Introduction to HYPER Measuring Lense-Thirring with Atom Interferometry P. BOUYER Laboratoire...

Introduction to HYPERMeasuring Lense-Thirring with Atom Interferometry

P. BOUYER

Laboratoire Charles Fabry de l’Institut

d’Optique

Orsay, France

2 ESTEC, March 6th

Agenda

Introduction to Lense-Thirring Effect

Key requirements for the HYPER mission

The Payload : Atomic Sagnac Unit

Atom Inertial sensors : How does-it work ?

HYPER and future space missions

Early earth-based Atom Inertial sensors

Ongoing earth based projects

3 ESTEC, March 6th

The Lense-Thirring Effect

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General relativistic effect Gravitomagnetism

Curvature of space-time around massive rotating bodies

Courtesy of Astrium

4 ESTEC, March 6th


General relativistic effect gravitomagnetism


Strong effect near black holes Precession and twist of

acretion disks

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Images from Center for Theoretical Astrophysics University of Illinois at Urbana-Champaign

5 ESTEC, March 6th





acretion disks

Small effect close to earth Possible to measure

average frame dragging

– LAGEOS

– GP-B

6 ESTEC, March 6th





acretion disks

Small effect close to earth Possible to measure

average frame dragging– LAGEOS

– GP-B

Mapping Lense-Thirring– HYPER

7 ESTEC, March 6th

Agenda








8 ESTEC, March 6th

The HYPER mission configuration

The Lense-Thirring effect The periodic cycle is

half the orbit period

– 2 ASU in quadrature

Geodetic de Sitter 40 to 80 times bigger

Constant for circular orbit

3x10-14 rad/s

-3x10-14 rad/s

9 ESTEC, March 6th

The HYPER mission configuration

MISSION DRIVERS & CONSTRAINTS Low-Earth Orbit (for mapping the Lense-Thirring effect)

Extremely demanding pointing accuracy Relative Pointing Error: 10-8 radians (2 marcsec) over 3 sec

Stable relative pointing between PST and ASU

Drag-free environment 10 -9 g residual accelerations

Precise control of gravity gradients

The Lense-Thirring effect Maximum about 10-14 rad/s

– 1 year integration

– High accuracy of rotation measurement

10 ESTEC, March 6th

Agenda








11 ESTEC, March 6th

ASU1

ASU2Precision Star Tracker Pointing

Cold Atom Source

ASU Reference (connected to the Raman Lasers

& to the Star Tracker)

The HYPER Payload

12 ESTEC, March 6th

ASU1

ASU2

Precision Star Tracker

Raman Lasers Module

Laser Cooling Module

Expected Overall Performance:

3x10-15rad/s over one year of

integration i.e. a S/N~10 at twice

the orbital frequency

ASU Resolution: 3x10-11rad/s /Hz

Payload components

13 ESTEC, March 6th

Agenda








14 ESTEC, March 6th

Manipulating atoms with light

Atom Interferometry uses laser induced resonance oscillation

Atoms with 2 different states (red/blue) with different energy

Laser with frequency equal to energy difference

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Time

15 ESTEC, March 6th


Controlling the interfaction time controls the result of the oscillation

Half way between red and blue

– /2 pulse

Time

16 ESTEC, March 6th




– /2 pulse

Another half : all the way from red to blue

– pulse

Time

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– /2 pulse

Another half : all the way from red to blue

– pulse

The other way : from blue to red

– pulse

Time

18 ESTEC, March 6th


The /2 pulse is a beam splitter Half way between red and blue

Coherent superposition of red and blue

19 ESTEC, March 6th


The /2 pulse is a beam splitter Half way between red and blue

Coherent superposition of red and blue

The red and blue states correspond to different kinetic energies

Velocities along laser direction

Blue : excited state

– Photon absorbed from laser

– Photon momenum transferred to atom

– Recoil velocity ≈1cm/s

Red : «ground» state

– No photon absorbed

– No velocity


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The Atom Interferometer

The first /2 pulse - beam splitter Creates the coherent

superposition


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superposition

The two parts of the atom separate Splitting between the two parts


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superposition


Apply the pulse - mirror Changes blue to red

– Velocity from 0 to recoil

Changes red to blue

– Velocity from recoil to 0


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superposition




Changes red to blue


Apply last /2 pulse when the two parts overlap again


24 ESTEC, March 6th



superposition




Changes red to blue


Apply last /2 pulse when the two parts overlap again

Red or Blue output depend of phase difference between two path


phase difference

Atomic State


25 ESTEC, March 6th

The atom «reads» the phase of the laser

Each time the atom changes state, the laser imprints its phase on the atom


«Stationary» Laser Phase eikx«Stationary» Laser Phase eikx«Stationary» Laser Phase eikx«Stationary» Laser Phase eikx«Stationary» Laser Phase eikx

26 ESTEC, March 6th



00 11

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00 11


28 ESTEC, March 6th



00 11

2l2l 2r2r

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00 11

2l2l 2r2r


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00 11

2l2l 2r2r

0033 Final phase differenceFinal phase difference ( (1 1 2r2r2l 2l 33

Final phase differenceFinal phase difference ( (1 1 2r2r2l 2l 33

31 ESTEC, March 6th


Phase shift comes from acceleration

00 11

2l2l 2r2r

0033 Final phase differenceFinal phase difference ( (1 1 2r2r2l 2l 33

Final phase differenceFinal phase difference ( (1 1 2r2r2l 2l 33

32 ESTEC, March 6th

The atomic sagnac unit

3 separated diffraction zones

Corriolis acceleration comes from rotating laser


⋅=Φ Ah

m22 at

rot ΩL

t2

v

vL= Ω

33 ESTEC, March 6th


3 separated diffraction zones

Corriolis acceleration comes from rotating laser

Rotation and acceleration signal are mixed

Need dual ASU for real rotation measurement

⋅=Φ Ah

m22 at

rot ΩL

t2

v

vL=

2L

2

v

Lkacc =Φ 2driftT ⋅ = ⋅a a

Ω QuickTime™ et undécompresseur Photo - JPEGsont requis pour visionner cette image.

34 ESTEC, March 6th

Interferometer length 60 cm

Atom velocity 20 cm/s

Drift time 3 s

109 atoms/shot

Sensitivity 3x10-11 rad/s


35 ESTEC, March 6th

MISSION DRIVERS & CONSTRAINTS

Typical measurement time : 3 sec

Typical rotation sensitivity of ASU : 10-11 rad/s (1 sec) Signal detection : 2.2x10-15 rad/s rms @ half orbit

ASU measures lasers rotations/vibrations

Low-Earth Orbit (for mapping the Lense-Thirring effect)

Extremely demanding pointing accuracy

Relative Pointing Error: 10-8 radians (2 marcsec) over 3 sec

Stable relative pointing between PST and ASU about 1 arcsec

Drag-free environment

10-9 g residual accelerations

Precise control of gravity gradients – Knowledge and/or control to better than 10-10 g/m

36 ESTEC, March 6th

Agenda








37 ESTEC, March 6th


HYPER can benefit from TD of other missions PHARAO/ACES

– Laser Cooling Benches

– Radiofrequency chains

LISA/SMART-2/GOCE/MICROSCOPE

– Drag Free

– Accelerometers

LAGEOS/GOCE/MICROSCOPE

– AOCS (low orbit)

GP-B

– Precision Star Tracker (HYPER more demanding)

– Also from LISA

38 ESTEC, March 6th

Agenda








39 ESTEC, March 6th

Stanford laboratory gravimeter

10-8 g

Courtesy of S. Chu, Stanford

40 ESTEC, March 6th

Stanford/Yale laboratory gravity gradiometer

1.4 m

Distinguish gravity induced accelerations from those due to platform motion with differential acceleration measurements.

Demonstrated diffential acceleration sensitivity:

4x10-9 g/Hz1/2

(2.8x10-9 g/Hz1/2 per accelerometer)

Atoms

Atoms

L a s

e r

B

e a

m

Courtesy of M. Kasevich, Stanford

41 ESTEC, March 6th

Stanford/Yale laboratory gyroscope

AI gyroscope, demonstrated laboratory performance:

2x10-6 deg/hr1/2 ARW

< 10-4 deg/hr bias stability

Rotation rate (x10-5) rad/sec

-10 -5 0 5 10 15 20

Normalized signal

-1

0

1

Rotation signal

Bias stability

Compact, fieldable (navigation) and dedicated very high-sensitivity (Earth rotation dynamics, tests of GR) geometries possible.

Courtesy of M. Kasevich, Stanford

42 ESTEC, March 6th

Agenda








43 ESTEC, March 6th

Cold Atom Inertial Base (Paris)

Courtesy of A. Landragin (Paris)

Theoretical model (include. relativity) by C. Bordé

44 ESTEC, March 6th

CASI : Cold Atom Sagnac Interferometer (Hannover)

Rubidium-87

launch velocities: 1 m/s

enclosed area A 0.2 cm2

expected sensitivity: Ω 10-8-10-9 rad/sHz-1

Courtesy of E. Rasel (Hannover))

45 ESTEC, March 6th

Courtesy of G. Tino (Fireze)

46 ESTEC, March 6th

Interferometry with Coherent Ensemble (Paris)

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ONERA-SYRTE-IOTA-CNES project

Explore Best coherent source configuration for space

Study coherence properties of degenerate source of atoms

Interferometry with coherent sources

Courtesy of P. Bouyer (Paris)

Introduction to HYPER Measuring Lense-Thirring with Atom Interferometry P. BOUYER Laboratoire...

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