2. LISA A Mission to detect and observe Gravitational Waves O. Jennrich, ESA/ESTEC on behalf of the LISA Science Team

3. LISA 2 Réunion 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

4. LISA 3 Réunion 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, …

5. LISA 4 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Hulse-Taylor Binary PSR1913+16 Einstein prediction t P [s] Observed loss of energy matches prediction of GW emission to better than 0.3% Indirect evidence of gravitational waves Outside any detector band

6. LISA 5 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 The Effect of a Gravitational Wave GW change the distance between free-falling test masses

7. LISA 6 Réunion 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

8. LISA 7 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 LISA Verification Binaries Galactic binaries (100pc – 1000pc) Instrument verfication sources Guranteed detection!

9. LISA 8 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 LISA Verification Binaries

10. LISA 9 Réunion 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

11. LISA 10 Réunion 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

12. LISA 11 Réunion 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

13. LISA 12 Réunion 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

14. LISA 13 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

15. LISA 14 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

16. LISA 15 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

17. LISA 16 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

18. LISA 17 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

19. LISA 18 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

20. LISA 19 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

21. LISA 20 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

22. LISA 21 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

23. LISA 22 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

24. LISA 23 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

25. LISA 24 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries

26. LISA 25 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Evolution of (S)MBH binaries B Schutz (AEI)

27. LISA 26 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 GW from SMBH Time series of the GW amplitude h h+h+ -10 -22 0 10 22 -10 -22 0 10 22 S Hughes (CalTech)

28. LISA 27 Réunion 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 Einsteins 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

29. LISA 28 Réunion 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°

30. LISA 29 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 The LISA Orbit Constellation counter-rotates during the course of one year

31. LISA 30 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 The LISA Orbit

32. LISA 31 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 LISA layout main transponded laser beams reference laser beams Diffraction widens the laser beam to many kilometers – 0.7 W sent, 70 pW received

33. LISA 32 Réunion 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

34. LISA 33 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 LISA layout main transponded laser beams reference laser beams Diffraction widens the laser beam to many kilometers – 0.7 W sent, 70 pW received Michelson with a 3 rd arm, Sagnac Capable to distinguish both polarizations of a GW Orbital movement provides directionality

35. LISA 34 Réunion 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 – 1 o - (mass,distance) 1% Wave (f = 16 mHz) Angular Resolution with LISA

36. LISA 35 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 LISA layout main transponded laser beams reference laser beams Diffraction widens the laser beam to many kilometers – 0.7 W sent, 70 pW received Michelson with a 3 rd arm, Sagnac Capable to distinguish both polarizations of a GW Orbital movement provides directionality Laser beams reflected off free-flying test masses

37. LISA 36 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

38. LISA 37 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

39. LISA 38 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

40. LISA 39 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

41. LISA 40 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

42. LISA 41 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

43. LISA 42 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

44. LISA 43 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

45. LISA 44 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

46. LISA 45 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

47. LISA 46 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

48. LISA 47 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

49. LISA 48 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

50. LISA 49 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall

51. LISA 50 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Ensuring free-fall Drag-free control 10 -15 m/(s 2 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/(s 2 Hz) LISA PF as technology demonstrator

52. LISA 51 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 LPF mission goals Demonstrate free-fall quality to 10 -14 m/(s 2 Hz) Demonstrate feasibility of performing laser interferometry as close as possible to 10 -11 m/ Hz Assess reliability and longevity of key components (thrusters, capacitive sensors, optics, lasers) LTP DRS

53. LISA 52 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 LISA PF Spacecraft

54. LISA 53 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 LPF orbit

55. LISA 54 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 LISA layout

56. LISA 55 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Spacecraft Layout

57. LISA 56 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Spacecraft Layout

58. LISA 57 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Spacecraft Layout

59. LISA 58 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Payload layout

60. LISA 59 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Optical layout

61. LISA 60 Réunion 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

62. LISA 61 Réunion 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

63. LISA 62 Réunion LISA-France, Collège de France, 20/21 Janvier 2005 Instrumental Noise Armlength penalty: 5 Million kilometer Acceleration noise: 10 -15 m/(s 2 Hz) Quality of drag-free control, gravity gradient noise Shot noise: 70 pW 10 -5 cycles/ Hz

64. LISA 63 Réunion 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 (N 2 O 4 / hydrazine) system and a Reaction Control System for attitude control 13 month cruise phase

65. LISA 64 Réunion 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 ESAs SPC in June 04 (160 M) – Europe: LISA Technology Package (LTP) – US: Disturbance Reduction System (DRS)

66. LISA 65 Réunion LISA-France, Collège de France, 20/21 Janvier 2005