MoonLIGHT: (Moon Laser Instrumentation for General relativity High-accuracy Tests) A LUNAR LASER RANGING ARRAY FOR THE 21ST CENTURY

D. G. Currie (PI), University of Maryland at College Park, MD, USA G. Bellettini, C. Cantone, S. Dell’Agnello (Co-PI), G. O. Delle Monache, M. Garattini, N. Intaglietta, INFN-LNF, Laboratori Nazionali di Frascati dell’INFN, Frascati (Rome), ITALY R. Vittori, Aeronautica Militare Italiana, Rome, ITALY Collaboration with the ASI - Matera Lunar Ranging Observatory (G. Bianco et al), Matera, ITALY T. Murphy, University of California at San Diego, CA, USA D. Carrier, Lunar GeoTechnical Institute, Lakeland, Florida, USA D. Rubincam, NASA/GSFC, Greenbelt, MD, USA A. Hajian, U. S. Naval Observatory, Washington DC, USA MoonLIGHT

ITALY-US collaborative proposal for improving by a factor up to 1000 the accuracy of the current Lunar Laser Ranging (LLR) experiment done with retro-reflector arrays deployed on the Moon by the Apollo 11, 14 and 15 missions.

This requires a modified thermal, optical and mechanical design of the array and space-climatic tests at the LNF Space Climatic Facility. MoonLIGHT will allow a rich program of accurate tests of General Relativity already with current laser ranging systems, like ASI-MLRO and APOLLO. This accuracy will get better and better as laser performance improves over the next few decades, like it did since the ‘60s.

For the construction and installation of the mechanic structures and the “suitcase” there is window of opportunity for industries.

Moriond Gravitation, March 2007 M. Garattini, INFN-LNF (Frascati) 2 ASI study vs NASA proposal • NASA call Suitcase science to the Moon: submitted manned version, “MoonLIGHT-M” – Passive experiment only – NASA decision expected by end of spring 2007 – LNF work at zero cost to NASA – NASA funds include hardware to be tested at LNF • ASI study: robotic version, “MoonLIGHT-R” – To be combined w/one Optical clock (G. Tino et al) – Within the study MoonLIGHT-R has priority “1A” – To be followed by Phase-A study. • LNF will do climatic tests on NASA retro-reflectors and is doing now climatic simulations

Moriond Gravitation, March 2007 M. Garattini, INFN-LNF (Frascati) 3 Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) S

APOLLO 11, 14,15 L R

LAGEOS: a ~ 12000 Km

• Started in 1969 by Currie et al. • Currie is the MoonLIGHT PI. • LAGEOS II (NASA-ASI), 1992, has an orbit accuracy < 1 cm General Relativity Science Objectives (for up to factor 100 improvement of LLR)

PPN parameter β Parameter α (see next slide) Limits on non-Newtonian gravity Current limits on non-Newtonian gravity, as additional Yukawa potential: α × (Newtonian-gravity) × e-r/λ

With MoonLIGHT current limit on α will be 10-12 for a ranging accuracy of 100 µm

The red arrows indicate untested regions “String” Model Beyond General Relativity

• This specific (mem)“Brane” World theory gives an anomalous precession of the Moon of ~ 1 mm, in addition to GR • LLR accuracy now is ~ 1 cm. This model can be tested with factor 100 improvement over current LLR 532 nm Laser pulse LLRA_20th from the Earth LLRA_21st

Affected by “geometric” libration Unaffected by “geometric” libration of the Moon of the Moon (limits LLR accuracy to ~ cm value)

~ 30 cm × 30 cm matrix array ≤ 100 m × 100 m sparse array 1 pulse back to Earth 3 pulses back to Earth

T3 < T2 < T1 ΔT T2

T1 T3

LLRA_20th LLRA_21st

ΔT time T3 T2 T1 time Pulse to Moon Pulse back to Earth Pulse to Moon Pulses back to Earth The MoonLIGHT Array

• Distance among CCRs ? To be optimized; ~ 20 m • Pattern of CCR positions ? Sparse in an area ~ 100 x 100 m • Positioning accuracy ? ~ 1 m • Inclination ? For ex. 30o degrees but depends on landing site • Inclination accuracy ? Few degrees • Pointing to Earth ? Few degrees • CCR diameter ? ~ 10 cm • Length of support foot ? Few cm • Number of CCRs ? 8 CCRs (< 10 Kg weight)

Moriond Gravitation, March 2007 M. Garattini, INFN-LNF (Frascati) 10 Retro-reflector in a box (manned mission design by Vittori) Retro-reflector: 10 cm diam. Suitcase for the boxes Box: 14 cm diameter (dimensions in mm)

Metal: INVAR or ULE

Moriond Gravitation, March 2007 M. Garattini, INFN-LNF (Frascati) 11 Installation on the Moon

Innermost layer: high VISIBLE reflectivity high IR absorptivity

Outermost layer: somewhat low VIS. absorptivity low IR absorptivity; perhaps gold 30o Multi-Layer Insulations

REGOLITH

“Foot” fixed in a hole drilled on the isothermal Top surface: low VISIBLE absorption; rock (about ± 2 K) BELOW 50 cm of regolith high 10 µm emissivity

Moriond Gravitation, March 2007 M. Garattini, INFN-LNF (Frascati) 12 Frascati Space Climatic Facility

Moriond Gravitation, March 2007 M. Garattini, INFN-LNF (Frascati) 13 Effect of space climatic conditions on (Al) box and retro-reflector temperatures (thermal simulation)

T(center) = 142.9 K

T(tip) = 141.0 K CCR Optical characterization at LNF

Far-Field Diffraction Pattern (FFDP) of single CCR return with laser

• “Optical FLAT” (mirror) for normalization

• 2 CCDs as laser profilers. Readout by PC via firewire Repeat with CCR inside the Space Climatic Facility

Moriond Gravitation, March 2007 M. Garattini, INFN-LNF (Frascati) 15 Conclusions • Well defined goals of fundamental physics – General Relativity – String (mem)Brane World model • “The accelerated universe and the Moon” (modified Gravity) • First-pass design of the payload complete (including preliminary thermal studies by LNF) • Thermal and laser tests to be done at the Frascati Space Climatic Facility • Industrial Partners – mechanics and installation • Possible synergic effort with NASA – Manned version of MoonLIGHT

Moriond Gravitation, March 2007 M. Garattini, INFN-LNF (Frascati) 16