1

1

LISA Pathfinder and LISA

2

5 !106 km

Spacecraft(no mechanical contact)

Free falling

particles( 3 10-15 ms-2 Hz-1/2 @ 0.1 mHz)

Interferometer( 40 pm Hz-1/2 @ 3 mHz)

20 -3

Strain sensitivity

h 10 Hz @ 10 Hz!

"

GW at

0.03 mHz – 0.1 Hz

LISA

2

3

LISA essentials 1: the smart orbits

4

• Measurements on

detected sources:

- !" ~ 1’ – 1o

- !(mass,distance) # 1%

Angular Resolution with LISA

3

5

The measurement is split into two parts

6

The measurement is split into two parts

Two S/C to proof-mass measurements

One S/C to S/C measurement

4

7

SEND

1 W

RECEIVE

~200 pW (< 100 pW final)

Telescope

D ~ 30 cmArriving Beam

~20 km

1/2

4

222/1 pm/Hz 10

42!==

D

L

P

c

P

cS

sentreceived

L

"

#

"

$

"

$%

hh

Goal: keep all optical path errors within 40 pm/Hz1/2

LISA Interferometry

Shot Noise:

Laser divergence: YAG 1.06 µm

Laser transponding: outgoing light phase locked to incoming beam

L1

L2

3 5 million km arms: 33 sec 2-way light time

(1st interferometry null at 30

mHz)

8

Test

mass

Test

mass

LISA essentials 2: the laser transponding scheme

Power loss due to beam divergence makes interferometry

by reflection impossible

5!106 km

5

9

A Laser Transponder

10

The GW from difference of phase in adjacent arms

Laser phase noise common to both arms:

GW signal from difference: laser noise is suppressed

The standard GW

interferometer

6

11

LISA unequal arms confuse phases

Need to recombine light emitted at equal times

L

L±

10

5k

m

12

2L1/c

2L2/c

2L2/c

2L1/c2L1/c 2L1/c2L1/c

2L2/c2L2/c

2L2/c

2L1/c

( )noise

arm1t!"

Canceling laser frequency noise by time delay interferometry (TDI)

( )noise

arm2t!"

2L2/c

time

2L1/c

2L2/c

2L2/c

2L1/c2L1/c 2L1/c2L1/c

2L2/c2L2/c

2L2/c

2L1/c

( )h

arm1t!"

( )h

arm2t!"

2L2/c

( )h

arm1t!"= !

Frequency noise is canceled. GW is not

Arm-length to be known at ± 20 m

7

13

Laser Frequency Stability

14

Arm locking

• Cavity pre-stabilization is limited by the optical cavity length stability.

$L/L ~ 10-13 /! Hz

• The most stable length reference is LISA arm:

$L/L ~ 10-20 /! Hz

Phase locked laser in

distant spacecraft

represented by simple

mirrors

Simple model of LISA arm

8

15

• Laboratory tests

16

Laser Frequency Stability

9

17

Thrusters

Test-massCapacitive motion

sensor

Lisa essential 3: Drag-free control loop

18

10

19

Ac bias

Test

mass

injection

electrode Ac amplifier

PSD

The drag-free key elements: 1 the displacement

sensor

20

Ac bias

Test

mass

injection

electrode Ac amplifier

PSD

The drag-free key elements: 1 the displacement

sensor

11

21

x

y

z

!

"

#

! & y

# & x

" & z

The drag-free key elements: the displacement

sensor

Ac bias

Test

mass

injection

electrode Ac amplifier

PSD

22

2-4 mm gaps

<1 V ac-bias

No dc-voltage

(charging-losses)

Thermally

conducting

ceramics

(thermal

gradients)

AuPt low

susceptibility

test-mass

(magnetic noise)

12

23

10-4

10-3

10-2

10-1

100

10-11

10-10

10-9

10-8

10-7

10-6

Frequency (Hz)

S1/2

X

(m/Hz

1/2)

Pendulum down in air vac_test_125

XM

(X1-X

2)/2

No biasThermal

1 nm/%Hz resolution

4 mm gaps and 0.3 Volt bias

Requirement

24

Drag-free key elements 2: Microthrusters

13

25

LISA formulation study

26

14

27

28

Advanced

resonant

New

ton

ian

Gra

vit

ati

on

al

No

ise

8 frequency decades of GW astronomy

-VIRGO

15

29

LISA sensitivity

30

Massive Black Hole Binary

(BHB) inspiral and merger

Ultra-compact binaries

Extreme Mass Ratio

Inspiral (EMRI)

16

31

LISA

objec

tives

1/2

32

LISA

objec

tives

2/2

17

33

Binary Star in our Galaxy (White Dwarfs, Neutron

Stars)

Very bright signal (>100 times larger than noise)

Of some of them we know everything: they’re out

and waiting for being observed

34

class source dist (pc) f=2/P b (mHz)M1

M!

M2

M!

h SNR

(1 Year)

WD + WD WD 0957-666 100 0.38 0.37 0.32 4.00E-22 4.1

WD1101+364 100 0.16 0.31 0.36 2.00E-22 0.4

WD 1704+481 100 0.16 0.39 0.56 4.00E-22 0.7

WD2331+290 100 0.14 0.39 >0.32 2.00E-22 0.3

WD+sdB KPD 0422+4521 100 0.26 0.51 0.53 6.00E-22 2.9

KPD 1930 +2752 100 0.24 0.5 0.97 1.00E-21 4.1

AM CVn RXJ0806.3+1527 300 6.2 0.4 0.12 4.00E-22 173.2

RXJ1914+245 100 3.5 0.6 0.07 6.00E-22 195.0

KUV05184-0939 1000 3.2 0.7 0.092 9.00E-23 27.3

AM CV n 100 1.94 0.5 0.033 2.00E-22 35.6

HP Lib 100 1.79 0.6 0.03 2.00E-22 32.0

CR Boo 100 1.36 0.6 0.02 1.00E-22 10.6

V803 Cen 100 1.24 0.6 0.02 1.00E-22 9.2

CP Eri 200 1.16 0.6 0.02 4.00E-23 3.3

GP Com 200 0.72 0.5 0.02 3.00E-23 1.1

LMXB 4U1820-30 8100 3 1.4 < 0.1 2.00E-23 5.7

4U1626-67 <8000 0.79 1.4 < 0.03 6.00E-24 0.2

W UM a CC Com 90 0.105 0.7 0.7 6.00E-22 0.5

Signals from binary inspiral

18

35

36

1 0-4

1 0-3

1 0-2

1 0-1

1 00

Frequency (Hz)

1 0-2 3

1 0-2 2

1 0-2 1

1 0-2 0

1 0-1 9

1 0-1 8

Detection threshold (S/N = 5)

for a 1-year observation

RXJ1914.4+2456

4U1820-30

h

10

5

0

-5

-10

-15

mg w

(from Schutz)

WD Binary confusion limit

19

37

Chandra Deep Image

Supermassive

Black-Holes:

In the center of all

galaxies (likely)

38

Binaries from galaxy collisions

20

39

Visible

from

“every

where”

in the

Univer

se

40

21

41

A cosm

ological c

oordin

ate ladder

42

22

43

A recent

result in

numerical

relativity:

44

2!105M! at Z=5 + Simulated noise

23

45

Capture of small

Black-Hole by a super-

massive one

A Map of the Horizon

46

24

47

Gravitational Waves through

Time

JPL

48

• Production: Fundamental Physics in early Universe

– Inflation, phase transitions, topological defects, brane-

worlds, strings

• Non-thermal spectrum gives energies and masses

• Expressed as fraction of closure density

• Poorly constrained

Primordial Gravitational Waves

10 1014 5! !" <#gw

Simple Inflation

(max.)Nucleosynthesis

BoundLISA sees > 10-11

Covers 6 out of 9 orders of magnitude!

gw!

25

49http://astrogravs.nasa.gov/docs/mldc/

50

26

51

Is LISA feasible?

52

5 !106 km

Interferometer( 40 pm Hz-1/2 @ 3 mHz)

27

53

Parasitic force fluctuations

change distances and mimic gravitational waves

No parasitic force (acceleration) beyond

3!10-15ms-2/"Hz @ 0.1 mHz (3 hours)

Free falling

particles

54

28

55

56

Electrodes

Test-mass

Fiber

What can be done on

ground:

torsion pendulum

29

57

Achieving free motion in the horizontal plane (0 g)

58

30

59

Hollow proof-mass

for torsion

pendulum testing

60

Pendulum

suspension

and axis of

rotationseparation

gap

d

Sensing

electrodes

1 2

Test Mass

Sensor

housing with

electrodes

Torsion Fiber

Mirror for

Optical Readout

The single mass configuration: surface forces

geenerate torques

31

61

62

Two-degrees of freedom roto-

translational pendulum

32

63

Pendulum data converted into acceleration

64

LISA requirements

33

65

Galactic binaries signals

66

10-15

10-14

10-13

10-12

FNSHz!"#$%&

Testing quality of free fall

Torsion pendulum(surface disturbances)

LISA

34

67

LISA Pathfinder

• One 5-million-kilometer LISA arm squeezed

into one S/C

• Demonstrate relative acceleration within a

factor "10

68

LISA Pathfinder

• One 5-million-kilometer LISA arm squeezed

into one S/C

• + validation of the entire S/C to proof-mass

measurement

35

69

70

36

71

Test-mass

Test-mass

Interferometer

DLR

SSO

Test-mass

Test-mass

Test-mass

Test-mass

Interferometer

DLRDLR

SSOSSO

72

37

73

74

38

75

76

Pendulum: surface forces

39

77

LISA Pathfinder a full test

78

Science Objectives

40

79

80

UV Engineering Model

+

+

+

+

- - - -

41

81

The Big Bang Observer

• Shorter arms (5 104 km, not 5 106 km)

• More light (300 W, not 1 W)

• Bigger telescopes (3 m, not 30 cm)

• Better force isolation (.03 fm/s2/Hz1/2, not 3 fm/s2/Hz1/2)

• Multiple constellations for noise discrimination

! Need to subtract off signals from ALL NS-NS, BH-BH mergers in

universe in order to see background of gravitational radiation from big

bang .... Wow!

! year 2025 (????)