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# LISA Pathfinder: the complexity of free fall - Michele Armano

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Let’s face complexity September 4-8, 2017

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### LISA Pathfinder: the complexity of free fall - Michele Armano

1. 1. lisa pathfinder Michele Armano - LISA Pathfinder Scientist for the LISA Pathfinder collaboration 2017.09.06 Lake Como School of Advanced Studies “Let’s Face Complexity” LISA Pathfinder: the complexity of free fall
2. 2. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder2 Appetiser: astronomy and cosmology of the EM field
3. 3. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder3 Astronomy and cosmology of curvature and gravity •Final form of field equations of General Relativity (GR) •November 25, 1915 Academy of Science of Prussia •Article published on December 2, 1915 geometry of space-time contents of mass, energy and stress ~ causes the form determines the motion Rµ⌫ 1 2 Rgµ⌫ + ⇤gµ⌫ = 8⇡G c4 Tµ⌫
4. 4. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder4 Strain to equivalent acceleration spectrum 1 hour 1 minute 1 second Sets the minimum detectable signal for a given frequency How long does the phenomenon last? Graph per “second of observation” - valid for any physical quantity Sensitivity curve Visible (signal > noise) Invisible (noise > signal)
5. 5. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder5 What are we discussing today? •Gravity, GR and gravitational waves •production of waves •the problem of noise •Observatories •ground-based: LIGO •space-based: LISA • Science and technology of free fall and noise reduction: LISA Pathfinder • From first principles to observables • Experiments • Ground segment and operations • Results
6. 6. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder6 Gravitational Waves? •GR (perturbations of Riemann tensor): tidal waves travelling at the speed of light •Matter displacement or equivalent energy and momentum change causes variation of space- time curvature •quadrupole+ waves (momentum conservation nulls dipole) •only 2 polarisations in pure tensor theories !2 = G m1 + m2 l3 h(r, t) ' A(r) cos 2! ⇣r c t ⌘ A(r) = 4Gµ!2 l2 c4r = 8G2 m1m2 c4rl / 1 r Binary systems are prototypes: plane waves far from source
7. 7. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder7 Placing beads or gains of sand in space, at a GW passing…
8. 8. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder8 How to detect/observe/measure them? • Ring of particles • waves give particles “tidal” accelerations: simultaneous stretching and shrinking of orthogonal axes of polarisation • precision measurement of time of vibration • Maximise rest distance L to maximise signal } Δx(t) } Δy(t) h = L L ⇠ R0j0k !2 x(t) y(t) L ⇠
9. 9. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder9 Why free fall? •Does it cancel static gravity? •Yes •Why? •All bodies fall likewise towards one another (and to Earth) principle of equivalence •Tidal effect is visible
10. 10. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder10 Tides •When in free-fall tide is the only detectable effect •Who is moving versus whom? •Earth tides are the detectable effect of Moon on Earth in the field of the Sun
11. 11. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder11 That’s where interferometers come handy! LIGO (Hanford,WA) 4km 4km 1. suspended mirrors (free fall) 2. laser comes and goes in arms, packets of photons forming a ruler in space with proper time 3. difference in flight time ideally only due to dynamic gravitational perturbation 4. distance variation is incredibly small, hence L made as big as possible h ⇠ L L
12. 12. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder12 Moreover: observe GW from fluctuation of test masses Dynamic warping of space-time Animation courtesy of S.Vitale
13. 13. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder13 Lots of forces conjure to the same effect! e.g. impact with gas molecules Animation courtesy of S.Vitale
14. 14. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder14 It’s also said that we all fall the same way… more or less!
15. 15. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder15 GWs can be classified w/r to their origin (strain plot) Pulsar Timing SKA LIGOeLISA Planck Bicep2 cuerdas cósmicas y otros bichos raros Radio mm FIR IRVIS VUV X-ray γ-ray Audio band  1Hz-10kHz Ground-based ~ optical astronomy Space observation ~ radio astronomy
16. 16. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder16 Hitting a GW: pattern matching • Model of the physical system • BH/NS/…: orbital parameters, mass… • CMB/…: statistical mechanics of particles species • Solution of the problem in GR • energy, impulse, geometry and propagation • deduction of waveforms far from the source • Waveform • zoology of sources • pattern matching Example of “chirp” at collapse of BH/NS
17. 17. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder17 This “chirp” is not that unusual… Architectural chirping: windows in perspective Chirping of birds songs: luscinia luscinia/thrush nightingale luscinia megarhynchos/common nightingale
18. 18. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder18 More complicated waveforms: simulation of orbit and waves http://adsabs.harvard.edu/abs/2007CQGra..24R.113A
19. 19. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder19 From theory to Nature • Collapse of 2 BH of 29 and 36 M☉ at ~1.3 billions of light-years from Earth • gravity propagates per waves carrying information from the source • During the 0.5 s of the impact: released 50+ more energy of the light equivalent of visible stars • Final BH mass = 62 M☉, ΔW in GWs = 2 M☉ Observatory LIGO Hanford Observatory LIGO Livingston Delay ~7ms 14th September 2015 10:50:45 CET: the LIGO experiments in USA reveal GWs for the ﬁrst time in the history of Homo Sapiens MA turning 40 13th September 2015: Thanks LIGO, what a present!
20. 20. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder20 The signal Time Relativeamplitudeh=ΔL/L
21. 21. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder21 Conversion to sound
22. 22. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder22 More news from LIGO Estimate of mass and distance of BH Estimate limit mass of gravitons!
23. 23. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder23 The observatory in space: LISA •Mirrors/test-masses (TM) in assisted free fall on spacecrafts separated by millions of km (signal ~ L) •Removal of zero-point static g of Earth •Removal of unwanted phenomena •Measurement of proper distance (flight time of photons) in the arms (as in LIGO) captures the tidal perturbation of GWs •Combination (TDI) of 3x2 connexions: •TM to SC •SC to SC •SC toTM SC to TM SC to TM TM to TM Sun 1AU Sol 1 AU
24. 24. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder24 From the Mission Concept Document to the selection by the SPC • Submitted on January 13th, 2017 • The LISA Consortium: 12 EU Member States plus the US! • Selected by the Science Programme Committee for an “L3” launch in 2030+ • LISA will be reality! https://www.lisamission.org/proposal/LISA.pdf
25. 25. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder25 LISA: Sources,Astrophysics, Cosmology and Fundamental Physics • Massive BH - 1E4-1E8 M☉ - Formation? Evolution? Role in structure formation? Luminosity, redshift, mass of Graviton? • Extreme Mass Ratio Inspirals, (EMRIs) - 1-10 M☉ into 1E4-5E6 M☉ - Stellar dynamics in galactic nuclei? Kerr Metric OK? Exotic objects? GR OK? • Ultra-Compact Binaries in the Milky Way - Explosion mechanism of type-Ia supernovae. Formation, merger rates of compact binaries • Stochastic Signals - What before decoupling of CMB? Phase transitions? Higgs? Supersymmetry? Warped extra- dims? Branes?Topological defects?
26. 26. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder26 Can it be done? Trustworthy science? Where? Dynamics Orthogonality Control and feed-back Instrument displacement Instrument forces How? ? ? ? ? ? Fakes GW? ? ? ? ? ? Blinds GW? ? ? ? ? ?
27. 27. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder27 Can it be done? LISA Pathfinder (LPF) •A high precision geodesy device and gradiometer •free-fall (δa / ⍵c ≪ h) via high-precision rockets & drag-free •shielded + low- noise sensing (δF / m⍵c, ⍵ δx ≪ h) •NOT a detector for GWs (L is too small) •1arm of LISA to 38 cm!
28. 28. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder28 LISA Pathfinder
29. 29. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder29 The Optical Metrology System on LISA Pathfinder Goal is to measure changes at picometre level 1,000,000,000,000th of a metre Assess relative acceleration of test masses by measuring their relative motion
30. 30. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder Actuators Sensors 30 Sensors, injectors and controllers Charge handling IS IS TM2TM1 Drag-Free & Micro- Propulsion Attitude Control Systems Measurement processing Controllers OB StarTrackers Thrusters Thermo-meters Particle detectors Displacement/rotation inputs + Thrusters direct input + Capacitors direct input + Force/ torque inputs + Heaters + Magneto-coils + UV-lamps +
31. 31. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder C(o + oi) + gi + gn = Dq o = Sq + on 31 Towards the EOM ISs & IFO D-1- C Thrusters oi+ gi + S qo on gn TMs reaction SC reaction Dynamics ⟂ Control and feed-backD S C ongn Noise oi gi Inputs
32. 32. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder = gn + DS-1 onCoi gi + (DS-1 + C)o 32 Models and residuals acceleration noiseF, Δx inputs D SC ongn g S Fit of coefﬁcients in noise Where? Dynamics Orthogonality Control and feed-back Instrument displacement Instrument forces How? Non-null couplings (1st order ~Hooke) Reference errors Control errors Interferometers Capacitors, thrusters Fakes GW? Glitches Jitter Blinds GW? Electrostatics, thermal, magnetics, self- gravity Mixing, cross-talk Motion suppression, electrostatics Noisy readout Noisy forces Enhancement by injection
33. 33. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder33 Experiments scenario Acceleration measurement System identification & Cross-talk Laser Optics Free-fall and unassisted drift Magnetic perturbations Thermal perturbations Radiation and particles monitoring Dynamics Physics zoo (HW and Environment couplings) Charging Parasitic voltages and DC patches
34. 34. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder34 Calibration of Interferometry IS2IS1 OB TM2TM1 o1o12
35. 35. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder35 Title Text 08:00-12:00 12:00-16:00 16:00-20:00 20:00-24:00 24:00-04:00 04:00-08:00 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 IS RO calibcapacitors IFO RO calib acc meas 8h acc meas 8h 2h acc meas 8h acc meas 8h acc meas 8h acc meas 8h acc meas 4h acc meas 8h acc meas 4h acc meas 8h acc meas 6h 1 acc meas 8hacc meas 8h acc meas 4h acc meas 8h acc meas 4h acc meas 6h 2hacc meas 4h acc meas 4h acc meas 6h 1 acc meas 4h
36. 36. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder36 System Identification Coi gi + (DS-1 + C)o = g x1 += sin(…) >> F_X >> IFO(x2 - x1) 1. 2. x2 += sin(…) >> F_x2 >> IFO(x2 - x1) >> IFO(x1) 3. Three-body: [x1, x2, X] += sin(…), read [F_X, F_x1, F_x2] & ﬁt with same outputs.Activation of x1 actuation electrodes required. # t0 duration A f 1 500 1000 6.99E-09 0.001 2 2000 1000 2.20E-09 0.003 3 3500 715 8.85E-10 0.007 4 4715 462 9.56E-10 0.013 5 5677 412 1.20E-09 0.017 6 6589 474 1.33E-09 0.019 7 7563 479 1.59E-09 0.023 8 8542 483 2.03E-09 0.029 9 9525 566 4.53E-09 0.053 >> IFO(x1) # t0 duratio n A f 1 500 1000 1.00E-08 0.001 2 2000 1000 1.00E-08 0.003 3 3500 715 9.72E-09 0.007 4 4715 462 6.00E-09 0.013 5 5677 412 4.56E-09 0.017 6 6589 474 4.05E-09 0.019 7 7563 479 3.32E-09 0.023 8 8542 483 2.40E-09 0.029 9 9525 566 7.09E-10 0.053
37. 37. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder37 Fits? Examples from simulated datasets… ¨o12 = c1 ¨1 + c2 1 c3N 1 !2 2(o12 + o1) + !2 1o1 Asusfcmd,x2 ¨o12 ! ¨o12 c4 ¨2 1LTPDA 2.8.dev (R2012b) 2014−01−19 17:46:44.815 UTC ltpda: cbf5bb4 iplot 10 −5 10 −4 10 −3 10 −2 10 −1 10 0 10 −16 10 −15 10 −14 10 −13 10 −12 10 −11 10 −10 [ms−2 Hz−1/2 ] Frequency [Hz] sqrt(PSD(split(o12 acc))) sqrt(PSD(split(diff(LAT10005)))) sqrt(PSD(residuals)) ¨o12 ! ¨o12 + c5( ¨y1 ¨y2)
38. 38. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder38 Title Text 08:00-12:00 12:00-16:00 16:00-20:00 20:00-24:00 24:00-04:00 04:00-08:00 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 acc meas 8h acc meas 8h 2h acc meas 8h acc meas 8h acc meas 8h acc meas 8h acc meas 4h acc meas 8h acc meas 4h acc meas 8h acc meas 6h 1 acc meas 8hacc meas 8h acc meas 4h acc meas 8h acc meas 4h IS RO calibcapacitors calib displ 4h calib displ 4h 3-bodies 4h 3-bodies 4hact loops 4h act loops 4h phi1-o1-o12 phi2-o1-o12 eta1-o1-o12 eta2-o1-o12 Phi-o1-o12 4h theta1-o1-o12 theta2-o1-o12 Phi-o1-o12 4h phi1-o1-o12 phi2-o1-o12 Stiffness match Stiff unmatch IFO RO calib acc meas 6h 2hacc meas 4h acc meas 4h acc meas 6h 1 acc meas 4h Residual acceleration down to ~1E-14 m/s^2/sqrt(Hz)
39. 39. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder39 Know thy (DC) potential! • Patches of charge populate theTMs surfaces • Gradients of electric field are created: noise and fluctuation into the readout and more “springs”! • These potentials can be suppressed by per-electrode voltage compensation • TheTMs potential and total charge can be measured and varied via UV- lamps beamingVTM V1 V2 V3 V... Vact V1 V2 V... Vact V equiv
40. 40. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder40 Thermal experiments IS2IS1 OB TM1 TM2 Heater 1 1 Thermometers Heater 3 Heater 2 Heater 4 2 3 4 7 8 5 6 Optical Windows heaters and thermometers
41. 41. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder41 Thermals •Contribution to acceleration noise: •Measure and fit: gn ! gn + GIS · TIS = gn +  ↵IS1 0 ↵IS1 ↵IS2  T1 T2 0 2000 4000 6000 8000 10000 293 time [s] 0 2000 4000 6000 8000 10000 −0.2 −0.1 0 0.1 0.2 time [s] ΔT[K] Figure 7.12: Scheme of the absolute temperature of the EH walls and the di erential tem the EH walls. The signals in this plot are very simpliﬁed, however, they g about the temperature evolution during the test. 0 2000 4000 6000 8000 10000 −80 −60 −40 −20 0 20 40 60 80 displacement[nm] time [s] o 1 o 12 Figure 7.13: Displacement of the test masses when perturbing TM 2 with the tempera shown in Figure 7.12. 0 2000 4000 6000 8000 10000 293 293.5 time [s] T[K] 0 2000 4000 6000 8000 10000 −0.2 −0.1 0 0.1 0.2 time [s] ΔT[K] Figure 7.12: Scheme of the absolute temperature of the EH walls and the di erential tem the EH walls. The signals in this plot are very simpliﬁed, however, they g about the temperature evolution during the test. 0 2000 4000 6000 8000 10000 −80 −60 −40 −20 0 20 40 60 80 displacement[nm] time [s] o 1 o 12 ↵IS(T, p) = ATM mTM ✓ 16 3 c T3 + 1 2 p T + outgas T2 ◆ ' T3 + T {a , T, T} : a (t) = T3 (t) T(t) + T(t) T(t)
42. 42. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder42 Magnetic experiments IS2IS1 OB TM1 TM2 Coil 1 Coil 2
43. 43. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder43 Magnetics •Linear acceleration (x) •Angular acceleration (y, z) DDS-LTP Ref. S2-IEC-TN-3 Version Magnetic experiments on board the LTP Date 16/Jan/2 Page 15 0 500 1000 1500 2000 2500 3000 3500 4000 −10 −8 −6 −4 −2 0 2 4 6 8 10 time [s] displacement[nm] o1 o12 Figure 6.1: Relative distance variations between TM1 and TM2 (blue line) and variations o distance between TM1 and the EH (red line) when a current of 1 mA at a frequ of 1 Hz is fed to the coil next to TM1. The red line shows that the S/C mot considerably noisier than that of the TMs. If the TM magnetisation happens to be homogeneous throughout its volume then we the simpliﬁed expression 1 o1 and o12 for 1 mA current at 1 Hz into Coil 1 N = D M ^ B0 + r ^ (M · r) B0+ µ0 r ^ (Benv · r) B0 E V sin !0t Fx = ⌧✓ M + µ0 Benv ◆ · rB0x V sin !0t + hB0 · rB0xi 2µ0 V hB0 · rB0xi 2µ0 V cos 2!0t 1⍵ DC 2⍵
44. 44. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder 08:00-12:00 12:00-16:00 16:00-20:00 20:00-24:00 24:00-04:00 04:00-08:00 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 44 TitleText acc meas 6h acc meas 8h magnetics 7h magnetics 7h ... thermals 21h acc meas 8h 2h thermals 21h ... acc meas 6h 2h acc meas 8h 1 2h 1 Stiffness match acc meas 8h acc meas 8h acc meas 8h IS RO calib acc meas 4h acc meas 8h acc meas 4h capacitors acc meas 8h laser laser laser OPD acc meas 6h 1 acc meas 8hacc meas 8h acc meas 4h acc meas 8h acc meas 4h calib displ 4h calib displ 4h 3-bodies 4h 3-bodies 4hact loops 4h act loops 4h phi1-o1-o12 phi2-o1-o12 eta1-o1-o12 eta2-o1-o12 Phi-o1-o12 4h theta1-o1-o12 theta2-o1-o12 Phi-o1-o12 4h phi1-o1-o12 phi2-o1-o12 acc meas 4h Stiff unmatch acc meas 4h IFO RO calib acc meas 4h Q1 Q2 Q1 Q2 Q1 DC-el Q estimate + UV 17hQ1 DC-el phi1 6h DC-el x1 6h DC-el phi1 6h DC-el x2 6h DC-el x1 6h DC-el phi1 6h DC-el x2 6h Q2 Q1 Q2 Q2
45. 45. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder45 Planning, Downlink, Uplink Science Technology Operations Center POR 2016 02 20 ICE TM & DA Mission timeline (set of Payload Operations Requests) POR 2016 02 21 POR 2016 02 22 POR 2016 02 23 POR 2016 02 24 POR 2016 02 25 ... Full/HK TM & DA DataAnalysisandReplan AOS LOS MOC Remote analysis centers •Telemetry validation •Analysis with qualiﬁed pipelines •Is the scientiﬁc objective met? •Simulations? re-planning? •Send inputs to Mission Operations Control/SC
46. 46. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder46 2015.11.12 Kourou 2015.11.20 Kourou
47. 47. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder47 2015.12.03 04:04 UTC
48. 48. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder48 LISA Pathfinder mission timeline Date Milestone 3 Dec 2015 Launch, apogee-raising maneuvers, insertion into L1 orbit 11 Jan 2016 Activation of the LISA Technology Package 2 Feb 2016 Unlocking of the TMs and venting to space 15 & 16 Feb 2016 De-caging of the TMs: both TMs free-ﬂoating in controlled motion 18 Feb 2016 Alignment of the interferometer 22 Feb 2016 First entry into Science Mode: assisted free-fall 1 Mar 2016 Start of Science Operations +30 dias Acceleration measurement and calibration of the parameters of the system. Charge measurement and ﬁrst thermal experiments +30 dias Measurement of parasitic voltages on the TMs. Progressive reduction of control authority. Discharge of TMs. Characterisation of the interferometer +30 dias Early magnetic experiments. More measurements of acceleration. Measurements of charge with calibration tones. More characterisation of interferometry. More thermals and magnetics. Free-fall with drift and jumps. Final calibration 29 Jun - 1 Dec 2016 Start of operations of the Disturbance Reduction System (NASA/JPL) 1 Dec 2016-30 Jun 2017 Mission extension 6 Apr 2017 Pulling-out of cruise orbit 18 Jul 2017 Passivation of the SC. End of the LPF mission
49. 49. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder49 LPF Operations Worldwide Cebreros Antenna GSFC (Greenbelt) New Norcia Perth Malargüe Antenna JPL [DRS/ST7] (Pasadena) UTN (Trento) IEC Barcelona ICL (London) AEI (Hanover) UGL (Glasgow) Operations Centre PI Center / DA Ground Station APC (Paris) ESTEC (Noordwijk) Kourou ETH (Zurich) ESAC [STOC] (Madrid) ESOC [MOC, STOC] (Darmstadt) Rome Univ. TorVergata Urbino Univ. ESAC Madrid
50. 50. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder50 LPF for your friends and families… 3E-16 kg: e.g. Prochlorococcus cyanobacteria the smallest and most diffuse photosynthetic organism on Earth https://en.wikipedia.org/wiki/Orders_of_magnitude_(mass)
51. 51. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder51 And we’ve made it! http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.231101
52. 52. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder52 LISA and LISA Pathfinder requirements g(t) . = ¨x(t) + !2 2 x(t) + !2 12x1(t) gc(t) g⌦(t) Strain to equivalent acceleration spectrum 10-14m s-2: 1 millionth of a billionth of acceleration due to gravity on Earth (Femto-g)
53. 53. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder53 First day of operation. March 1st, 2016 g(t) . = ¨x(t) + !2 2 x(t) + !2 12x1(t) gc(t) g⌦(t)
54. 54. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder54 April 8-14, 2016 - Phys. Rev. Lett. 116, 231101 Decreased: elapsed time and basic instrument optimisation Removal of centrifugal forces induced by SC quasi-static rotation and noisy star-trackers For both curves: removal of SC motion leaking into x by angular contamination (eta, phi)
55. 55. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder55 The limiting disturbances Einstein’s thermal noise: gas molecules hitting the test-masses Scales with residual gas pressure Interferometer noise No real test-mass motion
56. 56. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder56 May 16-18, 2016. Pressure gone further down. System continuously vented to outer space
57. 57. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder57 The low frequency tail Low frequency extra noise Found to decay with time
58. 58. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder58 Explaining the noise: investigations ongoing Low-frequency noise decay being investigated: probably a mix of thermal and mechanical effects thermo-mechanical system relaxation and/or pressure gradients
59. 59. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder59 Best results: February 2017
60. 60. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder60 This result boosted LISA! Sensitivity curve of LISA from the LPF calibrated sensors/laser
61. 61. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder61 Black Hole Astronomy by 2030 aLIGO, aVIRGO, KAGRA SKA, Pulsar Timing Future EM Obs. LSST, JWST, EELT Mass [log M/M☉]à RedshiftZà ET (proposed) Graphics courtesy of K.Danzmann
62. 62. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder62 Black Hole Astronomy by 2030 SNR LISA RedshiftZà Mass [log M/M☉]à Graphics courtesy of K.Danzmann
63. 63. ESA UNCLASSIFIED - For Ofﬁcial Use - lisa pathfinder63 This is still a school in physics! Recommended reading… •Best course on GW I’ve seen: Caltech's Physics 237-2002 - Gravitational Waves (Thorne, Bondarescu, Chen) http:// elmer.tapir.caltech.edu/ph237/ •Misner,Thorne,Wheeler “Gravitation”, Freeman •Maggiore,“Gravitational Waves”, Oxford •MA Ph.D.Thesis on LPF https://arxiv.org/ abs/1110.3031 •The top-science LPF publication http:// journals.aps.org/prl/abstract/10.1103/ PhysRevLett.116.231101
64. 64. lisa pathfinder THANKS! http://sci.esa.int/lisa-pathﬁnder/