LISA ( 3 10 -15 ms -2 Hz -1/2 @ 0.1 mHz) Spacecraft Interferometer - - PDF document

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LISA ( 3 10 -15 ms -2 Hz -1/2 @ 0.1 mHz) Spacecraft Interferometer - - PDF document

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2/24/2009 Free falling particles LTP LTP LISA ( 3 10 -15 ms -2 Hz -1/2 @ 0.1 mHz) Spacecraft Interferometer (no mechanical contact) ( 40 pm Hz -1/2 @ 3 mHz) GW detection by macroscopic test- mass laser tracking: LISA, LISA Pathfinder and

slide-1
SLIDE 1

2/24/2009 1 GW detection by macroscopic test- mass laser tracking: LISA, LISA Pathfinder and the fundamental limitations.

Stefano.Vitale@unitn.it

Firenze February 23, 2009

  • S. Vitale

1

LTP LTP

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)

LISA

Firenze February 23, 2009

  • S. Vitale

2

5 ×106 km

20

  • 3

Strain sensitivity h 10 Hz @ 10 Hz

−

≈ GW at 0.1 mHz – 0.1 Hz

LISA’s smart orbits

Firenze February 23, 2009

  • S. Vitale

3

  • Measurements on

detected sources:

  • Δθ ~ 1’ – 1o
  • Δ(mass,distance) ≤ 1%

Firenze February 23, 2009

  • S. Vitale

4

slide-2
SLIDE 2

2/24/2009 2

LTP LTP

Ac bias Test mass injection electrode Ac amplifier PSD

displacement sensor

Firenze February 23, 2009

  • S. Vitale

5

LTP LTP

Ac bias Test mass injection electrode Ac amplifier PSD

displacement sensor

Firenze February 23, 2009

  • S. Vitale

6

Optical readout along the sensitive axis LTP LTP

  • Drag-free along

sensitive direction

  • Test-mass control

along the remaining

  • nes

Firenze February 23, 2009

  • S. Vitale

7

x y z θ φ η θ & y η & x φ & z LTP LTP

  • 2 kg Au-Pt

test-mass

Firenze February 23, 2009

  • S. Vitale

8

  • 4 mm gaps
slide-3
SLIDE 3

2/24/2009 3

The laser 2-ways Doppler link

Firenze February 23, 2009

  • S. Vitale

9

A Laser Transponder

The GW from difference of phase in adjacent arms The standard GW interferometer

Firenze February 23,

  • S. Vitale

10

Laser phase noise common to both arms: GW signal from difference: laser noise is suppressed LISA unequal arms confuse phases

L±105km

Firenze February 23,

  • S. Vitale

11

Need to recombine light emitted at equal times

L

Firenze February 23,

  • S. Vitale

12

slide-4
SLIDE 4

2/24/2009 4

LTP LTP

Firenze February 23, 2009

  • S. Vitale

13

Firenze February 23, 2009

  • S. Vitale

14

Firenze February 23,

  • S. Vitale

15

vitational Noise

Firenze February 23, 2009

  • S. Vitale

16

Newtonian Grav

slide-5
SLIDE 5

2/24/2009 5

Galactic binaries

Firenze February 23, 2009

  • S. Vitale

17

Supermassive BH In the center of (all) galaxies Form binaries upon galaxies collision Strong SNR

Massive Binary Black Holes: strong signals

Redshift Contours of SNR, equal mass merger (optimal) Firenze February 23, 2009

  • S. Vitale

18 Mass Firenze February 23, 2009

  • S. Vitale

19

Black-hole merger tree

Firenze February 23, 2009

  • S. Vitale

20

slide-6
SLIDE 6

2/24/2009 6

Firenze February 23, 2009

  • S. Vitale

21

Experimental demostration of Hawking theorems: Growth of BH area No-hair theorem

LISA Pathfinder LISA Pathfinder.

  • S. Vitale

22 Firenze February 23,

LTP LTP

The basic element of one LISA arm: the “Doppler link”

  • S. Vitale

23 Firenze February 23, 2009

LTP LTP emitter am

The basic element of one LISA arm: the “Doppler link”

  • S. Vitale

24 Firenze February 23, 2009

receiver em-bea

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SLIDE 7

2/24/2009 7

LTP LTP

Measuring relative velocity along the line of sight ( ) ( )

( )

light emitter receiver

c k v t L c v t 2

μ μ μ

Δν = − ⋅ − − π

emitter

v

  • emitter

am

light

k

  • S. Vitale

25 Firenze February 23, 2009 receiver

v

  • receiver

em-bea LTP LTP

( ) ( )

( )

light emitter receiver

c k v t L c v t 2

μ μ μ

Δν = − ⋅ − − π

( ) ( )

( )

light emitter receiver

c k v t L c v t 2

μ μ μ

Δν = − ⋅ − − π

Time delay: to be pictured in space-time

y

emitter

v

  • light

k

  • emitter

v

  • light

k

  • S. Vitale

26 Firenze February 23, 2009

x t

receiver

v

  • L

receiver

v

  • LTP

LTP

What does change relative velocity along the line of sight?

y

emitter

v

  • light

k

  • S. Vitale

27 Firenze February 23, 2009

x t

receiver

v

  • LTP

LTP y

emitter

v

  • light

k

  • What does change relative velocity along the line of

sight?

  • S. Vitale

28 Firenze February 23, 2009

  • Gravity:

– Parallel transport

x t

receiver

v

slide-8
SLIDE 8

2/24/2009 8

LTP LTP

What does change relative velocity along the line of sight?

y

emitter

v

  • light

k

  • Rotation of the line of sight
  • S. Vitale

29 Firenze February 23, 2009

x t

receiver

v

  • 29

LTP LTP

What does change relative velocity along the line of sight?

y

emitter

v

  • light

k

  • True forces that accelerate test-masses
  • S. Vitale

30 Firenze February 23, 2009

x t

receiver

v

  • LTP

LTP

What does change relative velocity along the line of sight?

y

emitter

v

  • light

k

  • Interferometer measurement noise
  • S. Vitale

31 Firenze February 23, 2009

x t

receiver

v

  • LTP

LTP

The problem of staged links

Test- mass Test- mass Body (spacecraft,

  • ptical bench..)

Body (spacecraft,

  • ptical bench..)

Body (spacecraft,

  • ptical bench..)

Firenze February 23,

  • S. Vitale

32

  • Links are split as test-masses cannot carry optics
  • Perfect split is insensitive to motion of body (bodies)
  • Misalignments, calibration errors mix motion of extra bodies in
slide-9
SLIDE 9

2/24/2009 9

LTP LTP

An Input-Output Description

D l A GW- Diff i l Parasitic Differential Forces Difference of Force Relative Displacement Displacement readout noise

Firenze February 23, 2009

  • S. Vitale

33

Doppler Arm Differential Acceleration p Other bodies displacement LTP LTP

An Input-Output Description

D l A GW- Diff i l Parasitic Differential Forces Difference of Force Relative Displacement Displacement readout noise Equivalent force

Firenze February 23, 2009

  • S. Vitale

34

Doppler Arm Differential Acceleration p Other bodies displacement Equivalent force LTP LTP

Differential acceleration performance

Parasitic acceleration of test- masses

Firenze February 23, 2009

  • S. Vitale

35

Measurement noise

2 eq

a x δ ≈ ω δ

LTP LTP

Differential acceleration performance

A “Universal” plot

Firenze February 23, 2009

  • S. Vitale

36

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SLIDE 10

2/24/2009 10

LTP LTP

GP-A

Firenze February 23,

  • S. Vitale

37

LTP LTP

Cassini

Firenze February 23,

  • S. Vitale

38

LTP LTP

Microscope

Firenze February 23,

  • S. Vitale

39

LTP LTP

GOCE-Grace

Firenze February 23,

  • S. Vitale

40

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SLIDE 11

2/24/2009 11

LTP LTP

Firenze February 23, 2009

  • S. Vitale

41

LTP LTP

Testing on Ground

  • Surface forces

– Mostly originated from the nearest surroundings of test-mass

  • Volume forces

– Magnetics – Locally generated gravitation

Firenze February 23, 2009

  • S. Vitale

42

LTP LTP

Test-mass nearest surroundings and shield: the GRS

Firenze February 23, 2009

  • S. Vitale

43

LTP LTP

Assessing surface parasitic forces on ground: the torsion pendulum

Test-mass

Firenze February 23, 2009

  • S. Vitale

44

Disturbing surroundings (GRS)

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SLIDE 12

2/24/2009 12

LTP LTP

Firenze February 23, 2009

  • S. Vitale

45

LTP LTP

Firenze February 23, 2009

  • S. Vitale

46 15

10 N

−

≤

LTP LTP

Work-function patches create stray voltages Couple to test-mass noisy charge and create force. Fluctuate over time

Firenze February 23, 2009

  • S. Vitale

47

0-force: stray voltage has been compensated Force per unit charge

  • r test-mass potential

LTP LTP

Firenze February 23, 2009

  • S. Vitale

48

slide-13
SLIDE 13

2/24/2009 13

LTP LTP 40 micron Silica Fiber Q=106

Firenze February 23, 2009

  • S. Vitale

49

LTP LTP

Firenze February 23, 2009

  • S. Vitale

50

LTP LTP

Firenze February 23, 2009

  • S. Vitale

51

LTP LTP

Firenze February 23, 2009

  • S. Vitale

52

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SLIDE 14

2/24/2009 14

LTP LTP

Firenze February 23, 2009

  • S. Vitale

53

LTP LTP

Firenze February 23, 2009

  • S. Vitale

54

LTP LTP

Firenze February 23, 2009

  • S. Vitale

55

LTP LTP

LISA Pathfinder

  • Take one spacecraft
  • Take one LISA

Doppler Link

Firenze February 23, 2009

  • S. Vitale

56

  • Squeeze it into the

spacecraft

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SLIDE 15

2/24/2009 15

LTP LTP

Firenze February 23, 2009

  • S. Vitale

57 Firenze February 23, 2009

  • S. Vitale

58

LTP LTP

Firenze February 23, 2009

  • S. Vitale

59

LTP LTP

Implement LISA Geodesic Link within a factor 10

Firenze February 23, 2009

  • S. Vitale

60

Find a route to project to LISA

Limited by features of test (extra forces, poorer environment)

slide-16
SLIDE 16

2/24/2009 16

LTP LTP

Pathfinder → LISA

  • Fly nominal LISA

hardware on Pathfinder:

– Maximize returns of the test – Shortens time to develop LISA

  • Identify quantitatively

leading sources of noise:

– Physical model allows extrapolation to LISA – Will allow accurate understanding of LISA data

Firenze February 23, 2009

  • S. Vitale

61

LTP LTP

Firenze February 23, 2009

  • S. Vitale

62

LTP LTP

Firenze February 23,

  • S. Vitale

63

Practicing routing and packaging LTP LTP

Gravitational balance

Firenze February 23,

  • S. Vitale

64

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SLIDE 17

2/24/2009 17

LTP LTP

Firenze February 23,

  • S. Vitale

65

LTP LTP

LISA Hardware

Firenze February 23, 2009

  • S. Vitale

66

LTP LTP

Firenze February 23, 2009

  • S. Vitale

67

LTP LTP

Firenze February 23, 2009 68

  • S. Vitale
slide-18
SLIDE 18

2/24/2009 18

LTP LTP 40 micron Silica Fiber Q=106

Firenze February 23, 2009

  • S. Vitale

69

LTP LTP 40 micron Silica Fiber Q=106

Firenze February 23, 2009

  • S. Vitale

70

LPF LTP LTP

Pathfinder interferometry and the relevance to LISA

Test- mass Spacecraft Test- mass Spacecraft

5×106 km

Firenze February 23, 2009

  • S. Vitale

71

  • LISA link is 3-stage
  • LISA pathfinder has no spacecraft → spacecraft link
  • A test of the local interferometric readout for LISA
  • A test of the test-mass → spacecraft → test-mass

split link

LTP LTP

Potential local LISA readout

Firenze February 23, 2009

  • S. Vitale

72

Albert Einstein Institute

slide-19
SLIDE 19

2/24/2009 19

LTP LTP

The test-mass ↔ spacecraft ↔ test- mass link

Firenze February 23, 2009

  • S. Vitale

73

Albert Einstein Institute LTP LTP

The link hardware: laser

Firenze February 23, 2009

  • S. Vitale

74

LTP LTP

The link hardware: optical bench

Firenze February 23, 2009 75

  • S. Vitale

LTP LTP

Also used as drag-free reference

Firenze February 23, 2009

  • S. Vitale

76

Albert Einstein Institute

slide-20
SLIDE 20

2/24/2009 20

LTP LTP

The link hardware: the ultra-stable structure

Firenze February 23, 2009

  • S. Vitale

77

LTP LTP

The link hardware: ultra-stable structure

Firenze February 23, 2009

  • S. Vitale

78

LISA Pathfinder

Overview of electrical models

DMU CCU LCU IS FEE (SAU & SSU) ULU BBR PMU BBR 1

LISA Pathfinder

LTP EM flat-bed set-up

LTP SCOE & OM SCOE EM Set-up 1

slide-21
SLIDE 21

2/24/2009 21

LTP LTP

Firenze February 23, 2009

  • S. Vitale

81

LTP LTP

Firenze February 23, 2009

  • S. Vitale

82

LTP LTP

Firenze February 23, 2009

  • S. Vitale

83

LTP LTP

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  • S. Vitale

84

slide-22
SLIDE 22

2/24/2009 22

One example: “spacecraft noise”

Firenze February 23,

  • S. Vitale

85

Things are not perfectly differential

S/C

TM TM

x Δ

  • S. Vitale

86 Firenze February 23, 2009

Things are not perfectly differential

S/C

TM TM SC2

x

  • SC1

x

  • S. Vitale

87

( )

SC2 SC1

x x 1 x Δ = + + δ

  • 2

1 SC1

x x x = − + δ×

Firenze February 23, 2009

  • U. Glasgow

Firenze February 23, 2009

  • S. Vitale

88 4

10− δ ≤

slide-23
SLIDE 23

2/24/2009 23

The effect of gradients

S/C

TM

  • S. Vitale

89 Firenze February 23, 2009

The effect of gradients

TM

S/C S/C

SC

x Δ

  • S. Vitale

90 2 1 1 SC

g x = ω

Firenze February 23, 2009

The effect of gradients

S/C

TM

  • S. Vitale

91

Spacecraft jitter accelerates test-mass via gradients

Firenze February 23, 2009

Correcting for Spacecraft Motion

  • Spacecraft motion is measured with high

resolution (interferometer)

  • Effect in differential link can be subtracted

Firenze February 23, 2009

  • S. Vitale

92

slide-24
SLIDE 24

2/24/2009 24

A simulated example

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  • S. Vitale

93

Uncorrected differential acceleration

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  • S. Vitale

94

Corrected for cross-talk and coupling

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  • S. Vitale

95

LTP LTP

Firenze February 23,

  • S. Vitale

96

slide-25
SLIDE 25

2/24/2009 25

Data analysis

ASCII Raw data Analysis Objects Raw data Analysis Objects Processed data

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97

LTP LTP

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98

Data analysis running during operation for quick re-planning

LTP LTP

Raising the stake

Firenze February 23, 2009

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99

LTP LTP

Firenze February 23,

  • S. Vitale

100