lisa 1 lisa/gaia/ska birmingham. lisa a mission to detect and observe gravitational waves o....

LISA 1LISA/GAIA/SKA Birmingham

LISA

LISAA Mission to detect and observe Gravitational Waves

O. Jennrich, ESA/ESTEC

LISA Project Scientist


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


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, …


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


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 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 Verification Binaries

4U1820-30


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


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


Evidence for (S)MBH binaries

During the collision of Galaxies MBH will interact

After merging, MBH binaries can exist


Evolution of (S)MBH binaries


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 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



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




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




Equilateral triangle with 5 million kilometers arm length

Inclined with respect to the ecliptic by 60°

– Required by orbital mechanics


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 optical scheme


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


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


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


Payload layout


Optical layout


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


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


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

lisa 1 lisa/gaia/ska birmingham. lisa a mission to detect and observe gravitational waves o....

Documents

lisagaiaska birmingham

detector sensitivity

hair theorem slide

seismic barrier slide

massive black hole mbh

black hole capture

bhbh coalescence

evolution signal