Spacecraft VLBI and Doppler tracking: algorithms and implementation

We present the results of several multi-station Very Long Baseline Interferometry (VLBI) experiments conducted with the ESA spacecraft Venus Express as a target. To determine the true capabilities of VLBI tracking for future planetary missions in the solar system, it is necessary to demonstrate the accuracy of the method for existing operational spacecraft. We describe the software pipeline for the processing of phase referencing near-field VLBI observations and present results of the ESA Venus Express spacecraft observing campaign conducted in 2010-2011. We show that a highly accurate determination of spacecraft state-vectors is achievable with our method. The consistency of the positions indicates that an internal rms accuracy of 0.1 mas has been achieved. However, systematic effects produce offsets up to 1 mas, but can be reduced by better modelling of the troposphere and ionosphere and closer target-calibrator configurations.Comment: 10 pages, 10 figures. Astronomy and Astrophysics, accepte

Structure alteration of a sandy-clay soil by biochar amendments

The aim of the present study was to investigate structure alterations of a sandy-clay soil upon addition of different amounts of biochar (f (bc) ). All the f (bc) samples were analyzed by high energy moisture characteristic (HEMC) technique and H-1 nuclear magnetic resonance (NMR) relaxometry. HEMC was applied in order to evaluate aggregate stability of biochar-amended soil samples. H-1 NMR relaxometry experiments were conducted for the evaluation of the pore distributions through the investigation of water dynamics of the same samples. The HEMC technique revealed improvement in aggregate stability through measurements of the amount of drainable pores and the stability ratio. The latter increased as the amount of biochar was raised up. The H-1 NMR relaxometry revealed a unimodal T (1) distribution for both the sole sandy-clay soil and the biochar. Conversely, a bimodal T (1) distribution was acquired for all the different f (bc) samples. Improvement in aggregate stability was obtained as biochar was progressively added to the sandy-clay soil. A dual mechanism of water retention has been hypothesized. In particular, intra-aggregate porosity was indicated as the main responsible for molecular water diffusion when f (bc) comprised between 0 and 0.33. Conversely, inter-aggregate porosity resulted predominant, through swelling processes, when f (bc) overcame 0.33

Regeneration of cellulose by water addition to phosphoric acid/cellulose mixture

In the last years, phosphoric acid has been increasingly considered as a simple and economic solvent for cellulose pretreatment before its degradation to glucose. Cellulose swells in 71–80% phosphoric acid solutions, whereas at higher H3PO4 concentrations dissolution appears to occur. In addition, it is reported that regenerated cellulose is more easily fermentable to bioethanol. The aim of the present study was to elucidate the mechanism for cellulose regeneration following treatment with phosphoric acid at room temperature. CPMAS 13C NMR spectra revealed a downfield shift of the 13C NMR signals from the regenerated cellulose as compared to the crystalline one. CPMAS 31P NMR spectroscopy showed presence of organic phosphate in the regenerated cellulose. These results suggested that cellulose regeneration consisted in the precipitation of a phosphorylated polymer. Fast field cycling NMR relaxometry confirmed such hypothesis. In fact, the correlation time of water saturated crystalline cellulose was shorter than that measured for the water saturated regenerated cellulose. The phosphate groups bound to the regenerated cellulose surface allow restriction of water mobility, thereby producing longer correlation times. Finally turbidimetric analyses revealed that the mechanism of regeneration consisted in a first reduction of the colloidal cellulose size followed by aggregation, colloidal size increment and flocculation. This study is of paramount importance to understand how phosphoric acid interact with cellulose in order to address its possible uses in biomass transformation for bioenergy purposes

First Results of Venus Express Spacecraft Observations with Wettzell

The ESA Venus Express spacecraft was observed at X-band with the Wettzell radio telescope in October-December 2009 in the framework of an assessment study of the possible contribution of the European VLBI Network to the upcoming ESA deep space missions. A major goal of these observations was to develop and test the scheduling, data capture, transfer, processing, and analysis pipeline. Recorded data were transferred from Wettzell to Metsahovi for processing, and the processed data were sent from Mets ahovi to JIVE for analysis. A turnover time of 24 hours from observations to analysis results was achieved. The high dynamic range of the detections allowed us to achieve a milliHz level of spectral resolution accuracy and to extract the phase of the spacecraft signal carrier line. Several physical parameters can be determined from these observational results with more observational data collected. Among other important results, the measured phase fluctuations of the carrier line at different time scales can be used to determine the influence of the solar wind plasma density fluctuations on the accuracy of the astrometric VLBI observations

EVALUATION OF INORGANIC CONTAMINANT REMOVAL FROM AQUEOUS SOLUTIONS USING PYROLIZED CHICKEN MANURE, CONIFER AND POPLAR WOOD AS ADSORBENT

Anthropogenic activities alter the natural flow of materials and introduce novel chemicals into the environment thereby causing serious soil and water pollution. Indeed, many industries produce aqueous effluents containing toxic substances, especially heavymetals. The presence of these contaminants in the environment is a great issue because of their toxicityand bioaccumulation ability which affect human life and the environment. Various physicochemical and biological techniques have been used to remove the heavy metals from waste waters, including chemical precipitation, ion exchange, chemical coagulation, electrolytic methods, membrane processes, and adsorption. Biochar is a carbonaceous material obtained from the pyrolysis of plant and animal biomasses. Due to its high porosity, it could be a potential alternative to the existing conventional technologies for the removal and/or recovery of metal ions from aqueous solutions. The aim of this work was the chemical-physical characterization of biochar produced from chicken manure (CM), conifers and poplar wood wastes in order to assess their ability in the removal of heavy metal from aqueous solutions. Chemical-physical characterization of the different CM chars was conducted by cross polarization magic angle spinning (CPMAS) 13 C NMR spectroscopy and NMR relaxometry together with a comparative study between the removal efficiencies of Cu(II), Ni(II) andPb(II) from synthetic wastewater by using adsorption onto biochars surfaces. From adsorption studies, it was observed that conifer biochar did not significantly adsorbed metals. This behavior is probably due to his own chemical characteristics, since it’s quite hydrophobic and probably its surface lacks functional groups able to bind ions. Conversely, chicken manure biochar proved to have the highest removal efficiencies for all the metals considered, in the order Pb(II)>Cu(II)>Ni(II) ions. In conclusion, different chars have different physicochemical characteristics so they should be addressed to different uses. For example, conifer char should not be used for remediation since it’s not effective in removing inorganic metals from aqueous solutions. The most effective in remediation was chicken manure biochar, probably thanks to the presence of nitrogen on its surface. In fact, nitrogen has a free electronic doublet/pair able to interact with cation. Finally, char metals absorption involves both a physical and a chemical mechanism and further studies should be addressed to explain it