Lunar Laser Ranging Analysis Report

**J.G. Williams, D.H. Boggs, J.O. Dickey, and J.T. Ratcliff**

##### Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA

#### Introduction/Background/Data Products Provided:

Analyses of laser ranges to the Moon are used for a variety of
investigations: lunar science, gravitational physics, geodesy,
geodynamics and astronomy. Unique contributions from LLR include:
detection of a molten lunar core; measurement of tidal dissipation in
the Moon; an accurate test of the principle of equivalence for massive
bodies (strong equivalence principle); and detection of lunar free
librations. LLR analyses provide tests of gravitational physics,
measurements of the Moon\'s tidal acceleration and the Earth\'s rotation
and precession, and orders-of-magnitude improvements in the accuracies
of the lunar ephemeris and three-dimensional rotation. Lunar and
planetary ephemerides and lunar physical librations are available to the
scientific community at <http://ssd.jpl.nasa.gov/horizons.html>.

**Current Activities:**

Lunar Laser Ranges are regularly received from the Observatoire de la
Côte d\'Azur and McDonald Observatory sites. These ranges are processed
at regular intervals for Earth rotation information. UT0 and variation
of latitude for the two stations are input to the JPL Earth rotation
filter.

The tidal acceleration of the Moon has been computed for several
ephemerides based on iterated solutions. The acceleration in mean
longitude due to dissipative effects is -25.7 \"/cent2, of which -26.0
\"/cent2 is due to tides on Earth and +0.3 \"/cent2 is due to tidal and
fluid core dissipation in the Moon. The tidal increase in semimajor axis
is 38 mm/yr.

Dissipation in the Moon is discussed in (4). The solid-body tidal Q is
low and a fluid core is detected. An oblate core-mantle boundary will
influence the determination of the Love number k2. First attempts
allowing for CMB oblateness give k2=0.026, with uncertainty 0.003 (6,
7).

Uncertainties continue to tighten for tests of gravitational physics.
The Earth and Moon are accelerated alike in the Sun\'s gravitational
field to 1.5 parts in 1013 (1). This equivalence principle test is
sensitive to differences between Earth and Moon due to both composition
and self-energy. The relativistic geodetic precession of 19 mas/yr is
confirmed within 0.35%. Based on point mass interactions, the
uncertainties for Parameterized Post Newtonian beta and gamma are both
0.004 (2). The equivalence principle test limits the beta uncertainty
further to 0.0005 (1). The gravitational constant G has no detectible
rate for dG/dt / G within 1.1x10-12 /yr (2, 8).

*Papers*

1\) J. D. Anderson and J. G. Williams, Long-Range Tests of the
Equivalence Principle, Classical and Quantum Gravity, vol. 18, in press,
2001.

2\) J. G. Williams, D. H. Boggs, and J. O. Dickey, Lunar Laser Tests of
Gravitational Physics, Proceedings of Ninth Marcel Grossmann Meeting
(World Scientific Publ.), in press, 2001, there is a short print version
and a longer electronic version.

3\) P. J. Shelus, J. G. Ries, J. G. Williams, and J. O. Dickey, A
Summary of LLR Activities and Science Results, Proceedings of 12th
International Workshop on Laser Ranging, Matera, Italy, November 2000,
in press, 2001.

4\) J. G. Williams, D. H. Boggs, C. F. Yoder, J. T. Ratcliff, and J. O.
Dickey, Lunar Rotational Dissipation in Solid Body and Molten Core,
submitted to J. Geophys. Res. - Planets, under revision, 2001.

###### Abstracts

5\) J. G. Williams,, D. H. Boggs, J. O. Dickey, and W. M. Folkner, Lunar
Laser Tests of Gravitational Physics, Marcel Grossmann IX, July 2-8,
2000, Rome, Italy.

6\) J. G. Williams, D. H. Boggs, J. T. Ratcliff, C. F. Yoder and J. O.
Dickey, The Moon\'s Molten Core, Tides, and Energy Dissipation, Abstract
for Division of Planetary Sciences, October 23-27, 2000, Pasadena, CA,
Bull. Amer. Astron. Soc. 32, 1034, 2000.

7\) J. G. Williams, D. H. Boggs, J. T. Ratcliff, C. F. Yoder and J. O.
Dickey, Influence of a Fluid Lunar Core on the Moon\'s Orientation,
Abstracts of the Lunar and Planetary Science Conference XXXII, abstract
#2028, March 12-16, 2001.

8\) J. G. Williams, J. D. Anderson, D. H. Boggs, E. L. Lau, and J. O.
Dickey, Solar System Tests for Changing Gravity, Amer. Astron. Soc.,
Pasadena, CA, June 3-7, 2001, Bulletin of the American Astronomical
Society, Vol. 33, 836, 2001.

**Key Points of Contact:**

[Name]{.underline} [e-mail]{.underline} [Telephone No.]{.underline}

James G. Williams <James.G.Williams@jpl.nasa.gov> (818) 354-6466

Dale H. Boggs <Dale.H.Boggs@jpl.nasa.gov> (818) 354-1630

Jean O. Dickey <Jean.O.Dickey@jpl.nasa.gov> (818) 354-3235

J. Todd Ratcliff <James.T.Ratcliff@jpl.nasa.gov> (818) 354-0204

All Key Points of Contact can be reached at:

Jet Propulsion Laboratory

Mail Stop 238-332

4800 Oak Grove Drive

Pasadena, CA 91109-8099

FAX: (818) 393-6890

**Future Plans:**

Continue investigation of lunar science and gravitational physics
utilizing LLR data. Generate Earth rotation results. Continue lunar
ephemeris and physical libration developments.