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Spacecraft Gravitational Wave Detectors

Spacecraft Gravitational Wave Detectors. Wei-Tou NI Center for Gravitation and Cosmology Purple Mountain Observatory Chinese Academy of Sciences Nanjing, China. OUTLINE. Introduction – Why in space? LISA and LISA Pathfinder

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Spacecraft Gravitational Wave Detectors

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  1. Spacecraft Gravitational Wave Detectors Wei-Tou NICenter for Gravitation and Cosmology Purple Mountain Observatory Chinese Academy of Sciences Nanjing, China Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  2. OUTLINE • Introduction – Why in space? • LISA and LISA Pathfinder • General Concept of ASTROD --- ASTROD I, ASTROD, ASTROD-GW, Super-ASTROD • Primordial Gravitational Waves • Two potential frequency regions to detect primordial GWs • Outlook Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  3. Drag-free requirement makes the whole spacecraft a detector • The spacecraft is the isolation system for spurious forces Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  4. 0.1mHz-1 Hz ~10Hz-kHz Why go to Space? • Complementary to ground-based observatories that are sensitive to high frequency GWs Gravitational Wave Detectors in Space: LISA, ASTROD and Later MissionsW.-T. Ni Hubble Deep Field, HST.WFPC2, NASA

  5. Gravity gradient noise on the Earth RAS / IOP Meeting 14/02/03 B. Schutz GW sources in the high frequency band Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  6. Why in space? • Minimal Spurious Perturbations • Longer Measurement Times • Experiments in space are able to explore the GW universe and to challenge our understanding of the universe and look for slight deviations that lead to grand unification theories Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  7. Low Frequency GWs from: Gravitational Wave Detectors in Space: LISA, ASTROD and Later MissionsW.-T. Ni

  8. LISA LISA consists of a fleet of 3 spacecraft 20º behind earth in solar orbit keeping a triangular configuration of nearly equal sides (5 × 106 km). Mapping the space-time outside super-massive black holes by measuring the capture of compact objects set the LISA requirement sensitivity between 10-2-10-3 Hz. To measure the properties of massive black hole binaries also requires good sensitivity down at least to 10-4 Hz. (2017) Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  9. Massive Black Hole Systems: Massive BH Mergers &Extreme Mass Ratio Mergers (EMRIs) Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  10. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  11. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  12. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  13. Catalogs of GW sources • Typical binaries: sky positions, distance, orbit orientation, orbit separation, chirp mass for the system, spin magnitude and orientation, merger time (if appropriate) • Sources with subtantial orbital evolution: masses of the individual objects • Most favorable cases: masses, spins and distances to 1 % Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  14. LISA Instrument & Sciencecraft Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  15. LISA Pathfinder • Paul McNamara for the LPF Team • LISA Pathfinder Project Scientist • GWADW • 10th - 15th May 2009 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  16. Drag-free AOC requirements • Atmospheric (terrestrial) air column exclude a resolution of better than 1 mm • This reduces demands on drag-free AOC by orders of magnitude • Nevertheless, drag-free AOC is needed for geodesic orbit integration. Thruster requirements Proof mass-S/C coupling Control loopgain Thrust noise Proof mass Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  17. LISA Pathfinder in Assembly Clean Room Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  18. LISA Orbit Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  19. Problems on the Orbit Optimization for the LISA Gravitational Wave ObservatoryG. Li et al. (IJMPD 2008) Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  20. Interlocking Developments • Satellite/Lunar Laser Ranging in 1960s • Drag-free navigation for geodesy in 1970s • Concept of Laser Interferometry in Space for GWs in 1980s • Concept of ASTROD and Interplanetary Laser-Pulse Ranging in 1990s • Pulse and CW Optical Communication in Space Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  21. The General Concept of ASTROD • The general concept of ASTROD (Astrodynamical Space Test of Relativity using Optical Devices) is to have a constellation of drag-free spacecraft navigate through the solar system and range with one another using optical devices • to map the solar-system gravitational field, • to measure related solar-system parameters, • to test relativistic gravity, • to observe solar g-mode oscillations, • and to detect gravitational waves. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  22. Gravitational Field in the Solar System • The solar-system gravitational field is determined by three factors: • the dynamic distribution of matter in the solar system; • the dynamic distribution of matter outside the solar system (galactic, cosmological, etc.) • and gravitational waves propagating through the solar system. ------------------------- • Different relativistic theories of gravity make different predictions of the solar-system gravitational field. • Hence, precise measurements of the solar-system gravitational field test these relativistic theories, in addition to enabling gravitational wave observations, determination of the matter distribution in the solar-system and determination of the observable (testable) influence of our galaxy and cosmos. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  23. Common Science ---Astrodynamic Equation + gal-cosmo term +non-grav term Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  24. ASTROD I(Cosmic Vision 2015-25) submitted to ESA by H. Dittus (Bremen)arXiv:0802.0582 v1 [astro-ph] • Scaled-down version of ASTROD • 1 S/C in an heliocentric orbit • Drag-free AOC and pulse ranging • Launch via low earth transfer orbit to solar orbit with orbit period 300 days • First encounter with Venus at 118 days after launch; orbit period changed to 225 days (Venus orbit period) • Second encounter with Venus at 336 days after launch; orbit period changed to 165 days • Opposition to the Sun: shortly after 370 days, 718 days, and 1066 days Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  25. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  26. Laser ranging / Timing: 3 ps (0.9 mm) • Pulse ranging (similar to SLR / LLR) • Timing: on-board event timer (± 3 ps)reference: on-board cesium clock • For a ranging uncertainty of 1 mm in a distance of 3 × 1011 m (2 AU), the laser/clock frequency needs to be known to one part in 1014 @ 1000 s • Laser pulse timing system: T2L2 (Time Transfer by Laser Link) on Jason 2 • Single photon detector Jason 2 S/C Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  27. Two GOCE sensor heads (flight models) of the ultra-sensitive accelerometers (ONERA’s courtesy) 2 × 10^-12 m s^-2 Hz^-1/2 resolution in presence of more than 10^-6 m s^-2 acceleration Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  28. Summary of the scientific objectives in testing relativistic gravity of the ASTROD I and ASTROD missions Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  29. ASTROD configuration (baseline ASTROD after 700 days from launch) Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  30. A comparison of the target acceleration noise curves of ASTROD I, LISA, the LTP and ASTROD Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  31. Outgoing Laser beam Telescope Optical readout beam Dummy telescope Proof mass Large gap Anchoring Dummy telescope Proof mass Capacitive readout Housing LASER Metrology Telescope Incoming Laser beam Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  32. Solar oscillation modes • Probing the sun’s core as well as its internal structure and dynamics (with ASTROD only) • Solar gravity (g)-modes have very small amplitudes and generate very small radial velocities. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  33. Comparison of surface radial velocity amplitudes for l=2 g modes (quadrupole modes) (explanation in the text below) Theoretical estimates from [16] (thick dashed line) and [15] (thick solid line); one sigma limit corresponding to an average of 50 modes observed by the GOLF instrument with 10 years of data, derived from [10] (thin straight line); LISA one sigma limit (grey solid line) assuming a one-year integration time and a strain sensitivity of 10-23 at 3000 μHz and a f-1.75 dependence [14]; ASTROD one sigma limit (thin solid line) assuming a one year integration time and a strain sensitivity of 10-23 at 100 μHz and a f-2 dependence, with a spacecraft orbiting at 0.4 AU [14]. The surface velocity amplitudes for ASTROD were derived using the most recent GW strain sensitivities in [14] and the equations in [17]. The GW strain falls off as 1/R4, R distance to the Sun. The significant improvement provided by ASTROD with respect to LISA is due to a combination of better strain sensitivity and a smaller distance to the Sun. GOLF Observation Gough (theory) Kumar, et al. (theory) Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  34. Test of relativistic gravity and fundamental laws of spacetime • Measuring solar and planetary parameters • and Gravitational Waves Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  35. ASTROD configuration (baseline ASTROD after 700 days from launch) Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  36. ASTROD’s GW gaols-- dedicated to GW detection • Larger Armlength  More Sensitivity to Lower Frequency and Larger Wavelength • Better S/N to massive BH events  Better accuracy for cosmic distance measurement and probe deeper into larger redshift and earlier Universe. Better probe to dark energy. • More sensitive to primordial gravitational waves if foreground GWs can be separated. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  37. Time delay interferometry: Technology common to LISA and ASTROD • Although the velocity in the Doppler shift direction differ by 200-300 times, LISA and ASTROD both need to use time delay interferometry • The issue of large differences in frequency for ASTROD is ideally solved by using optical comb generator and optical frequency synthesizer together with optical clock • Data analysis for ASTROD poses big challenges Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  38. Interferometry Measurement System (IMS): Main Constituents • 40 cm, f/1.5 transmit/receive telescope • Optical bench with interferometry optics, laser stabilization • Gravitational reference sensor • 1.064 μm Nd:YAG non-planar ring oscillator master laser, 2 W Yb:YAG fiber amplifier, plus spare • Fringe tracking and phasemeter electronics, including ultra-stable oscillator • Fiber link for comparing laser phase between two arms Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  39. S/C 1 (L4) 60 地球 (L3) S/C 2 L1 L2 60 S/C 3 (L5) ASTROD-GW Mission Orbit • Considering the requirement for optimizing GW detection while keeping the armlength, mission orbit design uses nearly equal arms. • 3 S/C are near Sun-Earth Lagrange points L3、L4、L5，forming a nearly equilateral trianglewith armlength260 million km（1.732AU）. • 3 S/C ranging interferometrically to each other. Earth Sun Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  40. S/C 1 (L4) 60 地球 (L3) S/C 2 L1 L2 60 S/C 3 (L5) ASTROD-GW Mission Orbit • Considering the requirement for optimizing GW detection while keeping the armlength, mission orbit design uses nearly equal arms. • 3 S/C are near Sun-Earth Lagrange points L3、L4、L5，forming a nearly equilateral trianglewith armlength260 million km（1.732AU）. • 3 S/C ranging interferometrically to each other. Earth Sun Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  41. Difference of Armlengths in 10 years Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  42. Angle between Arms in 10 Years Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  43. Velocity in the Line-of-Sight Direction (Men, Ni & Wang) Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  44. Time delay interferometry: Technology common to LISA and ASTROD-GW • Although the velocity in the Doppler shift direction for ASTROD-GW is smaller than LISA, LISA and ASTROD-GW both need to use time delay interferometry. • For ASTROD-GW, the Doppler tracking technology developed in LISA could be used. • Telescope pointing of LISA could also be used. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  45. Motivation: Primordial Gravitational Waves are probes to very early universe --- after 10^(-43) s or even earlier • Primordial Gravitational Waves Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  46. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  47. The Gravitational Wave Background from Cosmological Compact BinariesAlison J. Farmer and E. S. Phinney (Mon. Not. RAS [2003]) Optimistic (upper dotted), fiducial (Model A, lower solid line) and pessimistic (lower dotted) extragalactic backgrounds plotted against the LISA (dashed) single-arm Michelson combination sensitivity curve. The‘unresolved’ Galactic close WD–WD spectrum from Nelemans et al. (2001c) is plotted (with signals from binaries resolved by LISA removed), as well as an extrapolated total, in which resolved binaries are restored, as well as an approximation to the Galactic MS–MS signal at low frequencies. Super-ASTROD Region DECIGO BBO Region Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  48. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  49. BIG BANG OBSERVATORY BBO;http://universe.gsfc.nasa.gov/be/roadmap.htm • The Big Bang Observatory is a follow-on mission to LISA, a vision mission of NASA’s “Beyond Einstein” theme. • BBO will probe the frequency region of 0.01–10 Hz, a region between the measurement bands of the presently funded ground- and space-based detectors. Its primary goal is the study of primordial gravitational waves from the era of the big bang, at a frequency range not limited by the confusion noise from compact binaries discussed above. • In order to separate the inflation waves from the merging binaries, BBO will identify and subtract the signal in its detection band from every merging neutron star and black hole binary in the universe. It will also extend LISA’s scientific program of measuring wavesfrom the merging of intermediate-mass black holes at any redshift, and will refine the mapping of space-time around supermassive black holes with inspiraling compact objects. • The strain sensitivity of BBO at 0.1 Hz is planned to be ∼10−24, with a corresponding acceleration noise requirement of < 10−16 m/(s2 Hz1/2). These levels will require a considerable investment in new technology, including kilowatt-power level stabilized lasers, picoradian pointing capability, multi-meter-sized mirrors with subangstrom polishing uniformity, and significant advances in thruster, discharging, and surface potential technology. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

  50. 航天器S/C2 30 太阳 60 航天器S/C *1 60 30 航天器S/C *2 航天器S/C3 地球 6 S/C ASTRODGW mission orbit 6 S/C ASTROD optimized for correlation detection • This configuration is optimized for the correlation detection of GW background 航天器S/C *3 航天器S/C1 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai

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