Gradient generation for parametric control models

This paper presents a numerical method for approximating the solution of complex optimal control problems by a constrained function minimization problem in a finite dimensional space. This end is achieved by approximating only the control functions by a finite set of parameters. The computation of gradients with respect to the parameters modeling the control is explored in depth. A hybrid technique combining the rapid gradient generation capability of the method of gradients with the rapid convergence characteristics of finite-dimensional, variable-metric function minimization algorithms is presented. An algorithm for mapping the impulsive response gradient trajectory generated by the method of gradients into a gradient vector of the performance index with respect to the parameters modeling the control function is presented. The class of local parameterizations is shown to have a distinct computational advantage, from a gradient generation point of view, over the class of continuous polynomial approximations. Detailed results are presented for piecewise linear parametric control models. An algebraic transformation is presented for improving inaccurate gradients generated by a widespread computer implementation of the method of gradients.     

Early nucleosynthesis: The present situation

The most recent developments in the very light element abundance observations, especially the determination of a high (D/H) ratio 3 10^–4 on a remote QSO line of sight, are analyzed and some of the consequences on the Big Bang nucleosynthesis (BBN) models, on the predicted baryonic density and on the galactic evolution schemes are reviewed. Should this (D/H) determination be confirmed by further observations, the simplest standard BBN model would be the most successful in these abundance predictions: the baryon density should be close to the luminous mass density ^B (5–8)10^–3 if H=100 km s^–1 Mpc^–1; the challenge is now to devise galactic evolution models able to account for a large D destruction and avoiding to overproduce³He and metals.     

Survival of spores of the UV-resistant Bacillus subtilis strain MW01 after exposure to low-earth orbit and simulated martian conditions: data from the space experiment ADAPT on EXPOSE-E

In the space experiment "Molecular adaptation strategies of microorganisms to different space and planetary UV climate conditions" (ADAPT), bacterial endospores of the highly UV-resistant Bacillus subtilis strain MW01 were exposed to low-Earth orbit (LEO) and simulated martian surface conditions for 559 days on board the European Space Agency's exposure facility EXPOSE-E, mounted outside the International Space Station. The survival of B. subtilis MW01 spores from both assays (LEO and simulated martian conditions) was determined by a colony-formation assay after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110?nm) as well as the martian UV spectrum (λ≥200?nm) was the most deleterious factor applied; in some samples only a few spore survivors were recovered from B. subtilis MW01 spores exposed in monolayers. However, if shielded from solar irradiation, about 8% of MW01 spores survived in LEO conditions, and 100% survived in simulated martian conditions, compared to the laboratory controls. The results demonstrate the effect of shielding against the high inactivation potential of extraterrestrial solar UV radiation, which limits the chances of survival of even the highly UV-resistant strain of B. subtilis MW01 in the harsh environments of outer space and the martian surface.     

Sq(H) field variations at Sonmiani geomagnetic observatory,Pakistan for solar cycle 24

In this study, Sq(H) field results for Sonmiani geomagnetic observatory (SON), Pakistan are presented first time for solar cycle i.e., Solar Cycle 24. Sonmiani observatory was established in 2008 and was included in the list of INTERMAGNET Magnetic Observatory (IMO) in 2012. The analysis of Sq(H) field is performed to examine diurnal, annual and seasonal behaviour of Sq(H) field at Sonmiani along with Honolulu which is used as reference observatory. Both the observatories lie at the Equatorial Ionisation Anomaly (EIA) crest. In general strong dependency of Sq(H) field on solar cycle has been observed. First peak of SC24 was visible in Sq(H) field at both observatories. However, at HON maximum Sq(H) was observed in 2015 instead of 2014, a year later than the year of solar maximum. Prominent longitudinal difference has been noted between both observatories. At HON, maximum Sq(H) was observed during equinox while at SON it was noted during equinox and summer as a consequence of shift in latitude of Sq focus. Phase shift of Sq(H) at SON followed a general trend, that is maximum Sq(H) shifted to later hours in solar maximum as compared to solar minimum. Whereas, an opposite trend was noted at HON which might be due to coastal effect. In case of seasonal phase shift, at both observatories maximum Sq(H) occurred at later hours in summer than in winter which is opposite to the results obtained by many workers. These points need further investigation and geomagnetic as well as wind, and electric field data of other observatories situated at the EIA crest region is required to interpret the Sq(H) phase shift extensively.     

Current barriers and factors of success in the diffusion of satellite services in Europe

Satellite services benefit civil society by helping tackle challenges such as climate change, the digital divide, etc. They have the potential to deliver concrete benefits to European society through innovative services supporting economic, societal and environmental policies. Such benefits can trigger increased public support for space in Europe. However, this potential has yet to be achieved. This paper argues that technological bias, the diversity of interests and initiatives among stakeholders and their individual actions do not always serve their collective objective to ensure wide diffusion of satellite services. It draws on theories of diffusion of innovation and on its authors' participatory work with the space and the user communities and at their interface in an effort to help diffuse satellite services within civil society. One of the major causes of insufficient service diffusion is the weakness of the interface between the space and user communities; some of factors that currently contribute to this state of affairs are the space community's over-reliance on publicly financed, technical demonstration projects as solutions to service diffusion; insufficient coordination by public authorities of innovation policies and programmes with other public policies and objectives; and an insufficient integration of satellite services within users' culture, traditional tools and services. The discussion allows for conclusions to be drawn on how the system of stakeholders could function better in order for satellite services to be successfully diffused in Europe.     

Resistance of bacterial endospores to outer space for planetary protection purposes--experiment PROTECT of the EXPOSE-E mission

Spore-forming bacteria are of particular concern in the context of planetary protection because their tough endospores may withstand certain sterilization procedures as well as the harsh environments of outer space or planetary surfaces. To test their hardiness on a hypothetical mission to Mars, spores of Bacillus subtilis 168 and Bacillus pumilus SAFR-032 were exposed for 1.5 years to selected parameters of space in the experiment PROTECT during the EXPOSE-E mission on board the International Space Station. Mounted as dry layers on spacecraft-qualified aluminum coupons, the "trip to Mars" spores experienced space vacuum, cosmic and extraterrestrial solar radiation, and temperature fluctuations, whereas the "stay on Mars" spores were subjected to a simulated martian environment that included atmospheric pressure and composition, and UV and cosmic radiation. The survival of spores from both assays was determined after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110?nm) as well as the martian UV spectrum (λ≥200?nm) was the most deleterious factor applied; in some samples only a few survivors were recovered from spores exposed in monolayers. Spores in multilayers survived better by several orders of magnitude. All other environmental parameters encountered by the "trip to Mars" or "stay on Mars" spores did little harm to the spores, which showed about 50% survival or more. The data demonstrate the high chance of survival of spores on a Mars mission, if protected against solar irradiation. These results will have implications for planetary protection considerations.     

A high-order SPH method by introducing inverse kernels

The smoothed particle hydrodynamics (SPH) method is usually expected to be an effi-cient numerical tool for calculating the fluid-structure interactions in compressors; however, an endogenetic restriction is the problem of low-order consistency. A high-order SPH method by intro-ducing inverse kernels, which is quite easy to be implemented but efficient, is proposed for solving this restriction. The basic inverse method and the special treatment near boundary are introduced with also the discussion of the combination of the Least-Square (LS) and Moving-Least-Square (MLS) methods. Then detailed analysis in spectral space is presented for people to better under-stand this method. Finally we show three test examples to verify the method behavior.     

Detection of Envisat RA2/ICE-1 retracked radar altimetry bias over the Amazon basin rivers using GPS

Altimetry is now routinely used to monitor stage variations over rivers, including in the Amazon basin. It is desirable for hydrologic studies to be able to combine altimetry from different satellite missions with other hydrogeodesy datasets such as leveled gauges and watershed topography. One requirement is to accurately determine altimetry bias, which could be different for river studies from the altimetry calibrated for deep ocean or lake applications. In this study, we estimate the bias in the Envisat ranges derived from the ICE-1 waveform retracking, which are nowadays widely used in hydrologic applications. As a reference, we use an extensive dataset of altitudes of gauge zeros measured by GPS collocated at the gauges. The thirty-nine gauges are spread along the major tributaries of the Amazon basin. The methodology consists in jointly modeling the vertical bias and spatial and temporal slope variations between altimetry series located upstream and downstream of each gauge. The resulting bias of the Envisat ICE-1 retracked altimetry over rivers is 1.044 ± 0.212 m, revealing a significant departure from other Envisat calibrations or from the Jason-2 ICE-1 calibration.