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Current Activities and Status of Lunar Laser Ranging Worldwide

ISSI LLR Workshop, Berne, February 15-19, 2010. Current Activities and Status of Lunar Laser Ranging Worldwide. Jürgen Müller Institut für Erdmessung (Institute of Geodesy) Leibniz Universität Hannover (University of Hannover) Germany. Contents. Introduction - Motivation

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Current Activities and Status of Lunar Laser Ranging Worldwide

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  1. ISSI LLR Workshop, Berne, February 15-19, 2010 Current Activities and Status of Lunar Laser Ranging Worldwide Jürgen Müller Institut für Erdmessung (Institute of Geodesy) Leibniz Universität Hannover (University of Hannover) Germany

  2. Contents Introduction - Motivation Lunar Laser Ranging - Data (distribution and accuracy) - Analysis Science Examples - relativity - lunar interior Conclusions - Future capabilities

  3. Acknowledgement Work has been supported by DFG Research Unit FOR584 Earth Rotation and Global Dynamic Processes - Liliane Biskupek - and the Centre of Excellence QUEST (Quantum Engineering and Space-Time Research) - Franz Hofmann -

  4. Retro-Reflectors and Observatories First reflector deployed on July 21, 1969 (Apollo 11) Continuous LLR observations for 40 years

  5. Statistics - Reflectors and Observatories

  6. Number of Normal Points • 1970 - 2009: ca.16,800 normal points

  7. Observations wrt. Synodic Month Moon Full Moon New Moon Sun No data No data Earth - large data gaps near Full and New Moon

  8. Observations wrt. Synodic Month (2) i Observations per 100 bin  large data gaps near Full and New Moon Synodic Angle (degree)

  9. Observations wrt. Sidereal Month Observations per 100 bin  uneven distribution as no observatory on the Southern hemisphere Sidereal Angle (degree)

  10. Status, Perspective at the LLR Sites • McDonald will (cease) lunar tracking in February 2010, but LRO tracking • APOLLO will also start LRO tracking • Grasse with first new lunar normal points (end 2009) • Matera plans to re-start LLR • Wettzell plans to use old SLR system for lunar tracking …

  11. Main Research at Lunar Analysis Centers • Jet Propulsion Laboratory (JPL) • lunar interior, lunar core • relativity • ephemeris • Paris Observatory Lunar Analysis Center (POLAC) • libration theory • reference frames • Institute of Geodesy (IfE) • Earth orientation • lunar interior • relativity • Others • special topics

  12. LLR Analysis Analysis - model based upon Einstein's Theory - least-squares adjustment - determination of the parameters of the Earth-Moon system (about 180 unknowns, without EOPs) Results of major interest - station coordinates and velocities (ITRF2000) - GGOS - Earth rotation, s = 0.5 mas (IERS) - relativity parameters (grav. constant, equivalence principle, metric ...) - ... lunar interior ... GGOS – Global Geodetic Observing System

  13. Relativistic LLR Model Model based upon Einstein's theory • transformation between reference systems (Earth, Moon, inertial) • transformation between time systems • orbital motion of the solar system bodies • rotation of Earth and Moon • gravitational time delay (Shapiro effect)

  14. Weighted Annual Residuals weightedresiduals (observed - computed Earth-Moon distance), annuallyaveraged • model? • observations? ?

  15. Science Example: Nordtvedt Effect Test ofthe strong equivalenceprinciple: • Shiftofthe lunar orbittowardsthe Sun? No! -- Realisticerror: below 1 cm

  16. Relativistic Parameters – Power Spectra Equivalence principle mG/mI anomal 412 d = anom-syn 2syn syn 31.8d = 2syn-anomal 206 d = 2anom-2syn ~10 d 132 d = 2anom-2syn+ann

  17. Relativistic Parameters from LLR • Gravito-magnetic effect in equations of motion via preferred-frame parameter • (here, coupled with dynamics within the solar system), • (Soffel et al., 2008, Phys.Rev.D, 78) • Strong Equivalence Principle, limit for Nordtvedt parameter • (Müller et al., 2008, J.Geod., 82) • Secular and quadratic variation of the gravitational constant • (Müller and Biskupek, 2007, • Class.Quant.Grav., 24)

  18. Rotation of the Moon J inertia tensor w angular velocity L external torque h relative angular momentum Euler-Liouville Equation Relativistic description ?!

  19. Lunar Interior Lunar rotation • libration angles, s = 0.001“ • numerically integrated Lunar tides - Love number k2 = 0.024 ± 0.003 Dissipation from - fluid core (Rc < 354 km) - solid mantle, Q = 38 ± 4

  20. Further Applications Reference frames • dynamic realisation of the ICRS by the lunar orbit, s < 0.01“ (stable, highly accurate orbit, no non-conservative forces from atmosphere) Earth orientation • Earth rotation (e.g. UT0, VOL) • long-term nutation coefficients, precession Relativity • test of further theories, Lense-Thirring effect Combination with other techniques

  21. New Combined Products Earth orientation • UT0 (VLBI) • Long-periodic nutation, precession (VLBI, GPS, SLR) Celestial reference frame • Dynamic realisation of ICRS, ephemeris • tie between the lunar network and the radio reference frame (VLBI) Gravitational physics parameters • Space curvature (VLBI) • Lense-Thirring precession (SLR) • Others (Grav. constant, equivalence principle metric) Lunar interior (future lunar missions)

  22. Future Lunar Missions Lunar Reconnaissance Orbiter (LRO) Deployment of transponders (6 yr lifetime) and new retro-reflectors on the Moon or in lunar orbit - more observatories - tie to VLBI (inertial reference frames) New high resolution photographs of reflector arrays - better lunar geodetic network - lunar maps

  23. New Ranging Measurements – Why? New data needed to constrain lunar interior structure • improve measurements of forced librations • measure tidal distortion (amplitude and phase) • lunar oscillations as response to large quakes or impacts? Improve on limits of relativistic effects • time variability of the gravitational constant • test of strong equivalence principle (Nordtvedt effect) Improve the tie between the lunar network and the radio reference frame (VLBI) Above goals require more data, more accurate data, and unbiased measurements!

  24. Conclusions LLR contributes to better understanding of - Reference frames (ITRF, dynamic ICRF) - Earth orientation (IERS) - Earth-Moon system - Relativity - Lunar interior - … … and supports Global Geodetic Observing System In future: new lunar ranging experiment (and combination with other techniques)

  25. Results - Relativity

  26. Results – Relativity (2)

  27. Relativistic Parameters – Power Spectra (2) Gravito-magnetic effect (PPN parameter a1) in the solar system a1=(1.6  4)·10-3 Soffel et al. 2008, PRD

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