Gravity, Geodesy and Fundamental Physics with BepiColombo’s MORE Investigation

open40siThe Mercury Orbiter Radio Science Experiment (MORE) of the ESA mission BepiColombo will provide an accurate estimation of Mercury’s gravity field and rotational state, improved tests of general relativity, and a novel deep space navigation system. The key experimental setup entails a highly stable, multi-frequency radio link in X and Ka band, enabling two-way range rate measurements of 3 micron/s at nearly all solar elongation angles. In addition, a high chip rate, pseudo-noise ranging system has already been tested at 1-2 cm accuracy. The tracking data will be used together with the measurements of the Italian Spring Accelerometer to provide a pseudo drag free environment for the data analysis. We summarize the existing literature published over the past years and report on the overall configuration of the experiment, its operations in cruise and at Mercury, and the expected scientific results.openIess L.; Asmar S.W.; Cappuccio P.; Cascioli G.; De Marchi F.; di Stefano I.; Genova A.; Ashby N.; Barriot J.P.; Bender P.; Benedetto C.; Border J.S.; Budnik F.; Ciarcia S.; Damour T.; Dehant V.; Di Achille G.; Di Ruscio A.; Fienga A.; Formaro R.; Klioner S.; Konopliv A.; Lemaitre A.; Longo F.; Mercolino M.; Mitri G.; Notaro V.; Olivieri A.; Paik M.; Palli A.; Schettino G.; Serra D.; Simone L.; Tommei G.; Tortora P.; Van Hoolst T.; Vokrouhlicky D.; Watkins M.; Wu X.; Zannoni M.Iess L.; Asmar S.W.; Cappuccio P.; Cascioli G.; De Marchi F.; di Stefano I.; Genova A.; Ashby N.; Barriot J.P.; Bender P.; Benedetto C.; Border J.S.; Budnik F.; Ciarcia S.; Damour T.; Dehant V.; Di Achille G.; Di Ruscio A.; Fienga A.; Formaro R.; Klioner S.; Konopliv A.; Lemaitre A.; Longo F.; Mercolino M.; Mitri G.; Notaro V.; Olivieri A.; Paik M.; Palli A.; Schettino G.; Serra D.; Simone L.; Tommei G.; Tortora P.; Van Hoolst T.; Vokrouhlicky D.; Watkins M.; Wu X.; Zannoni M

Proposed antimatter gravity measurement with an antihydrogen beam

The principle of the equivalence of gravitational and inertial mass is one of the cornerstones of general relativity. Considerable efforts have been made and are still being made to verify its validity. A quantum-mechanical formulation of gravity allows for non-Newtonian contributions to the force which might lead to a difference in the gravitational force on matter and antimatter. While it is widely expected that the gravitational interaction of matter and of antimatter should be identical, this assertion has never been tested experimentally. With the production of large amounts of cold antihydrogen at the CERN Antiproton Decelerator, such a test with neutral antimatter atoms has now become feasible. For this purpose, we have proposed to set up the AEGIS experiment at CERN/AD, whose primary goal will be the direct measurement of the Earth's gravitational acceleration on antihydrogen with a classical Moiré deflectometer. © 2007 Elsevier B.V. All rights reserved

Old workhorse of oxide investigations : new features of Co3O4

The electrochemical behaviour of Co3O4 from exhaustive cobalt nitrate decomposition (T = 260-850 \ub0C) is investigated on graphite-supported electrodes, mainly relying on quasi-reversible results. Two well defined 1-e- redox systems are observed related to Co2+/Co3+ and Co3+/Co4+ reactions of non-equivalent oxide surface sites. Oxide stoichiometry is directly estimated by voltammetry in `wet' conditions and depends on preparation temperature as in ex situ solid state data. Adsorption of surface intermediates involved in charge transfer is examined. Langmuir and Temkin-type adsorption isotherms are obeyed for the Co2+/Co3+ and Co3+/Co4+ redox systems, respectively. Unusually negative (attractive) lateral interaction parameters are calculated for the latter system. Separation of oxide and graphite currents is achieved to permit real electrode surface area determination

Anodic deposition of \u3b3-FeOOH layers on inert metal electrodes

The anodic oxidation of Fe2+ ions in neutral and alkaline solutions was studied by using a gold or platinum rotating disk electrode in the region of limiting currents. The reaction occurs with the quantitative deposition on the base metal of a ferric oxyhydroxide (\u3b3-FeOOH). The effects introduced by the different experimental variables on the limiting currents are reported. The kinetic contributions of the mass transport and of the subsequent reaction steps are individually examined. It is proposed that the reaction scheme involves the coupling of two diffusion steps occurring in solution within the Levich layer and across the thickness of the deposited oxide. These two reaction steps are kinetically connected by the ion transport of Fe2+ ions across the interfacial potential difference; this latter reaction step is considered to introduce the pH dependence of the overall reaction. \ua9 1983

Hydrothermal preparation of goethite crystals

The precipitation of goethite particles by a hydrothermal procedure is described. The reaction involves the oxidation of ferrous ion solutions with hydroxylamine salts at 85 \ub0C. The phase purity of the oxide is discussed as a function of the solution composition, and in particular of the pH and of the different anions. Scanning electron microscope examinations show that goethite particles are acicular crystals with a rather narrow size distribution. The crystals show prismatic shape and appear to be elongated in the [001] crystallographic direction. The attribution of 110 form to the side faces of the prisms is proposed. \ua9 1985

Composition and diffusion properties of \u3b3-FeOOH deposited in sulphate solutions

\u3b3-FeOOH layers have been deposited by electrochemical oxidation of Fe2+ in 0.25 M Na2SO4. Results show that the bulk properties of the oxide, as represented by the diffusion coefficient of a process occurring across the layers during the oxide growth, undergo strong variations with increasing the oxide thickness. AES depth profiles of the samples show that sulphate is incorporated in the layers with a thickness dependent concentration. The diffusion coefficient of the sulphate-rich part of the layer is comparatively lower than the one of the sulphate depleted oxide. \ua9 1988

Cobalt(II) adsorption on haematite at room temperature

The interactions of Co2+ with haematite are investigated as a function of the solution pH by means of acid-base titrations and direct adsorption measurements. Adsorption determinations show that Co2+ is adsorbed on haematite to increasing extents with increasing solution pH. The desorption of Co2+ from haematite is also found to be a function of pH as Co2+ can be desorbed on acidification of the solution; however, the adsorption is never fully reversible. From acid-base titrations the adsorption of Co2+ appears to modify the primary H+-OH- adsorption equilibria of the oxide surface. \ua9 1983

Oxide electrodes. A new technique to bind oxide powders onto Au substrates

A technique is described to obtain supported oxide powder electrodes. Preformed powders are first embedded into a gold substrate, as reported by Totir et al. and then made to adhere in place by heating at T .apprx. 260-300\ub0C in flowing oxygen. This latter step is of the greatest importance to obtain reliable electrodes for use in aq. electrolytes. Electrode stability and reproducibility are examd. on voltammetric and O2 evolution results using Co3O4 as a sensitive test oxide material. Many independent Au-Co3O4 electrodes compare favorably with one another and with graphite-supported electrodes from an unrelated, room temp. binding technique. Substrate and oxide-substrate junction effects are minimized