+

July 21, 2002-4th LISA Symposium S. Vitale 66© Astrium

Nonpolarizing MZ ifo: robust version (3)

The optical bench contains 3 single interferometers to measure:•the distance between the T/Ms x1-x2•the distance between T/M1 and the optical bench x1•a reference phase•tilt of T/M1.

The LTP key elements: 2 optical metrology

Distance between test-mass 1 and test-mass 2

Distance between test-mass 1 and optical bench

2 relative angles between t.m.1 and t.m 2

2 angles of t.m. 1

A test for optical readout


AOM bench


LTP key elements: 3 Control and Software

Drag-free and attitude control for the spacecraft

The spacecraft cannot follow both test-masses at once

Actuation needed on 1 test-mass also along the sensitive axis


LTP is an automous dynamical system

Force noisemodel

Mq-1 1/s2

Electrostaticreadoutmodel

IS noise

Electrostaticsuspension

Laserreadoutmodel

Interferometernoise

fnoise

q*q*..

factuation

Kh

Spacecraftmotion

Spacecraftdistortion

CSC

Mu

nSC

u..

LTP modelS/Cmodel

fho,fLTPo

Sensit. to noise(Bfhf,BfLTPf)

Fsc

Fsc

Drag free control and actuation system

KLTP

q

CLTP

LTPdistortion

nLTP

-

Bfhf

BfLTPf

q

q̂

q


Compensating negative stiffness kp= 10-7 N/m

1.¥ 10-6 0.00001 0.0001 0.001 0.01

10

100

1000

10000

parasitic

Gk

frequency[Hz]

p 5k1 5 10 Hz2 m

−= ×π

and dc forces

10-10N/10-7 N/m 1 mm


Optimised control

Robust against knowledge of parameters


Numerically implementable as ARMA


DC comp. a

DC comp. b

TM stabiliz a

TM stabiliz b

SCIENCE MODE

Suspension c

ACCELEROMETER MODE

Low frequency sine wave

Charge measurement

dither

Poles, zeroes, gain

Suspension switchx1,…,x6

Transfer functions

parameters upload

Threshold detector

Caging command

Charge measurement

command

Ch1, ch2,…

External command

DC force offsets

Fd1,…, Fd6

Capacitive actuation functional block diagram

Suspension d

LARGE AMPLITUDE MODE

TBC

Transfer functions selection

Channels combinator

Calibration parameters

upload


DC comp. a

DC comp. b

TM stabiliz a

TM stabiliz b

SCIENCE MODE

Suspension c

ACCELEROMETER MODE


Charge measurement

dither

Poles, zeroes, gain


Transfer functions

parameters upload

Threshold detector

Caging command

Charge measurement

command

Ch1, ch2,…

External command

DC force offsets

Fd1,…, Fd6


Suspension d


TBC


Channels combinator


upload


Accelerometer mode

High damping, large force

( )2 2

122 2 2 1a o 2

2 212

2

sss ss

+ + ωω τω = ωω + + ω

τ

max2

F m0.15m s−

µ≤


Transition to-from accelerometer mode

Requested to damp long term transitory

Needs adjustment of long term behaviour


Test-mass acquisition


DC comp. a

DC comp. b

TM stabiliz a

TM stabiliz b

SCIENCE MODE

Suspension c

ACCELEROMETER MODE


Charge measurement

dither

Poles, zeroes, gain


Transfer functions

parameters upload

Threshold detector

Caging command

Charge measurement

command

Ch1, ch2,…

External command

DC force offsets

Fd1,…, Fd6


Suspension d


TBC


Channels combinator


upload


Com

man

d

V1,…, V12F to V

conversion2

F to V conversion

2

Switch

Capacitive model equation

parameters upload

Carrier waveform parameters

upload

Capacitive actuation

1

Fd1,…, Fd6

Carrier waveform synthesis

3

ISFEE DAC

4

TM

Optical metrology

Capacitivesensing

V1(t)..V12(t) forces

ADC

Switch Commandx1,…,x6ADC


Com

man

d

V1,…, V12F to V

conversion2

F to V conversion

2

Switch


parameters upload


upload


1

Fd1,…, Fd6


3

ISFEE DAC

4

TM

Optical metrology

Capacitivesensing


ADC



Actuation by frequency modulation of carrier

To suppress thermal noise and charge effect by suppressing dc-voltages


Com

man

d

V1,…, V12F to V

conversion2

F to V conversion

2

Switch


parameters upload


upload


1

Fd1,…, Fd6


3

ISFEE DAC

4

TM

Optical metrology

Capacitivesensing


ADC



12

4

35 6

8 7

10

9

1314

11

12x

y

z

Force to voltage conversion

1 carrier frequency per DOF DOF are independent

Test-mass V=0No-cross-talk

x ox

K df2

≤Max force

L

x

φ

Force,no torque

Constant stiffness

linear control


©Astrium90 Smart-2 Final Presentation 12/07/2002

Frequency Analysis – X axis acceleration (1 of 3)

10-4 10-3 10-2 10-110-14

10-13

10-12P S D totaleFx1 force nois eFy1 force nois eFz1 force nois eTheta1 force nois eEta1 force nois eP hi1 force nois eFx1 readout nois eFy1 readout nois eFz1 readout nois eTheta1 readout nois eEta1 readout nois eP hi1 readout nois e


LTP key elements 4: Monitoring the environment

MagnetometerParticle detector

+ solar radiation monitor


Pulling all together


LTP Sensor / Optical Bench / Structure Architecture


< 85 kg


< 110 W


LTP main boxMass = 43 kgPower = <0.1WDimensions = 600mm (length)

354 mm(diameter)

IS-FEE #1Mass = 3.5kgPower = 7.4 WDimensions =240x200x170mm

IS-CMS electronics+UV lampMass = 6 kgPower = 8(0.8)W (quiescence)Dimensions = 165x130x60mm

IS-CM electronicsMass = 1 kgPower = 18WDimensions = 240x150x20mm

Processor and diagnosticsMass = 4.2kgPower = 35 WDimensions = 260x200x80mm

Phase detector FEEMass = 1 kgPower = 15 WDimensions =200x200x100mm

Laser systemMass = 5 kgPower = 20 WDimensions =150x200x200mm

S/C Power

IS-FEE #2Mass = 8.5kgPower = 7.4WDimensions =240x200x170mm

28V PowerRS 422Electrical wireOptic fiber

MagnetometerMass = 0.5 kgPower = 0.6 WDimensions = 45x143x80mm

Particle DetectorMass = 2.5 kgPower = 2.6 WDimensions = 95x122x217mm

AOM Mass = 2 kgPower = 15 WDimensions =200x200x100mm

To S/C bus


A key element for the test: micropropulsion

July 21, 2002-4th LISA Symposium S. Vitale 1008-04-2002-DRS LTP Meeting S. Vitale 80

SMARTSMART--22 LTPLTP--ArchitectArchitect



LISA satellite

• Dedicated LISA spacecraft forms basis of mission- Dedicated internal space for separate LTP and DRS

panels allows orientation of sensitive axes as required.

- Height 900mm overall- Communications antennas positioned for L1 orbit,

two 5cm X-band horns provide overlapping coverage. X-band patches for omni coverage

• Simultaneous operation of LTP and DRS accommodated by oversizing solar array (2 m2. )

- Solar panel also mounts antennas, sensors, lifting points

- Some scope to increase sunshield diameter for top spacecraft, but 2m constraint used

• This configuration is the basis for all detailed structural, thermal, GNC analyses carried out in phase 3 LISA satellite includes cold gas for station

keeping, plus 4 FEEP clusters

LTP and DRS stacked for independent axis alignment



Structural Design

• Structure design based on filament wound octagonal facetted cylinder

- Diameter and taper easily variable

• Concept designed and tested for launch stacked using pyro bolt attachments

- STM Statically tested to loads equivalent to stack above 800kg

- Sine tested above 350kg- Extensive correlation provides

confidence in FE modelling

• Very stable and low distortion structure, with few parts to minimise hysteresis

- Equipment simply bolts through



Orbit options

• Extensive range of orbits studied, and missions to each designed:- Geostationary- Highly elliptical- Weak stability (new set of “stable” orbits described)- Earth-Sun Lagrange points- Heliocentric drift away orbits

• Geostationary and HEO options place strong constraints on technology demonstration

• WSB, Lagrange and Drift-away orbits all special cases of family which provide excellent conditions for the demonstrations

• Lagrange point orbits provide the best combination of communications and thermal stability

- L1 chosen for easiest compatibility with Ariane launch.



Launch options, via GTO or similar medium altitude intermediate orbit

• For missions from the Ariane 5 standard GTO, the required velocity increment to raise the apogee to 1.3 million km is about 760 m/sec.

• An Ariane 5 launch requires:- After apogee raising, orbit insertion manoeuvres of up to

110 m/sec to reach a baseline 1000000km radius halo orbit. - Implies limited launch window restrictions in May/June to

avoid excess DeltaV overhead

- Total transfer dispersion corrections/losses are approximately 20 m/s

Launch vehicle injects intointermediate orbit

Mult iple burns to

raise apogee to L1

Injection intoHalo orbit

Approx 2 million km

View on ecliptic


S M A R T - 2

Mission Definition Study

PHASE 3

Page 16Final ReviewFR. ESTEC, Noordwijk, July 11th 2002

·

Exec

utiv

e S

umm

ary

·

· The LTP experiment


· The SAT A experiments and ACS· The SAT A experiments and ACS+POWER· The SAT A experiments and ACS+POWER+ COMMUNICATIONS· The SAT A experiments and ACS+POWER+ COMMUNICATIONS+OBDH


S M A R T - 2


PHASE 3


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Exec

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· The SAT A experiments and ACS+POWER+ COMMUNICATIONS+OBDH+STRUCTURE AND THERMAL CONTROL

Unit TotalDimensions (mm)

Mass (kg)EquipmentSubsystem #

Power (W)

uN Thrusters Cluster 140 x 140 x 50 4 2,5 10 28uN Thrusters PCU 250 x 165 x 200 4 3,5 14 24Fine & Coarse Sun Sensor 100 x 100 x 20 3 0,5 1,5 2Star tracker 140 (D) x 230 (L) 1 2,5 2,5 10

ACS & Propulsion – Total 28 64

ACS / Propulsion

Solar Array (Solar Cells) 1800 (D) x 70 (t) 1 2,5 2,5 0Battery 160 x 120 x 75 1 2,5 2,5 1PCDU 100 x 270 x 125 1 4,6 4,6 6,5

Power - Total 9,6 7,5

Power

Transponder + Amplifier 275 x 110 x 197 1 6 6 37High gain Antenna 500 (D) x 180 (L) 1 3 3 0Low gain Antenna 6 (D) x 25 (L) 2 0,5 1 0

Communications - Total 10 37

Communications

Computer 236 x 165 x 178 1 6,4 6,4 16RTU 237 x 165 x 128 1 4,7 4,7 6,5

OBDH - Total 11 22,5

OBDH

Structure 1 32,7 32,7 0Bracketery 1 12,3 12,3 0Harness Distributed 1 4 4 7SATELLITE COMPEN MASS 4 7

Structure - Total 56 7

Structure

Heaters / TC Various TBD 1 1 6MLI Various TBD 2 2 0Radiators Various TBD 1 1 0

Thermal Control - Total 4 6

Thermal Control

Satellite A total Mass: 272 kg (nominal) / 292 kg (with margin)


S M A R T - 2


PHASE 3


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- DDVProgrammatic considerations (12/16)M

ore

deta

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info

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M2-

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CONSOLIDATION OFLTP DEFINITION

SMART-2

STUDY 2

TWO CONTRACTORS IN PARALLELPERFORM THE

MISSION DEFINITION PHASE

A-PRE B

TODAY

LISA

1.04 12.05 3.07 3.11

DEFIN.B/C/D

ITTITT

6.01

9.01

Preliminary Design Review

3.05 8.115.03

ITT B

Launch

LCC/DB

STUDY 1 2.03

C/D

8.06

10.61.07

LAUNCH

PREPARATION

6.02

6.0611.03

ITT B/C/D ITT

LISADEMOLAUNCH

CAMP.COMMISS.


Testing quality of free fall

10-15

10-14

10-13

10-12

FNSHz

Torsion pendulum (surface disturbances)

SMART-2

LISA

the lisa technology package on-board smart-2...

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