Gravitational perturbations on local experiments in a satellite : The dragging of inertial frame in the HYPER project

We consider a nearly free falling Earth satellite where atomic wave interferometers are tied to a telescope pointing towards a faraway star. They measure the acceleration and the rotation relatively to the local inertial frame. We calculate the rotation of the telescope due to the aberrations and the deflection of the light in the gravitational field of the Earth. We show that the deflection due to the quadrupolar momentum of the gravity is not negligible if one wants to observe the Lense-Thirring effect of the Earth. We consider some perturbation to the ideal device and we discuss the orders of magnitude of the phase shifts due to the residual tidal gravitational field in the satellite and we exhibit the terms which must be taken into account to calculate and interpret the full signal. Within the framework of a geometric model, we calculate the various periodic components of the signal which must be analyzed to detect the Lense-Tirring effect. We discuss the results which support a reasonable optimism. As a conclusion we put forward the necessity of a more complete, realistic and powerful model in order to obtain a final conclusion on the theoretical feasibility of the experiment as far as the observation of the Lense-Thirring effect is involved.Comment: Accepted in GRG (vol 36, Feb 2004

Tidal gravitational effects in a satellite

Atomic wave interferometers are tied to a telescope pointing towards a faraway star in a nearly free falling satellite. Such a device is sensitive to the acceleration and the rotation relatively to the local inertial frame and to the tidal gravitational effects too. We calculate the rotation of the telescope due to the aberration and the deflection of the light in the gravitational field of a central mass (the Earth and Jupiter). Within the framework of a general parametrized description of the problem, we discuss the contributions which must be taken into account in order to observe the Lense-Thirring effect. Using a geometrical model, we consider some perturbations to the idealized device and we calculate the corresponding effect on the periodic components of the signal. Some improvements in the knowledge of the gravitational field are still necessary as well as an increase of the experimental capabilities; however our conclusions support a reasonable optimism for the future. Finally we put forward the necessity of a more complete, realistic and powerful model in order to obtain a definitive conclusion on the feasibility of the experiment as far as the observation of the Lense-Thirring effect is involved.Comment: accepted to General Relativity and Gravitatio

Passive scalar intermittency in low temperature helium flows

We report new measurements of turbulent mixing of temperature fluctuations in a low temperature helium gas experiment, spanning a range of microscale Reynolds number, $R_{\lambda}$, from 100 to 650. The exponents $\xi_{n}$ of the temperature structure functions $\sim r^{\xi_{n}}$ are shown to saturate to $\xi_{\infty} \simeq 1.45 \pm 0.1$ for the highest orders, $n \sim 10$. This saturation is a signature of statistics dominated by front-like structures, the cliffs. Statistics of the cliff characteristics are performed, particularly their width are shown to scale as the Kolmogorov length scale.Comment: 4 pages, with 4 figure