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LISA
LISAA Mission to detect and observe Gravitational Waves
O. Jennrich, ESA/ESTEC
on behalf of the LISA Science Team
LISA 2Réunion LISA-France, Collège de France, 20/21 Janvier 2005
What are Gravitational Waves?
Gravitational waves are predicted by GR (Einstein, 1915)
Propagate with the speed of light
Quadrupole waves, two polarisations
Bondi (1957): GW are physical, i.e. they carry energy, momentum and angular momentum
Small coupling to matter, hence almost no absorption or scattering in the Universe
Small amplitude, small effects
Ideal tool to observe
– distant objects
– centre of galaxies
– Black Holes
– early Universe
LISA 3Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Sources of GW
Any mass distribution that is accelerated in a non-spherical symmetric way (waving hands, running trains, planets in orbit,…)
Large masses necessary
– Neutron star binary system, Black Holes, …
LISA 4Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Hulse-Taylor Binary PSR1913+16
Einstein prediction
tP [s]
Observed loss of energy matches prediction of GW emission to betterthan 0.3%
Indirect evidence of gravitational waves
Outside any detector band
LISA 5Réunion LISA-France, Collège de France, 20/21 Janvier 2005
The Effect of a Gravitational Wave
GW change the distance between free-falling test masses
LISA 6Réunion LISA-France, Collège de France, 20/21 Janvier 2005
What are the sources?
‘ Useful’ frequency range stretches over 8 decades Asymmetrical collapse of a supernova core Coalescence of compact binary systems (NS-NS, NS-BH) Inspiralling white dwarf binaries Compact binaries (early evolution) BH formation, BH-BH coalescence, BH binaries Ground based detectors observe in the audio band Only a space borne detector can overcome the seismic barrier
LISA 7Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA Verification Binaries
0.60.794U1626-67
600.105CC ComW Uma
23.04U1820-30LMXB
Strain h (10-23)
f (mHz)
SourceClass
1000.24KPD 1930+2752
600.26KPD 0422+4521WD+sdB
> 200.14WD 2331+290
400.14WD 1704+481
200.16WD 1101+364
400.38WD 0957-666WD+WD
Strain h (10-23)
f (mHz)
SourceClass
30.72GP Com
41.16CP Eri
101.24V803 Cen
101.36CR Boo
201.79HP Lib
201.94AM CVn
93.2KUV05184-0939
603.5RXJ1914+245
406.2RXJ0806.3+1527AM CVn
Galactic binaries (100pc – 1000pc)
Instrument verfication sources
Guranteed detection!
0.60.794U1626-67
600.105CC ComW Uma
23.04U1820-30LMXB
Strain h (10-23)
f (mHz)
SourceClass
1000.24KPD 1930+2752
600.26KPD 0422+4521WD+sdB
> 200.14WD 2331+290
400.14WD 1704+481
200.16WD 1101+364
400.38WD 0957-666WD+WD
Strain h (10-23)
f (mHz)
SourceClass
30.72GP Com
41.16CP Eri
101.24V803 Cen
101.36CR Boo
201.79HP Lib
201.94AM CVn
93.2KUV05184-0939
603.5RXJ1914+245
406.2RXJ0806.3+1527AM CVn
LISA 8Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA Verification Binaries
LISA 9Réunion LISA-France, Collège de France, 20/21 Janvier 2005
At the Edge of a Black Hole
Capture by Massive Black Holes– By observing 10,000 or more orbits of a compact object as it
inspirals into a massive black hole (MBH), LISA can map with superb precision the space-time geometry near the black hole
– Allows tests of many predictions of General Relativity including the “no hair” theorem
LISA 10Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Evidence for Black Holes
Stellar motions in the vicinity of Sgr A*.
The orbital accelerations of stars close to the Galactic centre allow placing constraints on the position and mass of the central supermassive black hole
LISA 11Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Mergers of Massive Black Holes
Massive black hole binaries produce gravitational waves in all phases of their evolution
Signal-to-noise of 1000 or more allows LISA to perform precision tests of General Relativity at ultra-high field strengths
LISA 12Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Evidence for (S)MBH binaries
During the collision of Galaxies MBH will interact
After merging, MBH binaries can exist
LISA 25Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Evolution of (S)MBH binaries
B Schutz (AEI)
LISA 26Réunion LISA-France, Collège de France, 20/21 Janvier 2005
GW from SMBH
Time series of the GW amplitude
h
h+
-10-22
0
1022
-10-22
0
1022
S Hughes (CalTech)
LISA 27Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA Science Goals Merging supermassive black
holes
Merging intermediate-mass/seed black holes
Gravitational captures
Galactic and verification binaries
Cosmological backgrounds and bursts
Determine the role of massive black holes in galaxy evolution
Make precision tests of Einstein’s Theory of Relativity
Determine the population of ultra-compact binaries in the Galaxy
Probe the physics of the early universe
NASA/CXC/MPE/S. Komossa et al.K. Thorne (Caltech) NASA, Beyond Einstein
LISA 28Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA Mission Concept
Cluster of 3 spacecraft in a heliocentric orbit
Trailing the Earth by 20° (50 Million kilometer)
Equilateral triangle with 5 Million kilometer arm length
Inclined with respect to the ecliptic by 60°
LISA 29Réunion LISA-France, Collège de France, 20/21 Janvier 2005
The LISA Orbit
Constellation counter-rotates during the course of one year
LISA 30Réunion LISA-France, Collège de France, 20/21 Janvier 2005
The LISA Orbit
LISA 31Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA layout
main transpondedlaser beams
referencelaser beams
Diffraction widens the laser beam
to many kilometers
– 0.7 W sent, 70 pW received
LISA 32Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA optical scheme “one-way” measurements
– Each received laser is individually recombined with a local laser
– Phasemeasurement occurs locally
Additional measure-ments on the back-side of the proof masses
LISA 33Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA layout
main transpondedlaser beams
referencelaser beams
Diffraction widens the laser beam
to many kilometers
– 0.7 W sent, 70 pW received
Michelson with a 3rd arm, Sagnac
Capable to distinguish both
polarizations of a GW
Orbital movement
provides
directionality
LISA 34Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Using phase modulation due to orbital motion is equivalent to aperture synthesis
Gives diffraction limit = / 1 AU
Measurements on detected sources:
- ~ 1’ – 1o - (mass,distance) 1%
Wave(f = 16 mHz)
Angular Resolution with LISA
LISA 35Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA layout
main transpondedlaser beams
referencelaser beams
Diffraction widens the laser beam to many kilometers
– 0.7 W sent, 70 pW received
Michelson with a 3rd arm, Sagnac
Capable to distinguish bothpolarizations of a GW
Orbital movement providesdirectionality
Laser beams reflected off free-flying test masses
LISA 36Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 37Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 38Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 39Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 40Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 41Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 42Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 43Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 44Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 45Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 46Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 47Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 48Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 49Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
LISA 50Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Ensuring free-fall
“Drag-free” control 10-15 m/(s2 Hz)
– Not truly “drag-free”, hence named DRS
Needs tight control of
– Magnetic cleanliness
– Electro-static noise (patch field effect, charging, …)
– Gravity gradient
Ground tests can only demonstrate 10-13 m/(s2 Hz)
LISA PF as technology demonstrator
LISA 54Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA layout
LISA 55Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Spacecraft Layout
LISA 56Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Spacecraft Layout
LISA 57Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Spacecraft Layout
LISA 58Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Payload layout
LISA 59Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Optical layout
LISA 60Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA Interferometry
Each beam (reference and main) is separately heterodyned with the local laser on a photodiode
– 12 signals: 6 from the main beams plus 6 from the reference beams
– Beat signals from the reference beams are used to phase-lock the lasers in the same spacecraft
Armlength changes slowly over a range of several 1000 km per year due to orbital mechanics
– Fringe rate of several MHz makes interferometer self calibrating based on laser wavelength
– No calibration procedure necessary during operation
– Need Ultrastable Oscillator to remove Doppler shift before transmission to the ground
– USO transmitted as laser sideband (~2 GHz) to be stabilised on armlength
main beams
reference beams
LISA 61Réunion LISA-France, Collège de France, 20/21 Janvier 2005
18 beat signals:
– 6 beat signals from main beams
– 6 beat signals from reference beams
– 6 beat signals from USO sideband signals
Linear combinations of signals
– Cancel laser and USO noise and keep instrumental noise and the GW
signal
– Cancel the GW signal and laser and USO noise and keeps the
instrumental noise
LISA can distinguish a stochastic gravitational wave
background from instrumental noise
LISA Interferometry
main beams
reference beams
LISA 62Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Instrumental Noise
Armlength penalty:
5 Million kilometer
Acceleration noise: 10-15 m/(s2 Hz)
Quality of drag-free control,
gravity gradient noise
Shot noise: 70 pW 10-5 cycles/Hz
LISA 63Réunion LISA-France, Collège de France, 20/21 Janvier 2005
LISA Launch and Cruise Delta IV launches all three spacecraft Each spacecraft is attached to its own propulsion
module– Propulsion Module V = 1.22 km/sec
– Propulsion module incorporates a bipropellent (N2
O4 / hydrazine) system and a Reaction Control System for attitude control
13 month cruise phase
LISA 64Réunion LISA-France, Collège de France, 20/21 Janvier 2005
Status of LISA today
Proposed to ESA 1993, approved as a Cornerstone Mission 1996
Collaborative ESA/NASA mission with a 50/50 sharing ratio
– ESA: Responsibility for the payload I&T, 50% of the payload (nationally
funded)
– NASA: 3 S/C, launcher, ground segment (DSN), mission ops
– Science ops will be shared
– Data analysis by two independent teams (Europe and US)
Launch foreseen in the 2012/2013 timeframe
LISA PF in 2008
– Approved by ESA’s SPC in June 04 (160 M€)
– Europe: LISA Technology Package (LTP)
– US: Disturbance Reduction System (DRS)
LISA 65Réunion LISA-France, Collège de France, 20/21 Janvier 2005