Dynamical attitude model for Gaia

The Dynamical Attitude Model (DAM) is a simulation package developed to achieve a detailed understanding of the Gaia spacecraft attitude. It takes into account external physical effects and considers internal hardware components controlling the satellite. The main goal of the Gaia mission is to obtain extremely accurate astrometry, and this necessitates a good knowledge of Gaia’s behaviour as a spinning rigid body under the influence of various perturbations. This paper describes these perturbations and how they are modelled in DAM.     

The Upper Middle Rhine Valley as a risk area

The Upper Middle Rhine Valley, granted the status of a World Heritage site, is well known for its unique inner narrow valley of Quaternary age with its historical legacy of numerous medieval castles and old towns. Less known is that this has always been a risk area of floods and gravitative mass movements. Up to the recent past, mainly ice floods caused enormous damage. The inhabitants of the valley were well aware that they lived in a risk area, but they had learned to handle the flood hazard. With the demise of ice floods over the last 40 years, due to climate change and because of the additional heating of the river water by power plants, the awareness of flood hazards has been much diminished, in contrast to that of potential damage by rockfalls and landslides which were also much feared in the past, though at the local level only. Still in the people’s memory is the Kaub catastrophe of March 10, 1876, when 28 persons were killed by a landslide. Nowadays, even minor rockfalls are a major threat, as they will affect the much-used traffic lines on both banks of the river, in particular the railroads. Therefore, since 2002, on behalf of German Rail (Deutsche Bahn, DB), all problematic slopes have been protected by costly steel-ring nets, although they are an aesthetic problem by UNESCO standards. The feeling of absolute safety created among the public is only subjective, though, as planners are well aware of. Moreover, the impact of modern climate change on slope stability is nearly unknown. Therefore, it is still necessary to develop a risk map for the narrow valley, with emphasis on gravitational hazards.     

Observation of Precipitating Systems over Complex Orography with Meteorological Doppler Radars: A Feasibility Study

Summary  This paper concerns the use of airborne or ground-based Doppler radars to observe precipitating systems over complex orography. As nearly all of the previous experiments involving Doppler radars were conducted over flat surfaces over the continents or the oceans, new techniques are needed firstly to separate ground clutter from meteorological signal and, in the case of airborne Doppler observations, to deduce navigational errors. Secondly, it is necessary to take the atmospheric circulation induced by orography into account in the three-dimensional wind field analysis. Variational techniques are presented to solve these problems. The proposed methods are tested with simulated ground-based and airborne Doppler radar observations for analytic flows over analytic terrains and for numerically simulated wind and reflectivity fields for the Brig event (22 September 1993) of heavy precipitation over the southern flank of the Alps (Cosma and Richard, 1998), and with actual airborne Doppler data relative to weak snow showers over the Rocky Mountains on 12 March 1995. Received March 22, 1999/Revised June 1, 1999     

A Long-Term Decrease of the Mid-Size Segmentation Lengths Observed in the He <Emphasis Type="SmallCaps">ii</Emphasis> (30.4 nm) Solar EUV Emission

Power spectra of segmentation-cell length (a dominant length scale of EUV emission in the transition region) from full-disk He?ii extreme ultraviolet (EUV) images observed by the Extreme ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO) and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) during periods of quiet-Sun conditions for a time interval from 1996 to 2015 were analyzed. The spatial power as a function of the spatial frequency from about 0.04 to 0.27 (EIT) or up to 0.48 (AIA) Mm^?1 depends on the distribution of the observed segmentation-cell dimensions – a structure of the solar EUV network. The temporal variations of the spatial power reported by Didkovsky and Gurman (Solar Phys. 289, 153, 2014) were suggested as decreases at the mid-spatial frequencies for the compared spectra when the power curves at the highest spatial frequencies of 0.5 pix^?1 were adjusted to match each other. This approach has been extended in this work to compare spectral ratios at high spatial frequencies expressed in the solar spatial frequency units of Mm^?1. A model of EIT and AIA spatial responses allowed us to directly compare spatial spectral ratios at high spatial frequencies for five years of joint operation of EIT and AIA, from 2010 to 2015. Based on this approach, we represent these ratio changes as a long-term network transformation that may be interpreted as a continuous dissipation of mid-size network structures to the smaller-size structures in the transition region. In contrast to expected cycling of the segmentation-cell dimension structures and associated spatial power in the spectra with the solar cycle, the spectra demonstrate a significant and steady change of the EUV network. The temporal trend across these structural spectra is not critically sensitive to any long-term instrumental changes, e.g. degradation of sensitivity, but to the change of the segmentation-cell dimensions of the EUV network structure.     

Photoelectric device for monitoring the movement of a torsion balance beam

Manufactured and tested in his work is a photoelectric device that makes it possible to automatically determine the relative angular position of the beam of a miniature torsion balance, angular readings being discretized with various time step values and stored in a computer. Measurements were taken with this device that captured the occurrence of the partial solar eclipse on September 11, 2007, and confirmed the fact, established previously through visual observation, that the position of torsion balance beams changed at the instant an eclipse took place.     

Climatic and geographic factors affect ecosystem multifunctionality through biodiversity in the Tibetan alpine grasslands

Ecosystem multifunctionality(EMF), the simultaneous provision of multiple ecosystem functions, is often affected by biodiversity and environmental factors. We know little about how the interactions between biodiversity and environmental factors affect EMF. In this case study, a structural equation model was used to clarify climatic and geographic pathways that affect EMF by varying biodiversity in the Tibetan alpine grasslands. In addition to services related to carbon, nitrogen, and water cycling, forage supply, which is related to plantproductivity and palatability, was included in the EMF index. The results showed that 72% of the variation in EMF could be explained by biodiversity and other environmental factors. The ratio of palatable richness to all species richness explained 8.3% of the EMF variation. We found that air temperature, elevation, and latitude all affected EMF, but in different ways. Air temperature and elevation impacted the aboveground parts of the ecosystem, which included plant height, aboveground biomass, richness of palatable species, and ratio of palatable richness to all species richness. Latitude affected EMF by varying both aboveground and belowground parts of the ecosystem, which included palatable speciesrichness and belowground biomass. Our results indicated that there are still uncertainties in the biodiversity–EMF relationships related to the variable components of EMF, and climatic and geographic factors. Clarification of pathways that affect EMF using structural equation modeling techniques could elucidate the mechanisms by which environmental changes affect EMF.     

Regularized derivatives of potential fields and their role in semi-automated interpretation methods

Evaluation of higher derivatives (gradients) of potential fields plays an important role in geophysical interpretation (qualitative and/or quantitative), as has been demonstrated in many approaches and methods. On the other hand, numerical evaluation of higher derivatives is an unstable process – it has the tendency to enlarge the noise content in the original data (to degrade the signal-to-noise ratio). One way to stabilize higher derivative evaluation is the utilization of the Tikhonov regularization. In the submitted contribution we present the derivation of the regularized derivative filter in the Fourier domain as a minimization task by means of using the classical calculus of variations. A very important part of the presented approach is the selection of the optimum regularization parameter – we are using the analysis of the C-norm function (constructed from the difference between two adjacent solutions, obtained for different values of regularization parameter). We show the influence of regularized derivatives on the properties of the classical 3D Euler deconvolution algorithm and apply it to high-sensitivity magnetometry data obtained from an unexploded ordnance detection survey. The solution obtained with regularized derivatives gives better focused depth-estimates, which are closer to the real position of sources (verified by excavation of unexploded projectiles).     

Synchrotron spectra of short-period pulsars

A model with synchrotron radiation near the light cylinder is proposed to explain the observed spectra of short-period pulsars (P≤0.1 s). These spectra can be described if a power-law energy distribution of the emitting electrons with exponent γ=2–8 is assumed. For most pulsars, the peak frequency ν_m is below 10 MHz. The ν_m(γ) dependence is derived, and shows that the peak frequencies for pulsars with spectral indices α<1.5 may fall in the observable range. In particular, ν_m may be ν_m ～ 100 MHz for PSR J0751 + 1807 and PSR J1640 + 2224. The observed radio spectrum of Geminga (PSR J0633 + 1746) can be described by a synchrotron model with a monoenergetic or Maxwellian distribution of relativistic electrons and a small angle β between the spin axis and magnetic moment (β ～ 10°).     

Observation of the solar eclipse 1966 May 20 in the region between 3.2 cm to 2.7 m wavelength

The solar eclipse 1966 May 20 was observed at 3.2, 10, 15, 20, 54, 59 cm, 1.05, 1.34 and 2.7 m wavelength by the observatories of the Heinrich-Hertz-Institut. The meter-wavelength observations were superposed by a noise storm. The result shows a region of enhanced radiation from the plages near the central meridian at the short wavelengths. Consulting additionally the observations made at Kiel, NERA, and Ondejov in the region of about 1.2 m wavelength it is possible to localize the source of the noise storm.