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.     

Review of Pi2 Models

More than half a century after the discovery of Pi2 pulsations, Pi2 research is still vigorous and evolving. Especially in the last decade, new results have provided supporting evidence for some Pi2 models, challenged earlier interpretations, and led to entirely new models. We have gone beyond the inner magnetosphere and have explored the outer magnetosphere, where Pi2 pulsations have been observed in unexpected places. The new Pi2 models cover virtually all magnetotail regions and their coupling, from the reconnection site via the lobes and plasma sheet to the ionosphere. In addition to understanding the Pi2 phenomenon in itself, it has also been important to study Pi2 pulsations in their role as transient manifestations of the coupling between the magnetosphere and the ionosphere. The transient Pi2 is an integral part of the substorm phenomenon, especially during substorm onset. Key questions about the workings of magnetospheric substorms are still awaiting answers, and research on Pi2 pulsations can help with those answers. Furthermore, the role of Pi2 pulsations in association with other dynamic magnetospheric modes has been explored in the last decade. Thus, the application of Pi2 research has expanded over the years, assuring that Pi2 research will remain active in this decade and beyond. Here we review recent advances, which have given us a new understanding of Pi2 pulsations generated at various places in the magnetosphere during different magnetospheric modes. We review seven Pi2 models found in the literature and show how they are supported by observations from spacecraft and ground observatories as well as numerical simulations. The models have different degrees of maturity; while some enjoy wide acceptance, others are still speculative.     

Design-to-Cost Applied Within an Integrated System Model

In an environment of declining financial budgets for space projects, new approaches - such as Design-To-Cost - are being implemented to improve today's satellite design processes. Using an example of a current mission (the power subsystem of the Solar Probe spacecraft) under study at NASA's Jet Propulsion Laboratory, the main part of the paper discusses an Integrated System Model (structured into a performance model, a cost model, and an effectiveness model) that is part of a model-based design process used to perform cost-effectiveness trades. A simulation tool is used during the first step to size the components of the power subsystem, and then simulate its performance during operation. The determined dimensions are transferred into an EXCEL^TM-spreadsheet and linked to the components' costs. With a cost accounting tool that combines cost estimating relationships with the Work Breakdown Structure of the power subsystem, the life-cycle cost of each alternative design concept is computed. To determine the cost-risk of the different design alternatives for each component, cost probability distributions are introduced. By performing Monte-Carlo simulations, cost sensitivities are revealed. In the next step of the trade study process, the effectiveness of the alternatives is analyzed. Having determined cost and effectiveness, estimates can be made for where the different alternatives lie in the design space. The last part of the paper identifies the main drivers for the spacecraft's performance and cost. Finally it is shown how the mission design benefited from the Integrated System Model and from the application of Design-To-Cost.     

Obscured Activity: AGN, Quasars, Starbursts and ULIGs Observed by the Infrared Space Observatory

Some of the most ‘active’ galaxies in the Universe are obscured by large quantities of dust and emit a substantial fraction of their bolometric luminosity in the infrared. Observations of these infrared luminous galaxies with the Infrared Space Observatory (ISO) have provided a relatively unabsorbed view to the sources fuelling this active emission. The improved sensitivity, spatial resolution and spectroscopic capability of ISO over its predecessor Infrared Astronomical Satellite (IRAS) of enabled significant advances in the understanding of the infrared properties of active galaxies. ISO surveyed a wide range of active galaxies which, in the context of this review, includes those powered by intense bursts of star formation as well as those containing a dominant active galactic nucleus (AGN). Mid-infrared imaging resolved for the first time the dust enshrouded nuclei in many nearby galaxies, while a new era in infrared spectroscopy was opened by probing a wealth of atomic, ionic and molecular lines as well as broad band features in the mid- and far-infrared. This was particularly useful, since it resulted in the understanding of the power production, excitation and fuelling mechanisms in the nuclei of active galaxies including the intriguing but so far elusive ultraluminous infrared galaxies. Detailed studies of various classes of AGN and quasars greatly improved our understanding of the unification scenario. Far-infrared imaging and photometry revealed the presence of a new very cold dust component in galaxies and furthered our knowledge of the far-infrared properties of faint starbursts, ULIGs and quasars. We summarise almost nine years of key results based on ISO data spanning the full range of luminosity and type of active galaxies.     

X-ray source populations in nearby star-forming galaxies

We present results on the X-ray source populations of nearby star-forming galaxies based on Chandra observations. First we discuss the monitoring campaigns on the Antennae and M82 galaxies. In both cases we find that the majority of the X-ray sources exhibit intensity and/or spectral variability. However, despite of this variability, we do not find any statistically significant variations of their X-ray luminosity functions (XLFs). We also find that the majority of the X-ray sources are associated with star-forming regions, although we do not always identify optical counterparts to the X-ray sources. Especially in the case of M82 we find that the most luminous sources are clustered in the central region of the galaxy. Finally, we present the first results from a study of a sample of nearby star-forming galaxies which form a starburst age sequence: although their XLFs to first order are represented by power-laws with consistent slopes, there is an indication for small variations, suggesting a change of their X-ray binary populations.     

The potential feasibility of chlorinic photosynthesis on exoplanets

The modern search for life-bearing exoplanets emphasizes the potential detection of O(2) and O(3) absorption spectra in exoplanetary atmospheres as ideal signatures of biology. However, oxygenic photosynthesis may not arise ubiquitously in exoplanetary biospheres. Alternative evolutionary paths may yield planetary atmospheres tinted with the waste products of other dominant metabolisms, including potentially exotic biochemistries. This paper defines chlorinic photosynthesis (CPS) as biologically mediated photolytic oxidation of aqueous Cl(-) to form halocarbon or dihalogen products, coupled with CO(2) assimilation. This hypothetical metabolism appears to be feasible energetically, physically, and geochemically, and could potentially develop under conditions that approximate the terrestrial Archean. It is hypothesized that an exoplanetary biosphere in which chlorinic photosynthesis dominates primary production would tend to evolve a strongly oxidizing, halogen-enriched atmosphere over geologic time. It is recommended that astronomical observations of exoplanetary outgoing thermal emission spectra consider signs of halogenated chemical species as likely indicators of the presence of a chlorinic biosphere. Planets that favor the evolution of CPS would probably receive equivalent or greater surface UV flux than is produced by the Sun, which would promote stronger abiotic UV photolysis of aqueous halides than occurred during Earth's Archean era and impose stronger evolutionary selection pressures on endemic life to accommodate and utilize halogenated compounds. Ocean-bearing planets of stars with metallicities equivalent to, or greater than, the Sun should especially favor the evolution of chlorinic biospheres because of the higher relative seawater abundances of Cl, Br, and I such planets would tend to host. Directed searches for chlorinic biospheres should probably focus on G0-G2, F, and A spectral class stars that have bulk metallicities of +0.0 Dex or greater.     

Radiation protective structures on the base of a case study for a manned Mars mission

Plans for interplanetary manned space missions imply significant risks arising from human's exposure to the hostile space environment. Thus the design of reliable protection systems against the ionizing cosmic radiation becomes one of the most relevant issues. In this paper the composition and magnitude of the atmospheric radiation on the planetary surface and for typical interplanetary transfer configurations have been analyzed. The investigation based on prior NASA and ESA mission results, using a manned mission to planet Mars as a case study. According to this, the time-dependent character of the consistency of cosmic radiation has been taken into account, which is justified by the interdependence of the radiation magnitude to the solar cycle. With regard to this paper it implies even solar particle events. The results have been compared to the protective character of different materials potentially usable as a habitat's structural shell and for interplanetary spacecrafts. The investigation aimed on particle energy degradation rates and reduction of secondary particle production. In this regard the physical process of absorbing effectiveness against particle radiation has been examined by analytical calculation and given scientific results, depending on thickness and molecular composition of the materials. The most suitable materials have been used for shield design proposals using different configurations, evaluating the use of aluminium, water tanks and polyethylene bricks.     

Fringe fitting and group delay determination for geodetic VLBI observations of DOR tones

Extracting the group and phase delays of interferometric observations produced in the Very Long Baseline Interferometry (VLBI) measurement concept requires a special fringe fitting and delay search algorithm for the recorded bandwidth. While fringe fitting is in use routinely for several megahertz wide channels in geodetic and astrometric VLBI with quasar observations, fringe fitting for artificial tones of very small bandwidth of artificial signals for Differential One-way Ranging (DOR) requires a different way of handling. In a project called Observing the Chang’E-3 Lander with VLBI (OCEL), the DOR tones emitted by the Chang’E-3 lander were observed in a standard geodetic VLBI mode with 8 or 4?MHz wide channels to maintain compatibility with the corresponding quasar observations. For these observations, we modified the existing fringe fitting program of the Haystack Observatory Processing Software (HOPS), fourfit, to properly handle narrow band DOR tones. The main motivations are that through this modification, the data of quasars and artificial radio sources can be processed in the existing geodetic analysis pipeline, and that the algorithm can be used for similar projects as well. In this paper, we describe the algorithm and show that the new algorithm produces much more reliable group delay results than using the standard fourfit algorithm. This is done by a simulation test and in particular by processing of real observations. It is shown that in many cases, systematic deviations of several nanoseconds, which are seen with the standard fourfit algorithm, can be avoided. The ultimate benefit of the new procedure is demonstrated by reducing the errors in delay triangle closures by at least a factor of 3, which, in the OCEL case, is from ～300 to ～100?ps.     

Self-Adapting dc Converter for Solar Spacecraft Power Supply Selbstanpassender Gleichstromwandler für die Energieversorgung eines Sonnensatelliten

The voltage-current characteristic of solar cells that provide power for a spacecraft can vary over a wide range. For maximum power transfer from the solar cells to the battery system a power converter has to be designed that adjusts its input impedance to a value equal to the output impedance determined by the operating power characteristic of the solar cells. This paper discusses a circuit and calculations for a design to match this condition. The proposed power converter is simple, lightweight, and reliable and will be used in the Sunblazer satellite.