1. LISA 1 LISA/GAIA/SKA Birmingham

2. LISA A Mission to detect and observe Gravitational Waves O. Jennrich, ESA/ESTEC LISA Project Scientist

3. LISA 3 LISA/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

4. LISA 4 LISA/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, …

5. LISA 5 LISA/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

6. LISA 6 LISA/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

7. LISA 7 LISA/GAIA/SKA Birmingham LISA Verification Binaries  Galactic binaries (100pc – 1000pc)  Instrument verfication sources  Guranteed detection! LMXB 4U1820-30 3.0 2

8. LISA 8 LISA/GAIA/SKA Birmingham LISA Verification Binaries 4U1820-30

9. LISA 9 LISA/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

10. LISA 10 LISA/GAIA/SKA Birmingham Evidence for Super Massive 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

11. LISA 11 LISA/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

12. LISA 12 LISA/GAIA/SKA Birmingham Evidence for (S)MBH binaries  During the collision of Galaxies MBH will interact  After merging, MBH binaries can exist

13. LISA 13 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

14. LISA 14 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

15. LISA 15 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

16. LISA 16 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

17. LISA 17 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

18. LISA 18 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

19. LISA 19 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

20. LISA 20 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

21. LISA 21 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

22. LISA 22 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

23. LISA 23 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

24. LISA 24 LISA/GAIA/SKA Birmingham Evolution of (S)MBH binaries

25. LISA 25 LISA/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

26. LISA 26 LISA/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

27. LISA 27 LISA/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

28. LISA 28 LISA/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

29. LISA 29 LISA/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

30. LISA 30 LISA/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%

31. LISA 31 LISA/GAIA/SKA Birmingham LISA optical scheme

32. LISA 32 LISA/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

33. LISA 33 LISA/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

34. LISA 34 LISA/GAIA/SKA Birmingham Instrumental Noise Armlength penalty: 5 Million kilometer Acceleration noise: 3×10 -15 m/(s 2  Hz) Quality of drag-free control, gravity gradient noise Shot noise: 70 pW  10 -5 cycles/  Hz

35. LISA 35 LISA/GAIA/SKA Birmingham Payload layout

36. LISA 36 LISA/GAIA/SKA Birmingham Optical layout

37. LISA 37 LISA/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 (N 2 O 4 / hydrazine) system and a Reaction Control System for attitude control  13 month cruise phase

38. LISA 38 LISA/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

39. LISA 39 LISA/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

40. LISA 40 LISA/GAIA/SKA Birmingham