Introduction to HYPER Measuring Lense-Thirring with Atom Interferometry P. BOUYER Laboratoire Charles Fabry de l’Institut d’Optique Orsay, France

ESTEC, March 6th 2 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

ESTEC, March 6th 3 The Lense-Thirring Effect  General relativistic effect  Gravitomagnetism  Curvature of space-time around massive rotating bodies Courtesy of Astrium

ESTEC, March 6th 4 The Lense-Thirring Effect  General relativistic effect  gravitomagnetism  Curvature of space-time around massive rotating bodies  Strong effect near black holes  Precession and twist of acretion disks Images from Center for Theoretical Astrophysics University of Illinois at Urbana-Champaign

ESTEC, March 6th 5 The Lense-Thirring Effect  General relativistic effect  gravitomagnetism  Curvature of space-time around massive rotating bodies  Strong effect near black holes  Precession and twist of acretion disks  Small effect close to earth  Possible to measure average frame dragging –LAGEOS –GP-B

ESTEC, March 6th 6 The Lense-Thirring Effect  General relativistic effect  gravitomagnetism  Curvature of space-time around massive rotating bodies  Strong effect near black holes  Precession and twist of acretion disks  Small effect close to earth  Possible to measure average frame dragging –LAGEOS –GP-B  Mapping Lense-Thirring –HYPER

ESTEC, March 6th 7 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

ESTEC, March 6th 8 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 3x rad/s -3x rad/s

ESTEC, March 6th 9 The HYPER mission configuration MISSION DRIVERS & CONSTRAINTS  Low-Earth Orbit (for mapping the Lense-Thirring effect)  Extremely demanding pointing accuracy  Relative Pointing Error: radians (2 marcsec) over 3 sec  Stable relative pointing between PST and ASU  Drag-free environment  g residual accelerations  Precise control of gravity gradients   The Lense-Thirring effect   Maximum about rad/s – –1 year integration – –High accuracy of rotation measurement

ESTEC, March 6th 10 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

ESTEC, March 6th 11 ASU1 ASU2 Precision Star Tracker Pointing Cold Atom Source ASU Reference (connected to the Raman Lasers & to the Star Tracker) The HYPER Payload

ESTEC, March 6th 12 ASU1 ASU2 Precision Star Tracker Raman Lasers Module Laser Cooling Module   Expected Overall Performance:   3x rad/s over one year of integration i.e. a S/N~10 at twice the orbital frequency ASU Resolution : 3x rad/s /  Hz Payload components

ESTEC, March 6th 13 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

ESTEC, March 6th 14 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 Time

ESTEC, March 6th 15 Manipulating atoms with light  Controlling the interfaction time controls the result of the oscillation  Half way between red and blue –  /2 pulse Time

ESTEC, March 6th 16 Manipulating atoms with light  Controlling the interfaction time controls the result of the oscillation  Half way between red and blue –  /2 pulse  Another half : all the way from red to blue –  pulse Time

ESTEC, March 6th 17 Manipulating atoms with light  Controlling the interfaction time controls the result of the oscillation  Half way between red and blue –  /2 pulse  Another half : all the way from red to blue –  pulse  The other way : from blue to red –  pulse Time

ESTEC, March 6th 18 Manipulating atoms with light  The  /2 pulse is a beam splitter  Half way between red and blue  Coherent superposition of red and blue

ESTEC, March 6th 19 Manipulating atoms with light  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

ESTEC, March 6th 20 The Atom Interferometer  The first  /2 pulse - beam splitter  Creates the coherent superposition

ESTEC, March 6th 21 The Atom Interferometer  The first  /2 pulse - beam splitter  Creates the coherent superposition  The two parts of the atom separate  Splitting between the two parts

ESTEC, March 6th 22 The Atom Interferometer  The first  /2 pulse - beam splitter  Creates the coherent superposition  The two parts of the atom separate  Splitting between the two parts  Apply the  pulse - mirror  Changes blue to red –Velocity from 0 to recoil  Changes red to blue –Velocity from recoil to 0

ESTEC, March 6th 23 The Atom Interferometer  The first  /2 pulse - beam splitter  Creates the coherent superposition  The two parts of the atom separate  Splitting between the two parts  Apply the  pulse - mirror  Changes blue to red –Velocity from 0 to recoil  Changes red to blue –Velocity from recoil to 0  Apply last  /2 pulse when the two parts overlap again

ESTEC, March 6th 24 The Atom Interferometer  The first  /2 pulse - beam splitter  Creates the coherent superposition  The two parts of the atom separate  Splitting between the two parts  Apply the  pulse - mirror  Changes blue to red –Velocity from 0 to recoil  Changes red to blue –Velocity from recoil to 0  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

ESTEC, March 6th 25 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 e ikx

ESTEC, March 6th 26 The atom «reads» the phase of the laser  Each time the atom changes state, the laser imprints its phase on the atom 0 1111

ESTEC, March 6th 27 The atom «reads» the phase of the laser  Each time the atom changes state, the laser imprints its phase on the atom 0 1111

ESTEC, March 6th 28 The atom «reads» the phase of the laser  Each time the atom changes state, the laser imprints its phase on the atom 0 1111  2l  2r

ESTEC, March 6th 29 The atom «reads» the phase of the laser  Each time the atom changes state, the laser imprints its phase on the atom 0 1111  2l  2r

ESTEC, March 6th 30 The atom «reads» the phase of the laser  Each time the atom changes state, the laser imprints its phase on the atom 0 1111  2l  2r 0  3 Final phase difference (  1  2r  2l  3 

ESTEC, March 6th 31 Phase shift comes from acceleration 0 1111  2l  2r 0  3 Final phase difference (  1  2r  2l  3 

ESTEC, March 6th 32 The atomic sagnac unit  3 separated diffraction zones  Corriolis acceleration comes from rotating laser

ESTEC, March 6th 33 The atomic sagnac unit  3 separated diffraction zones  Corriolis acceleration comes from rotating laser  Rotation and acceleration signal are mixed  Need dual ASU for real rotation measurement a a

ESTEC, March 6th 34 Interferometer length 60 cm Atom velocity 20 cm/s Drift time 3 s 10 9 atoms/shot Sensitivity 3x rad/s The atomic sagnac unit

ESTEC, March 6th 35 MISSION DRIVERS & CONSTRAINTS   Typical measurement time : 3 sec   Typical rotation sensitivity of ASU : rad/s (1 sec)   Signal detection : 2.2x rad/s half orbit   ASU measures lasers rotations/vibrations   Low-Earth Orbit (for mapping the Lense-Thirring effect)   Extremely demanding pointing accuracy   Relative Pointing Error: radians (2 marcsec) over 3 sec   Stable relative pointing between PST and ASU about 1 arcsec   Drag-free environment   g residual accelerations   Precise control of gravity gradients – –Knowledge and/or control to better than g/m

ESTEC, March 6th 36 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

ESTEC, March 6th 37 HYPER and future space missions  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

ESTEC, March 6th 38 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

ESTEC, March 6th 39 Stanford laboratory gravimeter g Courtesy of S. Chu, Stanford

ESTEC, March 6th 40 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/Hz 1/2 (2.8x10 -9 g/Hz 1/2 per accelerometer) Atoms L a s e r B e a m Courtesy of M. Kasevich, Stanford

ESTEC, March 6th 41 Stanford/Yale laboratory gyroscope AI gyroscope, demonstrated laboratory performance: 2x10 -6 deg/hr 1/2 ARW < deg/hr bias stability 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

ESTEC, March 6th 42 Agenda Introduction to Lense-Thirring Effect Key requirements for the HYPER mission The Payload : Atomic Sagnac Unit Atom Inertial sensors : How does-it work ? Early earth-based Atom Inertial sensors HYPER and future space missions Ongoing earth based projects

ESTEC, March 6th 43 Cold Atom Inertial Base (Paris) Courtesy of A. Landragin (Paris) Theoretical model (include. relativity) by C. Bordé

ESTEC, March 6th 44 CASI : Cold Atom Sagnac Interferometer (Hannover) Rubidium-87 launch velocities:  1 m/s enclosed area A  0.2 cm 2 expected sensitivity:   rad/s  Hz -1 Courtesy of E. Rasel (Hannover))

ESTEC, March 6th 45 Courtesy of G. Tino (Fireze)

ESTEC, March 6th 46 Interferometry with Coherent Ensemble (Paris)   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)