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LISA Interferometry TeV II Meeting Madison, Wi August 30 th , 2006

LISA Interferometry TeV II Meeting Madison, Wi August 30 th , 2006. Guido Mueller University of Florida. mueller@phys.ufl.edu. LISA. 1. Super-massive Black Hole mergers. Gravitational Wave Sources. Chandra: NGC6240. 2. Extreme mass ratio Inpirals (EMRIs).

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LISA Interferometry TeV II Meeting Madison, Wi August 30 th , 2006

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  1. LISA InterferometryTeV II MeetingMadison, WiAugust 30th, 2006 Guido Mueller University of Florida mueller@phys.ufl.edu

  2. LISA 1. Super-massive Black Hole mergers Gravitational Wave Sources Chandra: NGC6240 2. Extreme mass ratio Inpirals (EMRIs) 3. Galactic Binaries 4. … Credit: Tod Strohmayer (GSFC)

  3. LISA vs. LIGO LISA: Joint NASA/ESA project LIGO: NSF project Advanced LIGO EMRIs

  4. LISA Concept LISA Concept: • 3 Spacecraft in triangular formation • 5 Gm distance betw. S/C • Heliocentric Orbit • Measure changes in distance with 10pm/rtHz accuracy! Movie

  5. LISA Technical Challenges: • How to build a gravitational reference sensor? • Need a non-accelerated proof mass acceleration < 3x10-15 m/s-2 / rHz • How to do pm-Interferometry over 5Gm? • Interferometry Measurement System (IMS)

  6. LISA Interferometry • Goal: • Measure distances with • 10 pm/rtHz accuracy • Basics: • Laser: • Wavelength: 1mm • Power: 1 W • Telescopes: • f/1 - Cassegrain • Diameter: 40cm •  Received power: ~100pW

  7. The Main Problem The Orbit Problem: Arm lengths change by about 50.000km during 12mts orbit or by ~ 1m/s.

  8. The Orbit Problem • Arm lengths change • by about 50.000km • during 12mts orbit • or by ~ m/s. • Doppler shifts (~ MHz)

  9. The Orbit Problem • Arm lengths change • by about 50.000km • during 12mts orbit • or by ~ 1m/s. • Doppler shifts (~ MHz) • Unequal arm lengths • (frequency noise)

  10. The Orbit Problem • Arm lengths change • by about 50.000km • during 12mts orbit • or ~1m/s. • Doppler shifts (~ MHz) • Unequal arm lengths • (frequency noise) • Telescope repointing (pointing noise) Very dynamic interferometer!

  11. LISA Concept High Gain Antennas uN-Thrusters

  12. LISA Concept Optical Benches Proof Mass Housing Telescopes

  13. Interferometry • Main Components/Tasks: • Phasemeter • Laser Frequency Noise • Mechanical Noise (Solution: Engineering)

  14. Phasemeter • Requirements: • 2-20 MHz signal frequencies, changing by several MHz • Frequency noise of 30Hz/Hz1/2 @ 1mHz • = 30000 cycl./Hz1/2 @ 1mHz • need to be resolved with 10-5 cycles/Hz1/2 accuracy! •  Dynamic Range of 9 orders of magnitude.

  15. Input I Q NCO Feedback The JPL Phasemeter Tracks the Phase of RF signal with NCO I/Q demodulation with tracking NCO

  16. x107 zoom dynamic range ~109 @ 5 mHz Requirement The JPL Phasemeter Equivalent Optical Setup • Digitally tested dynamic range requirement. • Digitally generated 3 independent, laser-like noise sources such that, Phase 0+Phase 1- Phase 2 = 0 (Results from Daniel Shaddock, Brent Ware, Bob Spero, JPL)

  17. Laser Frequency Noise • Requirements: • Frequency noise of 30Hz/Hz1/2 @ 1mHz (for Phase meter) • Free running laser: ~ 1MHz/Hz1/2 @ 1mHz • Everything below 30Hz/Hz1/2 reduces requirements • on Phase meter • Solution: • Frequency stabilization • Time Delay Interferometry

  18. Frequency Stabilization Ground testing: • Two lasers independently stabilized to two reference cavities: • References: 2 Zerodur spacers with optically contacted mirrors in ultra-stable vacuum chamber • Pound Drever Hall stabilization scheme (Modulation/Demodulation) • 1st Step: Stabilize to ultra-stable reference cavity: • Baseline: ULE or Zerodur spacer ring cavity

  19. Rachel Cruz Frequency Stabilization UF-results • Similar Results • with ULE spacers: • AEI Hanover • GSFC • Can we do better?

  20. Arm Locking Basic Idea: Lock laser frequency to LISA arm Far S/C: Transponder (phase locked laser) ! S(t) = f(t-2t)-f(t) = 0 • Transfer function is zero at Fourier frequencies fN = N/2t • Requires tailored feedback gain (~1/sqrt(f)) at and above f1 up to UGF  High bandwidth, only limited gain • Laser frequency noise suppressed at all frequencies except at fN = N/2t

  21. Arm Locking Different potential realizations: Single Common Sagnac Round-trip arm length Difference between arms Sagnac effect (rotation)

  22. Arm Locking Sagnac • Sagnac: • Allows high-gain, • low-bandwidth feedback loop • Very simple design • Main disadvantage: • No redundancy: • If one link malfunctions, • the Sagnac signal is gone •  Common arm locking is the baseline Sagnac effect (rotation)

  23. Stabilized “Reference” Stabilized “Master” Phase-locked “Slave” Interferometer & arm-locking Arm Locking

  24. Arm Locking • Compare to LISA:

  25. Arm Locking • Latest Arm Locking experiment at UF • currently limited by missing real time phasemeter • EPD using 25 MHz digitization rate, delay of 1.065ms or f1 = 939Hz

  26. Arm Locking • Latest Arm Locking experiment at UF • currently limited by missing real time phasemeter • Out-of-loop • Primary beat note demodulated to 10kHz • Phase of 10kHz signal measured using software phase meter.

  27. Arm Locking • Out-of-loop • Primary beat note demodulated to 10kHz • Phase of 10kHz signal measured using software phase meter. Ira Thorpe

  28. Time Delay Interferometry • Laser frequency stabilization • Time Delay Interferometry (TDI) First Generation X-combination: Sb(t) -Sg(t) -Sb(t-2τg) +Sg(t-2τb) • Requires to know the light travel times betw. S/C • Ranging with 30m accuracy Synthetic equal arm Interferometer!

  29. TDI Experiment (Nearly) full scale LISA signal Limited by Transponder Noise

  30. TDI Experiment • Results currently limited by PLL performance 5 orders suppression Phase Noise [cycles/rt(Hz)] Rachel Cruz Frequency [Hz]

  31. Summary LISA Interferometry: Requirements: • 10pm/rtHz in a dynamic 5Gm interferometer Key Technologies: • Phase meter • Laser frequency stabilization • Reference Cavity • Arm locking • Time Delay Interferometry

  32. Summary ESA/EU: • ESA/Estec • Astrium, Germany • AEI Hanover • University Trento • University of Birmingham • University of Glasgow • … NASA/US: • GSFC • JPL • University of Florida • JILA • Stanford • University of Washington • … The End Lets get dinner! + many data analysis and theory groups

  33. Summary LISA: • Remaining Challenges: • How to move the telescope w/o distorting the measurements? • Do we need to measure these distortions and correct for them? • How to align the spacecraft to acquire lock? • Stable materials and components: • Laser switch, Fiber launcher, Vacuum system, Discharging, PAA actuator, … • Data Analysis challenges • Galactic binaries create a GW “noise” floor Does this sound different from other missions?

  34. Summary LISA: • GRS: • Will be flight tested in LTP around 2009/10 • LTP ground tests look very promising so far • Interferometry: • Basic concepts of TDI, Arm-locking, clock noise removal are well understood • Experimental tests at component level are progressing very well • EPD unit enables detailed ground testing of TDI/AL (Test as you fly, fly as you test)

  35. Summary LISA: Was considered a very challenging mission • No ground testing possible • No technology heritage for any of the major technologies: • GRS • Interferometry • Data Analysis

  36. 400x Arm Locking • Out-of-loop measurement of primary beat note using frequency counter. Ira Thorpe

  37. Delayed Prompt Prompt-Delayed TDI Experiment First experimental verification of TDI! Rachel Cruz, Michael Hartman, UF

  38. UF Simulator Electronic Phase Delay • UF technique: • Laser Phase replaced by beat note phase • Beat note phase delayed electronically (EPD). • LISA photodiodes replaced by electronic mixers. LISA

  39. Electronic Phase Delay Max. Signal System Date Hardware # Chan. Max. Delay Freq. Summer 200 kHz PCI Original 30 kHz 2 80 s 2004 card Summer Current Pentek 5 MHz 4 6 s 2005 Fall Pentek w/ Future 2 0 MHz 4 35 s * 2006 PMs & NCOs *Depends on resolution & BW

  40. Short LISA History • Foundation paper in 1984 by Bender, Faller, Hall, Hils and Vincent • Concept developed through • Concept studies ‘84-’93 • ESA Pre-Phase studies ‘93-’98 (cf., PPA2 document) • NASA Team-X study ‘98 • ESA Industrial Phase A Study ‘98-’00 (cf., FTR and STS documents) • GSFC Project Office formed in ‘01, technology planning and development commenced. • Flight demonstrations (LISA Pathfinder and ST-7) initiated in ‘00-’01 • NASA Formulation Phase began Oct. ‘04 • ESA Industrial Formulation Study begun at Astrium/Friedrichshafen Jan. ‘05, finished Phase I in Oct. ‘05 • Concept has not significantly changed since PPA2 in 1998. • Current focus • Architecture definition and refinement, design trade studies • Technology development • LISA Pathfinder and ST-7 We entered Phase A late 2004! Slide stolen from Robin ‘Tuck’ Stebbins LISA Symposium Talk

  41. Mission Status • ST7 brings the least well-tested LISA instrumentation, DRS, to TRL level 9 • Preparations for 2010 launch will already greatly enhance • Experience in building flight models • Experience in tightly-coupled NASA/ESA cooperation • Results from 2010 launch will be in time to inform formulation FY07 FY08 FY09 FY10 FY11 HW delivery launch Phase C/D Phase E Phase A (survival) Phase A Phase B Slide stolen from Colleen Hartman, LISA Symposium

  42. Mission Status • Budget requirements have necessitated Beyond Einstein be sequential missions rather than parallel efforts • Funding wedge for first BE mission start in 2009 • One of 3 will go first: LISA, Con-X, JDEM • Special BE NRC panel in 2008-9 Instead of two parallel lines of sequential missions We hear you … JDEM: Additional competition! From Colleen Hartman, LISA Symposium

  43. Optical Bench Phase Meter 2 Phase Meter 1 Phase Meter 3 Fiber to/from Second Bench to/from far SC PM from Laser Bench

  44. Optical Bench Phase Meter 1 • Bench A: • PM1A: f1(t) -f2(t) + fibernoise • Bench B: • PM1B: f1(t) -f2(t) - fibernoise • PM1A + PM1B = 2 [f1(t) - f2(t)] • Independent of fiber noise • Used to phase lock local lasers • Allows to compare both Interferometer arms • [Like having a beam splitter in a Michelson Interferometer Fiber to/from Second Bench from Laser Bench Only works if OPL in fiber is independent of propagation direction!

  45. Optical Bench Polarization Sagnac Interferometer for Optical Fiber Tests at UF Fiber Pol l/4 l/2 Laser l/4 BS Pol Parallel tests in Glasgow, Hanover

  46. Optical Bench Phase Meter 2 Phase Meter 1 Phase Meter 3 Fiber to/from Second Bench to/from far SC PM from Laser Bench PM 2 – PM 1 : Distance PM - SC

  47. Optical Bench Phase Meter 2 Phase Meter 1 Phase Meter 3 Fiber to/from Second Bench to/from far SC PM from Laser Bench PM 3: Distance SC – SC How?

  48. Optical Bench • Phase Meter 3 on S/C 2 and 3: • Used to Phase lock local laser Phase Meter 3 PM 3A – PM 1A To Laser frequency actuator ]PLL to/from far SC PM from Laser Bench

  49. LISA Master S/C Slaved S/C Slaved S/C

  50. Optical Bench • Phase Meter 3 on Master S/C 1: Phase Meter 3 PM 1A – PM 3A • = f1(t)-f1(t-2t1)+GW1 • (~Unequal Arm MI) • Dominated by Laser frequency noise df : • ~1000 cycl./rtHz noise PM from Laser Bench to/from far SC

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