Survey

Document related concepts

Transcript

Spacecraft Gravitational Wave Detectors Wei-Tou NI Center for Gravitation and Cosmology Purple Mountain Observatory Chinese Academy of Sciences Nanjing, China 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 1 OUTLINE 2009.10.26 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 2 2009.10.26 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 3 Why go to Space? • Complementary to ground-based observatories that are sensitive to high frequency GWs 0.1mHz-1 Hz 2006.03.18. ~10Hz-kHz Gravitational Wave Detectors in Space: LISA, ASTROD and Later Missions W.-T. Ni 4 Hubble Deep Field, HST.WFPC2, NASA GW sources in the high frequency band Gravity gradient noise on the Earth RAS / IOP Meeting 14/02/03 B. Schutz 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 5 Why in space? 2009.10.26 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 6 Low Frequency GWs from: 2006.03.18. Gravitational Wave Detectors in Space: LISA, ASTROD and Later Missions W.-T. Ni 7 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 102-10-3 Hz. To measure the properties of massive black hole binaries also requires good sensitivity down at least to 10-4 Hz. (2017) 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 8 Massive Black Hole Systems: Massive BH Mergers & Extreme Mass Ratio Mergers (EMRIs) 2009.10.26 9 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 2009.10.26 10 Space craft Gravit ational Wave Detect ors W-T Ni Galilio -Xu, Shang hai 2009.10.26 11 Space craft Gravit ational Wave Detect ors W-T Ni Galilio -Xu, Shang hai 2009.10.26 12 Space craft Gravit ational Wave Detect ors W-T Ni Galilio -Xu, Shang hai Catalogs of GW sources 2009.10.26 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 13 LISA Instrument & Sciencecraft 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 14 LISA Pathfinder 2009.10.26 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 15 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 Thrust noise 2009.10.26 Proof mass Proof massS/C coupling Spacecraft Gravitational Wave Detectors Control loop gain W-T Ni Galilio-Xu, Shanghai 16 LISA Pathfinder in Assembly Clean Room 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 17 LISA Orbit 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 18 Problems on the Orbit Optimization for the LISA Gravitational Wave Observatory G. Li et al. (IJMPD 2008) 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 19 Interlocking Developments 2009.10.26 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 20 The General Concept of ASTROD 2009.10.26 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 21 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. 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 22 Common Science --- Astrodynamic Equation r ij ri (1PN ) 2PN r（i G - wave ) (i 0,1, , n) ri 3 j i j r ij + gal-cosmo term +non-grav term ri (Post Newton ) Aij 1 r 3 ij r 2 i 1 c 2 1 r 3 A r B r j i r ij 2 ij ij j 3 2r ij ij ij rij r j 1 2 2 5 ij r 4 i j i ij 2 2 1 2 1 2 1.5 1 3 3 3 3 3 3 r ij r ik k r ij r ik k i , j r ij r jk r jk r ij r jk r ik 2r jk r ij B ij r 2 1 r r r ij 3 ij j ij r（i G - wave ) Ri x dotx dotx 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 23 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 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 24 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 25 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 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 26 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 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 27 Summary of the scientific objectives in testing relativistic gravity of the ASTROD I and ASTROD missions 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 28 ASTROD configuration (baseline ASTROD after 700 days from launch) Inner Orbit Earth Orbit 1 . Earth L1 point S/C (700 days after 1* launch) Outer Orbit -V1 L3 U2 n̂3 . U1 Launch Position 2* S/C 2 2 . Sun n̂2 -V3 n̂1 L2 L1 U3 -V2 . 3 3* S/C 1 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 29 A comparison of the target acceleration noise curves of ASTROD I, LISA, the LTP and ASTROD 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 30 Anchoring Dummy telescope Outgoing Laser beam Proof mass LASER Metrology Capacitive readout Housing Telescope Optical readout beam Telescope Incoming Laser beam Dummy telescope 2009.10.26 Proof mass Large gap Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 31 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. 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 32 GOLF Observation Gough (theory) Kumar, et al. (theory) 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. 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 33 Test of relativistic gravity and fundamental laws of spacetime Measuring solar and planetary parameters and Gravitational Waves 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 34 ASTROD configuration (baseline ASTROD after 700 days from launch) Inner Orbit Earth Orbit 1 . Earth L1 point S/C (700 days after 1* launch) Outer Orbit -V1 L3 U2 n̂3 . U1 Launch Position 2* S/C 2 2 . Sun n̂2 -V3 n̂1 L2 L1 U3 -V2 . 3 3* S/C 1 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 35 ASTROD’s GW gaols -- dedicated to GW detection 2009.10.26 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 36 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 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 37 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 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 38 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 triangle with armlength 260 million km（1.732 AU）. 3 S/C ranging interferometrically to each other. 2009.10.26 Spacecraft Gravitational Wave Detectors S/C 1 (L4) (L3) S/C 2 Sun Earth 60 球地 L1 L2 60 S/C 3 (L5) W-T Ni Galilio-Xu, Shanghai 39 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 triangle with armlength 260 million km（1.732 AU）. 3 S/C ranging interferometrically to each other. 2009.10.26 Spacecraft Gravitational Wave Detectors S/C 1 (L4) (L3) S/C 2 Sun Earth 60 球地 L1 L2 60 S/C 3 (L5) W-T Ni Galilio-Xu, Shanghai 40 Difference of Armlengths in 10 years 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 41 Angle between Arms in 10 Years 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 42 Velocity in the Line-of-Sight Direction (Men, Ni & Wang) 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 43 Time delay interferometry: Technology common to LISA and ASTROD-GW 2009.10.26 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 44 Motivation: Primordial Gravitational Waves are probes to very early universe --- after 10^(-43) s or even earlier Primordial Gravitational Waves 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 45 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 46 The Gravitational Wave Background from Cosmological Compact Binaries Alison 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) singlearm 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. 2009.10.26 Super-ASTROD Region Spacecraft Gravitational Wave Detectors W-T Ni DECIGO BBO Region Galilio-Xu, Shanghai 47 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 48 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. 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 49 6 S/C ASTROD optimized for correlation detection 航天器S/C *3 航天器S/C2 This configuration is optimized for the correlation detection of GW background 太 30 阳 60 航天器S/C *1 60 航天器S/C1 30 航天器S/C *2 航天器S/C3 地球 6 S/C ASTROD GW mission orbit 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 50 Super-ASTROD (1st TAMA Meeting1996) W.-T. Ni, “ASTROD and gravitational waves” in Gravitational Wave Detection, edited by K. Tsubono, M.-K. Fujimoto and K. Kuroda (Universal Academy Press, Tokyo, Japan, 1997), pp. 117-129. 2009.10.26 With the advance of laser technology and the development of space interferometry, one can envisage a 15 W (or more) compact laser power and 2-3 fold increase in pointing ability. With these developments, one can increase the distance from 2 AU for ASTROD to 10 AU (2×5 AU) and the spacecraft would be in orbits similar to Jupiter's. Four spacecraft would be ideal for a dedicated gravitationalwave mission (Super-ASTROD). Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 51 Primordial Gravitational Waves [strain sensitivity (ω^2) energy sensitivity] 0.0 -2.0 -4.0 -6.0 bar-intf 2 intf Nv = 3.2 (c) cosmic strings (b) String -10.0 Log [h Ωgw] 2 cosmology -12.0 -14.0 -16.0 (single intf) Nv = 4 -8.0 0 LIGO or VIRGO ms pulsars inflation ‘Average’ ASTROD -18.0 *ASTROD (correlation detection) -22.0 2009.10.26 DECIGO/BBO-grand (correlation detection) Super-ASTROD -20.0 -24.0 -18.0 LIGO II/LCGT/VIRGO II (2 adv intf) Extragalactic Extrapolated WMAP (a) LISA * Super-ASTROD (correlation detection) -14.0 -10.0 -6.0 -2.0 Log f Spacecraft Gravitational Wave Detectors [[[ [f(Hz)] 2.0 W-T Ni 6.0 10.0 Galilio-Xu, Shanghai 52 Primordial GW and Space Detectors 2009.10.26 For detection of primordial GWs in space. One may go to frequencies lower or higher than LISA bandwidth where there are potentially less foreground astrophysical sources to mask detection. DECIGO and Big Bang Observer look for gravitational waves in the higher range ASTROD-GW, Super-ASTROD look for gravitational waves in the lower range. Super-ASTROD: 3-5 spacecraft with 5 AU orbits together with an Earth-Sun L1/L2 spacecraft and ground optical stations to probe primordial gravitational-waves with frequencies 0.1 μHz - 1 mHz and to map the outer solar system. Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 53 Sensitivity to Primordial GW 2009.10.26 The minimum detectable intensity of a stochastic GW background is proportional to detector noise spectral power density Sn(f) times frequency to the third power with the same strain sensitivity, lower frequency detectors have an f ^(-3)-advantage over the higher frequency detectors. compared to LISA, ASTROD has 140,000 times (52^3) better sensitivity due to this reason, while Super-ASTROD has an additional 125 (5^3) times better sensitivity. arXiv:0905.2508 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 54 Primordial Gravitational Waves [strain sensitivity (ω^2) energy sensitivity] 0.0 -2.0 -4.0 -6.0 bar-intf 2 intf Nv = 3.2 (c) cosmic strings (b) String -10.0 Log [h Ωgw] 2 cosmology -12.0 -14.0 -16.0 (single intf) Nv = 4 -8.0 0 LIGO or VIRGO ms pulsars inflation ‘Average’ ASTROD -18.0 *ASTROD (correlation detection) -22.0 2009.10.26 DECIGO/BBO-grand (correlation detection) Super-ASTROD -20.0 -24.0 -18.0 LIGO II/LCGT/VIRGO II (2 adv intf) Extragalactic Extrapolated WMAP (a) LISA * Super-ASTROD (correlation detection) -14.0 -10.0 -6.0 -2.0 Log f Spacecraft Gravitational Wave Detectors [[[ [f(Hz)] 2.0 W-T Ni 6.0 10.0 Galilio-Xu, Shanghai 55 Summary 2009.10.26 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 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 56 Thank you ! 2009.10.26 Spacecraft Gravitational Wave Detectors W-T Ni Galilio-Xu, Shanghai 57