30 research outputs found
Analyzing shell structure from Babylonian and modern times
We investigate ``shell structure'' from Babylonian times: periodicities and
beats in computer-simulated lunar data corresponding to those observed by
Babylonian scribes some 2500 years ago. We discuss the mathematical similarity
between the Babylonians' recently reconstructed method of determining one of
the periods of the moon with modern Fourier analysis and the interpretation of
shell structure in finite fermion systems (nuclei, metal clusters, quantum
dots) in terms of classical closed or periodic orbits.Comment: LaTeX2e, 13pp, 8 figs; contribution to 10th Nuclear Physics Workshop
"Marie and Pierre Curie", 24 - 28 Sept. 2003, Kazimierz Dolny (Poland); final
version accepted for J. Mod. Phys.
Advancing Tests of Relativistic Gravity via Laser Ranging to Phobos
Phobos Laser Ranging (PLR) is a concept for a space mission designed to
advance tests of relativistic gravity in the solar system. PLR's primary
objective is to measure the curvature of space around the Sun, represented by
the Eddington parameter , with an accuracy of two parts in ,
thereby improving today's best result by two orders of magnitude. Other mission
goals include measurements of the time-rate-of-change of the gravitational
constant, and of the gravitational inverse square law at 1.5 AU
distances--with up to two orders-of-magnitude improvement for each. The science
parameters will be estimated using laser ranging measurements of the distance
between an Earth station and an active laser transponder on Phobos capable of
reaching mm-level range resolution. A transponder on Phobos sending 0.25 mJ, 10
ps pulses at 1 kHz, and receiving asynchronous 1 kHz pulses from earth via a 12
cm aperture will permit links that even at maximum range will exceed a photon
per second. A total measurement precision of 50 ps demands a few hundred
photons to average to 1 mm (3.3 ps) range precision. Existing satellite laser
ranging (SLR) facilities--with appropriate augmentation--may be able to
participate in PLR. Since Phobos' orbital period is about 8 hours, each
observatory is guaranteed visibility of the Phobos instrument every Earth day.
Given the current technology readiness level, PLR could be started in 2011 for
launch in 2016 for 3 years of science operations. We discuss the PLR's science
objectives, instrument, and mission design. We also present the details of
science simulations performed to support the mission's primary objectives.Comment: 25 pages, 10 figures, 9 table
A new determination of lunar orbital parameters, precession constant and tidal acceleration from LLR measurements
An analysis of Lunar Laser Ranging (LLR) observations from January 1972 until
April 2001 has been performed, and a new solution for the lunar orbital motion
and librations has been constructed that has been named S2001.
With respect to prior solutions, improvements in the statistical treatment of
the data, new nutation and libration models and the addition of the positions
of the observing stations to the list of fitted parameters have been introduced.
Globally, for recent observations, our rms (root mean square error) is within
2 to 3 centimeters in the lunar distance.
Special attention has been paid to the determination of the correction to
the IAU76 luni-solar constant of precession, and the value of the secular
acceleration of the Moon's longitude due to the tidal forces.
The main results are: –  correction to the constant of precession:
= -0.302 ±
, –  tidal acceleration of the lunar longitude:
Γ = -25.858 ±
.
The positions and velocities of the stations have also been determined.
The results are consistent with the ITRF2000 determinations from SLR
observations.
The lunar theory ELP is referred to a dynamical system and introduces the
inertial mean ecliptic of J2000.0.
The positioning of the reference system
of the theory with respect to ICRS is performed (and also with respect to some
useful JPL numerical integrations).
Finally the orientation of the celestial axes with respect to the ICRS
reference system has been derived as well as the offsets of the Celestial
Ephemeris Pole