LISA
LISAA Mission to detect and observe Gravitational Waves
O. Jennrich, ESA/ESTEC
LISA Project Scientist
LISA 3LISA/GAIA/SKA Birmingham
What are Gravitational Waves?
Gravitational waves are predicted by GR (Einstein, 1915)
Propagate with the speed of light
Change the distance between freely falling test masses
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 4LISA/GAIA/SKA Birmingham
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 5LISA/GAIA/SKA Birmingham
Hulse-Taylor Binary PSR1913+16
Observed loss of energy matches prediction of GW emission to (0.13 ± 0.21)%
Indirect evidence of gravitational waves
Frequency 70 μHz, amplitude 7×10-23
outside detector sensitivity
LISA 6LISA/GAIA/SKA Birmingham
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 7LISA/GAIA/SKA Birmingham
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!
LMXB 4U1820-30 3.0 2
LISA 9LISA/GAIA/SKA Birmingham
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 11LISA/GAIA/SKA Birmingham
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 12LISA/GAIA/SKA Birmingham
Evidence for (S)MBH binaries
During the collision of Galaxies MBH will interact
After merging, MBH binaries can exist
LISA 25LISA/GAIA/SKA Birmingham
Summary of LISA Science Goals Merging supermassive
black holes
Merging intermediate-mass/seed black holes
Gravitational captures
Galactic and verification binaries
Cosmological backgrounds and bursts
NASA/CXC/MPE/S. Komossa et al.K. Thorne (Caltech) NASA, Beyond Einstein
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
LISA 26LISA/GAIA/SKA Birmingham
LISA Mission Concept Cluster of 3 spacecraft in a heliocentric orbit
– Spacecraft shield the test masses from external forces (solar wind, radiation pressure)
– Allows measurement of amplitude and polarisation of GW
LISA 27LISA/GAIA/SKA Birmingham
LISA Mission Concept Cluster of 3 spacecraft in a heliocentric orbit
Trailing the Earth by 20° (50 million kilometers)
– Reducing the influence of the Earth-Moon system on the orbits
– Keeping the communication requirements (relatively) standard
LISA 28LISA/GAIA/SKA Birmingham
LISA Mission Concept Cluster of 3 spacecraft in a heliocentric orbit
Trailing the Earth by 20° (50 million kilometers)
Equilateral triangle with 5 million kilometers arm length
– Results in easily measurable pathlength variations
– Orbit is still stable enough to allow for mission duration >5years
LISA 29LISA/GAIA/SKA Birmingham
LISA Mission Concept Cluster of 3 spacecraft in a heliocentric orbit
Trailing the Earth by 20° (50 million kilometers)
Equilateral triangle with 5 million kilometers arm length
Inclined with respect to the ecliptic by 60°
– Required by orbital mechanics
LISA 30LISA/GAIA/SKA Birmingham
The LISA Orbit Constellation counter-rotates during the course of one
year
Phase modulation (Doppler) and amplitude modulation (antenna pattern) give directionality
– Synthetic aperture diffraction limit: = / 1 AU
– Measurements on detected sources:
~ 1’ – 1°, (mass,distance) 1%
LISA 32LISA/GAIA/SKA Birmingham
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 as common clock
– USO transmitted as laser sideband (~2 GHz) serve as common clock
main beams
reference beams
LISA 33LISA/GAIA/SKA Birmingham
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 34LISA/GAIA/SKA Birmingham
Instrumental Noise
Armlength penalty:
5 Million kilometer
Acceleration noise: 3×10-15 m/(s2 Hz)
Quality of drag-free control,
gravity gradient noise
Shot noise: 70 pW 10-5 cycles/Hz
LISA 37LISA/GAIA/SKA Birmingham
LISA Launch and Cruise Atlas V launches all three spacecraft Each spacecraft is attached to its own propulsion
module– Propulsion Module V = 2.9 km/sec
– Propulsion module incorporates a bipropellent (N2
O4 / hydrazine) system and a Reaction Control System for attitude control
13 month cruise phase
LISA 38LISA/GAIA/SKA Birmingham
Status of LISA today
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) – TBC
– Preparation for data analysis have just started – Mock LISA Data Challenge
Launch foreseen in the 2015 timeframe
LISA PF in 2009
– Approved by ESA’s SPC in June 04 (160 M€)
– Europe: LISA Technology Package (LTP)
– US: Disturbance Reduction System (DRS)
– Recent descoping – AOCS and thrusters only
LISA 39LISA/GAIA/SKA Birmingham
Status of LISA
Recent developments in ESA and NASA
– ESA’s SPC demanded review of the programmatic situation in 2008
– Affects LISA and Solar Orbiter
– Boundary conditions are not yet set
– NASA’s budget request for FY 2007 has start of the development of LISA ‘indefinitely deferred’
– But: technology and science studies are ongoing
– Selection of one of LISA, ConX, JDEM ‘later this decade’, (2008?)
– Project works on somewhat reduced funding in the US, limited effects on the ESA formulation study phase
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