Jinsong Ping

Determination of the free lunar libration modes from ephemeris DE430

The Moon’s physical librations have been extensively studied, and elaborate researches have been developed for the purpose of deriving accurate modes of free librations. Our motivation comes from the Planetary and Lunar Ephemeris DE430 by JPL/NASA, which was created in April 2013, and is reported to be the most accurate lunar ephemeris today using the data from Gravity Recovery and Interior Laboratory (GRAIL). Therefore, the residuals after fitting the model have reduced owing to improvement in the libration models, and the free librations embedded in the Euler angles have also improved. We use Fourier analysis to extract the approximate frequencies from DE430 and then a quadratic interpolation method is used to determine higher accuracy frequencies. With the frequencies, the linear least-squares fitting method is employed to fit the lunar physical librations to DE430. From this analysis we identified the three modes of free physical librations, and estimated the amplitudes as 1.471′′ in longitude, 0.025′′ in latitude and 8.19′′ × 3.31′′ for the wobble, with the respective periods of 1056.16, 8806.9 and 27262.99 d. Since the free librations damp with time, they require recent excitation or a continuous stimulating mechanism in order to sustain.

Chang’e 3 lunar mission and upper limit on stochastic background of gravitational wave around the 0.01 Hz band

Abstract The Doppler tracking data of the Chang’e 3 lunar mission is used to constrain the stochastic background of gravitational wave in cosmology within the 1xa0mHz to 0.05xa0Hz frequency band. Our result improves on the upper bound on the energy density of the stochastic background of gravitational wave in the 0.02–0.05xa0Hz band obtained by the Apollo missions, with the improvement reaching almost one order of magnitude at around 0.05xa0Hz. Detailed noise analysis of the Doppler tracking data is also presented, with the prospect that these noise sources will be mitigated in future Chinese deep space missions. A feasibility study is also undertaken to understand the scientific capability of the Chang’e 4 mission, due to be launched in 2018, in relation to the stochastic gravitational wave background around 0.01xa0Hz. The study indicates that the upper bound on the energy density may be further improved by another order of magnitude from the Chang’e 3 mission, which will fill the gap in the frequency band from 0.02xa0Hz to 0.1xa0Hz in the foreseeable future.

Ionospheric inversion of the Venus Express radio occultation data observed by Shanghai 25 m and New Norcia 35 m antennas

Electron density profiles of the Venus ionosphere are inverted from the Venus Express (VEX) one-way open-loop radio occultation experiments carried out by Shanghai 25 m antenna from November 2011 to January 2012 at solar maximum conditions and by New Norcia 35 m antenna from August 2006 to June 2008 at solar intermediate conditions. The electron density profile (from 110 km to 400 km) retrieved from the X-band egress observation at Shanghai station, shows a single peak near 147 km with a peak density of about

DETERMINATION OF THE EXTRAGALACTIC-PLANETARY FRAME TIE FROM EARTH ORIENTATION PARAMETERS

2 times 10^4 rm{cm}^{-3}

Lunar topographic model CLTM-s01 from Chang'E-1 laser altimeter

at a solar zenith angle of 94

Working models for the gravitational field of Phobos

^{circ}

Relative position determination of a lunar rover using high-accuracy multi-frequency same-beam VLBI

. As a comparison, the VEX radio science (VeRa) observations at New Norcia station were also examined, including S-, X-band and dual-frequency data in the ingress mode. The results show that the electron density profiles retrieved from the S-band data are more analogous to the dual-frequency data in the profile shape, compared with the X-band data. Generally, the S-band results slightly underestimate the magnitude of the peak density, while the X-band results overestimate that. The discrepancy in the X-band profile is probably due to the relatively larger unmodeled orbital errors. It is also expected that the ionopause height is sensitive to the solar wind dynamical pressure in high and intermediate solar activities, usually in the range of 200 km - 1000 km on the dayside and much higher on the nightside. Structural variations (bulges and fluctuations) can be found in the electron density profiles in intermediate solar activity, which may be caused by the interaction of the solar wind with the ionosphere. Considerable ionizations can be observed in the Venus nightside ionosphere, which are unexpected for the Martian nightside ionosphere in most cases.

Comparison analyses on the 150 × 150 lunar gravity field models by gravity/topography admittance, correlation and precision orbit determination

PRLSENTLY there are three kinds of realization of conventional celestial reference frames (CCRFs), i. e. the optical frame, the planetary frame and the extragalactic radio frame. Though the CCRFs are high in precision, due to the difference in (ⅰ) the constants, parameters, formulae and force models used to define the frames; (ⅱ) the methods and techniques of