“The Moon as a Test Body for General Relativity and New Gravitational Theories” Marco Garattini LNF-INFN, Frascati, Italy Lunar Laser Ranging Apollo 8 Earth-rise photo Vulcano Workshop 2010 Frontier Objects in Astrophysics and Particle Physics Vulcano (Italy), 24-29 May 2010 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Outline 1. Introduction to Lunar Laser Ranging 2. Lunar Laser Ranging Physics Objectives 3. 2 nd Generation of Lunar Laser Ranging 4. The New Maryland/Frascati Payload 5. Thermal and Optical Tests in Frascati 6. Conclusions: tight US-Italy collaboration 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Laser Ranging concept: Laser Ranging concept: Laser -retroreflector retroreflector - receiving telescope - time of flight - receiving telescope - time of flight Laser - Total Internal Reflection Cube corner retro-reflectors (CCRs) Time of flight, atmospheric corrections t t t � = � stop start Retro-reflection stop c t � d � 2 Normal reflection start LASER 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
1 st st Gen. Gen. Lunar Lunar Reflector Reflector Arrays Arrays 1 Apollo 15, 1971 Apollo 11, 1969 D. Currie et al. Lunokhod 2, 1970 Apollo 14, 1971 Lunokhod 1,1970 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Lunar Laser Ranging: accurate at ~ 10 -11 of Earth-Moon distance Relative sizes and separation of the Earth–Moon. An LLR pulse takes 1.255 sec for the mean orbital distance Distance Earth-Moon ~ 384,000 km Locations of Locations of st Gen. Lunar 1 st Gen. Lunar 1 Retroreflector Retroreflector Arrays Arrays 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
LLR physics data analysis • General Relativity (GR) equations of motion – LLR provides not just one, but a suite of physics measurements, which have given a deep and thorough, weak-field, slow-motion test of GR • PPN parameters • Other new physics beyond GR (1/r 2 deviations, braneworlds …) • Description of Earth & Moon as rigid bodies • Earth & Moon geophysics (tides, librations, interiors, tectonic plate motion …) 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
LLR PHYSICS OBJECTIVES LLR data triggered (for up to factor 100 improvement over 1 st Gen. LLR) 2000 papers 10000 refs Limit with Limit with Current Measurem. PHENOMENON 1 mm 0.1 mm limit timescale LLR LLR Weak Equivalence 10 -13 ~ 10 -14 ~ 10 -15 2 yr Principle, WEP ( a/a) Strong EP, SEP 4 × 10 -4 ~ 10 -5 ~ 10 -6 (Nordtvedt param. ) 2 yr ~ 10 -5 ~ 10 -6 ~10 -4 (PPN param. ) 10 -12 /yr ~ 10 -13 /yr ~ 10 -14 /yr Gdot/G 4 yr Geodetic (de Sitter ) 6 × 10 3 ~ 5 × 10 4 ~ 5 × 10 5 6-10 yr Precession Deviations from 1/r 2 3 × 10 11 × ~ 10 12 ~ 10 13 (Yukawa param. Newtonian 6-10 yr at 10 8 m scales ( ) gravity 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
LLR SEP test: implications on PPN β Williams et al, arXiv: gr-qc/0507083v2, 2 Jan 2009 • SEP violation is due to self-energy contribution only; it can be expressed as [(M G /M I )] SEP = 1 + η (U/Mc 2 ) U = gravitational self-energy Note: U/M ∝ M = > to test SEP need astronomical bodies = > only LLR Theory prediction • [(M G /M I ) earth - [(M G /M I ) moon ] SEP = [U e /Mc 2 - U m /Mc 2 ] × η = - 4.45 × 10 -10 × η • Considering only PPN β and γ η = 4 β − γ − 3 = (4.4 ± 4.5) × 10 -4 β described the degree of non. Using Cassini’s value of linearity of gravity associated to a • SEP violation γ β − 1 = (1.2 ± 1.1) × 10 -4 Best measurement to date 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Limits on 1/r 2 deviations in the Solar System Current limits on additional Yukawa potential: α × (Newtonian-gravity) × e -r/ λ MoonLIGHT designed to provide accuracy of 100 µ m on the space segment (the CCR). Untested regions If the other error sources on LLR will improve with time at the same level then a MoonLIGHT CCR array will improve limits from ~10 -10 to 10 -12 at scales of 10 6 meters 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
APOLLO: Achieving the 1 mm Goal • APOLLO offers order-of-magnitude improvements (mm-level) to LLR by: – Using a 3.5 m telescope at a high elevation site (southern New Mexico) – Using a 16-element APD array – Operating at 20 Hz pulse rate – Multiplexed timing capable of detecting multiple photons per shot – Tight integration of experiment with analysis – Having a fund-grabbing acronym • APOLLO is jointly funded by the NSF and by NASA • Started operations in 2007 • Leader: Tom Murphy, UCSD 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Librations: the main limitation of 1 st gen. LLR APOLLO can “sense” the array size and orientation 2007.10.28 2007.10.29 2007.11.19 2007.11.20 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Lunar Librations 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
nd Gen. 2 nd Gen. Lunar Lunar Reflectors Reflectors 2 In the US: A LUNAR LASER RANGING RETRO-REFLECTOR ARRAY for the 21 st CENTURY LLRRA21 An Approved NASA Project “Lunar Sortie Scientific Opportunities” NASA Lunar Science Institute In Italy: Moon Laser Instrumentation for High-accuracy General relativity Tests Our PI, Doug Currie of UMD, is MoonLIGHT one of the inventors Mainly supported by INFN-LNF of LLR. S. Dell'Agnello In part supported by ASI for the Studies (LNF) is Co- PI “Observation of the Universe from the Moon” Phase A of the lunar mission “MAGIA” 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
MoonLIGHT 2G LLR: distributed, large CCRs Apollo 15: MoonLIGHT: distributed large (10cm) CCRs. ~ m 2 array of small CCRs Robotic (rover/lander) or manned deployment Background image courtesy of Lockheed Martin. Rover/lander image courtesy of NASA 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
1 st gen . Lunar 2 nd gen . Lunar Laser Ranging Laser Ranging Δ t t 2 1 unresolved pulse 3 separated back to Earth due t 1 pulses back to multi-CCR and to Earth t 3 librations New, single, big, Old Apollo 11 array sparse CCR array of 100, small CCRs Δ t t 3 t 2 t 1 time time Short Pulse to Moon Wide Pulse to Earth Pulse to Moon Pulses to Earth 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Geopolitically-free Network of 4 multi-site simultaneously operating instruments Core Instrument WG Results • Core Science/Instruments List – Seismology ILN Lander Node or – Heat Flow ESA Lander – E&M Sounding – Laser Ranging for Lunar Geodesy and Test for General Relativity • Note that all landing site activities will require geologic context (will require a Camera) 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Solid, uncoated CCR. Largest, most accurate ever: TECHNICAL CHALLENGES • Fabrication of the CCR to Required Tolerances (0.2”) • Sufficient Return for Reasonable Operation (single CCR) – Ideal Case for Link Equation • Thermal Distortion of Optical Performance (10 cm) – Absorption of Solar Radiation within the CCR – Mount Conductance - Between Housing and CCR – Pocket Radiation - Heat Exchange with Housing – Solar Breakthrough - Due to Failure of TIR • Stability of Lunar Surface Emplacement (100 to 1 micron) – Problem of Regolith Heating and Expansion – Drilling to Stable Layer for CCR Support – Thermal Blanket to Isolate Support – Housing Design to Minimize Thermal Expansion 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
SCF: Satellite/Lunar laser ranging Characterization Facility SCF-Test CCR Far Field Diffraction Pattern circuit CCRs inside or outside the SCF 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Big CCR Housing 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Big CCR Housing and Thermal Shields Temperature Probes on CCR’s back face Gold thermal shield Assembly in SCF Laser beam hit the CCR in SCF 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Temperature Probes on Big CCR We glued 3 Temperature Sensors along one of the back face of CCR Manganin wires RGW36 Low thermal conductivity Staycast 2850 + catalyst 9 35 mm 35 mm Sensors: Silicon Diode DT-470 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Started SCF-Testing on MoonLIGHT CCR Exempla….. Far Field Diffraction Pattern 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
Frascati 2 nd Generation LLR workshop photo March 25, 2010, outside the SCF lab, during 24x7 shifts for the SCF-Test of our 2 nd Generation “MoonLIGHT/LLRRA21” CCR Small photos: people absent, on SCF night shifts or training for a Space Shuttle flight… J. Battat T. Murphy (MIT) (UCSD) S. Dell’Agnello D. Currie G. Bianco LNF-INFN (UMD) (ASI) C. Luceri (e-Geos) R. Vittori 24-29 May 2010, Vulcano Marco Garattini (LNF-INFN)
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