Potential of salt-accumulating and salt-secreting halophytic plants for recycling sodium chloride in human urine in bioregenerative life support systems

This study addresses the possibility of growing different halophytic plants on mineralized human urine as a way to recycle NaCl from human wastes in a bioregenerative life support system (BLSS). Two halophytic plant species were studied: the salt-accumulating Salicornia europaea and the salt-secreting Limonium gmelinii. During the first two weeks, plants were grown on Knop’s solution, then an average daily amount of urine produced by one human, which had been preliminarily mineralized, was gradually added to the experimental solutions. Nutrient solutions simulating urine mineral composition were gradually added to control solutions. NaCl concentrations in the stock solutions added to the experimental and control solutions were 9 g/L in the first treatment and 20 g/L in the second treatment. The mineralized human urine showed some inhibitory effects on S. europaea and L. gmelinii. The biomass yield of experimental plants was lower than that of control ones. If calculated for the same time period (120 d) and area (1 m²), the amount of sodium chloride taken up by S. europaea plants would be 11.7 times larger than the amount taken up by L. gmelinii plants (486 g/m² vs. 41 g/m²). Thus, S. europaea is the better choice of halophyte for recycling sodium chloride from human wastes in BLSS.     

Science operations planning expertise: A neglected component of mission design

In this paper, Science Operations Planning Expertise (SOPE) is defined as the expertise that is held by people who have the two following qualities. First they have both theoretical and practical experience in operations planning, in general, and in space science operations planning in particular. Second, they can be used, on request and at least, to provide with advice the teams that design and implement science operations systems in order to optimise the performance and productivity of the mission. However, the relevance and use of such SOPE early on during the Mission Design Phase (MDP) is not sufficiently recognised. As a result, science operations planning is often neglected or poorly assessed during the mission definition phases. This can result in mission architectures that are not optimum in terms of cost and scientific returns, particularly for missions that require a significant amount of science operations planning. Consequently, science operations planning difficulties and cost underestimations are often realised only when it is too late to design and implement the most appropriate solutions. In addition, higher costs can potentially reduce both the number of new missions and the chances of existing ones to be extended. Moreover, the quality, and subsequently efficiency, of SOPE can vary greatly. This is why we also believe that the best possible type of SOPE requires a structure similar to the ones of existing bodies of expertise dedicated to the data processing such as the International Planetary Data Alliance (IPDA), the Space Physics Archive Search and Extract (SPASE) or the Planetary Data System (PDS). Indeed, this is the only way of efficiently identifying science operations planning issues and their solutions as well as of keeping track of them in order to apply them to new missions. Therefore, this paper advocates for the need to allocate resources in order to both optimise the use of SOPE early on during the MDP and to perform, at least, a feasibility study of such a more structured SOPE.     

Study of the variability of blazars gamma-ray emission

The γ-ray emission of blazar jets shows a pronounced variability and this feature provides limits to the size and to the speed of the emitting region. We study the γ-ray variability of bright blazars using data from the first 18 months of activity of the Large Area Telescope on the Fermi Gamma-Ray Space Telescope. From the daily light-curves of the blazars characterized by a remarkable activity, we firstly determine the minimum variability time-scale, giving an upper limit for the size of the emitting region of the sources, assumed to be spheroidal blobs in relativistic motion. These regions must be smaller than ∼10⁻³ parsec. Another interesting time-scale is the duration of the outbursts. We conclude that they cannot correspond to radiation produced by a single blob moving relativistically along the jet, but they are either the signature of emission from a standing shock extracting energy from a modulated jet, or the superposition of a number of flares occurring on a shorter time-scale. We also derive lower limits on the bulk Lorentz factor needed to make the emitting region transparent for gamma-rays interacting through photon–photon collisions.     

Automatic detection of geomagnetic sudden commencement via time–frequency clusters

One of global processes in ionosphere–thermosphere–magnetosphere system is the geomagnetic storms. It is of great importance to develop an algorithm that auto-detects sudden commencement because it could be an indicator of onset of the geomagnetic storm. Automatic detection of geomagnetic sudden commencement is based on time–frequency clusters generated by spectrogram. Proposed algorithm is tested on data set collected from stations belong to the international real-time magnetic observatory network (INTERMAGNET). Maximum standard deviation of algorithm detection times is observed to be one minute of the corresponding arrival times published by National Geophysical Data Center (NGDC).     

Gravity wave momentum flux generation close to mid-latitude Andes in mesoscale simulations of late 20th and 21st centuries

Adequate representations of diverse dynamical processes in general circulation models (GCM) are necessary to obtain reliable simulations of the present and the future. The parameterization of orographic gravity wave drag (GWD) is one of the critical components of GCM. It is therefore convenient to evaluate whether standard orographic GWD parameterizations are appropriate. One alternative is to study the generation of gravity waves (GW) with horizontal resolutions that are higher than those used in current GCM simulations. Here we assess the seasonal pattern of topographic GW momentum flux (GWMF) generation for the late 20th and 21st centuries in a downscaling using the Rossby Centre regional atmospheric model under the Intergovernmental Panel on Climate Change A1B emission conditions. We focus on one of the world’s strongest extra-tropical GW zones, the Andes Mountains at mid-latitudes in the Southern Hemisphere. The presence of two GCM sub-grid scale structures locally contributing to GWMF (one positive and one negative) is found to the East of the mountains. For the late 21st century the strength of these structures during the GW high season increases around 23% with respect to the late 20th century, but the GWMF average over GCM grid cell scales remains negative and nearly constant around −0.015 Pa. This constitutes a steady significant contribution during GW high season, which is not related to the GWMF released by individual sporadic strong GW events. This characteristic agrees with the fact that no statistically significant variation in GWMF at source level has been observed in recent GCM simulations of atmospheric change induced by increases in greenhouse gases.     

A feasibility study for the detection of the diurnal variation of tropospheric NO2 over Tokyo from a geostationary orbit

We have conducted a feasibility study for the geostationary monitoring of the diurnal variation of tropospheric NO₂ over Tokyo. Using NO₂ fields from a chemical transport model, synthetic spectra were created by a radiative transfer model, SCIATRAN, for summer and winter cases. We then performed a Differential Optical Absorption Spectroscopy (DOAS) analysis to retrieve NO₂ slant column densities (SCDs), and after converting SCDs into vertical column densities (VCDs), we estimated the precision of the retrieved VCDs. The simulation showed that signal-to-noise ratio (SNR) ? 500 is needed to detect the diurnal variation and that SNR ? 1000 is needed to observe the local minimum occurring in the early afternoon (LT13–14) in summer. In winter, the detection of the diurnal variation during LT08–15 needs SNR ? 500, and SNR ? 1000 is needed if early morning (LT07) and early evening (LT16) are included. The currently discussed sensor specification for the Japanese geostationary satellite project, GMAP-Asia, which has a horizontal resolution of 10 km and a temporal resolution of 1hr, has demonstrated the performance of a precision of several percent, which is approximately corresponding to SNR = 1000–2000 during daytime and SNR ? 500 in the morning and evening. We also discuss possible biases caused by the temperature dependence of the absorption cross section utilized in the DOAS retrieval, and the effect of uncertainties of surface albedo and clouds on the estimation of precisions.     

Seasonal variation of surface refractivity over Nigeria

The seasonal variation of surface refractivity over Nigeria was studied using two years in-situ meteorological data from eight locations over Nigeria. The result shows that the surface refractivity generally has higher value during rainy season than dry season at all location studied. The results also show that the value of surface refractivity increases from arid region in the north to the coastal area in south. The results also show that local meteorology plays a very important role in refractivity variation.     

Effect of matching between the magnetic field and channel length on the performance of low sputtering Hall thrusters

Discharge characteristics of a non-wall-loss Hall thruster were studied under different channel lengths using a design based on pushing a magnetic field through a double permanent magnet ring. The effect of different magnetic field intensities and channel lengths on ionization, efficiency, and plume divergence angle were studied. The experimental results show that propellant utilization is improved for optimal matching between the magnetic field and channel length. While matching the magnetic field and channel length, the ionization position of the neutral gas changes. The ion flow is effectively controlled, allowing the thrust force, specific impulse, and efficiency to be improved. Our study shows that the channel length is an important design parameter to consider for improving the performance of non-wall-loss Hall thrusters.     

Orbital stability close to asteroid 624 Hektor using the polyhedral model

We investigate the orbital stability close to the unique L4-point Jupiter binary Trojan asteroid 624 Hektor. The gravitational potential of 624 Hektor is calculated using the polyhedron model with observational data of 2038 faces and 1021 vertexes. Previous studies have presented three different density values for 624 Hektor. The equilibrium points in the gravitational potential of 624 Hektor with different density values have been studied in detail. There are five equilibrium points in the gravitational potential of 624 Hektor no matter the density value. The positions, Jacobian, eigenvalues, topological cases, stability, as well as the Hessian matrix of the equilibrium points are investigated. For the three different density values the number, topological cases, and the stability of the equilibrium points with different density values are the same. However, the positions of the equilibrium points vary with the density value of the asteroid 624 Hektor. The outer equilibrium points move away from the asteroid’s mass center when the density increases, and the inner equilibrium point moves close to the asteroid’s mass center when the density increases. There exist unstable periodic orbits near the surface of 624 Hektor. We calculated an orbit near the primary’s equatorial plane of this binary Trojan asteroid; the results indicate that the orbit remains stable after 28.8375?d.     

Application of small-size antennas for estimation of angles of arrival of HF signals scattered by ionospheric irregularities

A modification of the Doppler Interferometry Technique is suggested to enable estimating angles of arrival of comparatively broadband HF signals scattered by random irregularities of the ionospheric plasma with the use of small-size weakly directional antennas. The technique is based on the measurements of cross-spectra phases of the probe radiation recorded at least in three spatially separated points. The developed algorithm has been used to investigate the angular and frequency-time characteristics of HF signals propagating at frequencies above the maximum usable one (MUF) for the direct radio path Moscow-Kharkiv. The received signal spectra show presence of three families of spatial components attributed, respectively, to scattering by plasma irregularities near the middle point of the radio path, ground backscatter signals and scattering of the sounding signals by the intense plasma turbulence associated with auroral activations. It has been shown that the regions responsible for the formation of the third family components are located well inside the auroral oval. The drift velocity and direction of the auroral ionosphere plasma have been determined. The obtained estimates are consistent with the classical conception of the ionospheric plasma convection at high latitudes and do not contradict the results of investigations of the auroral ionosphere dynamics using the SuperDARN network.