The design of the Central-Axis Reflector (ZAS)

The Central-Axis Reflector, the design principle which is presented below is a segmented-mirror telescope. The inventions relate mainly to the optical system and to the tracking apparatus.A large number of small individual mirror bodies, ground off-axis (hexagonal/polygonal) produce one primary mirror with closed circular aperture when joined together.The overall design of the tracking apperatus results directly —and thus without unnecessary adornment — from the two planes of to aminimum but which are required for tracking of the telescope.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.     

Über den Einfluß von Meeresspiegelschwankungen auf Flachwassersedimente im Schwäbischen Jura

Zusammenfassung Im Ablagerungsbecken des Unteren Lias und Dogger dürften, wenn nicht Ebbe und Flut, so doch aperiodische Schwankungen des Meeresspiegels um mehrer Meter aufgetreten sein. Durch die Spiegelschwankungen wird das Sedimentgefüge in von Ort zu Ort wechselndem Ausmaß geändert, austretendes Porenwasser trägt außerdem zur Sedimentbildung bei.

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Summary Aperiodic fluctuations of sea level, caused by wind, during some periods of Lower and Middle Jurassic in Southern Germany should have had similar effects as tides in Watten today, altering the fabric of sediments and bringing pore water low in pH and eH to the surface. Glauconite and Chamosite may have been formed by mixing of normal sea water with pore water.

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Mit 1 Textabbildung

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Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet.     

Escape models of the Alpine-Carpathian-Pannonian region in the light of palaeomagnetic observations

Recent tectonic models of the Alpine-Carpatho-Pannonian region (ALCAPA) assume a large eastward shift of the Transdanubian Range domain, in the Cenozoic. Since palaeomagnetism is one of the most powerful tools in solving geodynamic processes, the authors present an approach to the escape problem by using all available and relevant palaeomagnetic data. This data set demonstrates consistency with models put forward by geologists for Jurassic and older ages. From the mid-Jurassic on the Northern Calcareous Alps (NCA) did not share the rotations of the Transdanubian Range domain and of the Southern Alps. After individual movements from Neocomian to Miocene, the Transdanubian Range domain must have drifted northward in the mid-Miocene up to the Southern margin of the Northern Calcareous Alps, before starting the escape in the geologists' definition.     

Potential of Satellite Remote Sensing and GIS for Landslide Hazard Assessment in Southern Kyrgyzstan (Central Asia)

Big landslides are one of the main natural hazards in Kyrgyzstan, which are concentrated in the foothills of the high mountain ranges along the Eastern rim of the Fergana Basin. Because of the high number of landslides and their occurrence over large areas there is a strong need for effective and objective landslide hazard assessment at a regional scale. In Kyrgyzstan satellite remote sensing data represent the only source of multitemporal information about surface conditions covering large areas. Against this background the goal is the development of a satellite remote sensing and GIS-based system for quantitatively oriented and spatially differentiated hazard assessment. During the presented pilot investigations in the area of the Upper Maili Suu river basin a methodological framework has been developed incorporating remote sensing and GIS techniques for various levels of information extraction. So far, methodological investigations have been focused on the potential of satellite remote sensing data from different optical (Landsat-(E)TM, ASTER, MOMS-2P) and radar (ERS-1/2) systems for the creation of an improved knowledge basis for hazard assessment. This includes landslide identification, generation of topographic information and characterization of the geological setting. The derived primary information have been analyzed in a GIS environment to gain an improved process understanding as a main prerequisite for successful hazard assessment. The results show that currently available satellite remote sensing data are suitable for landslide investigation in Kyrgyzstan. Full exploitation of their information potential requires combined analysis with other thematic information based on methods of interactive and automated information extraction.     

A review of pollutants in the sea-surface microlayer (SML): a unique habitat for marine organisms

Boundary layers between different environmental compartments represent critical interfaces for biological, chemical and physical processes. The sea-surface microlayer (uppermost 1-1000 microm layer) forms the boundary layer interface between the atmosphere and ocean. Environmental processes are controlled by the SML, and it is known to play a key role in the global distribution of anthropogenic pollutants. Due to its unique chemical composition, the upper organic film of the SML represents both a sink and a source for a range of pollutants including chlorinated hydrocarbons, organotin compounds, petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAH) and heavy metals. These pollutants can be enriched in the SML by up to 500 times relative to concentrations occurring in the underlying bulk water column. The SML is also a unique ecosystem, serving as an important habitat for fish eggs and larvae. Concentration ranges and enrichment factors of pollutants in the SML in different areas of the world's oceans have been critically reviewed, together with available toxicity data for marine biota found within the SML. Overall, the SML is highly contaminated in many urban and industrialized areas of the world, resulting in severe ecotoxicological impacts. Such impacts may lead to drastic effects on the marine food web and to fishery recruitment in coastal waters. Studies of the toxicity of fish eggs and larvae exposed to the SML contaminants have shown that the SML in polluted areas leads to significantly higher rates of mortality and abnormality of fish embryos and larvae.     

Accessibility for High Asia： Comparative Perspectives on Northern Pakistan＇s Traffic Infrastructure and Linkages with Its Neighbours in the Hindukush-Karakoram- Himalaya

Starting with a discussion of development concepts which were applied in practice and which followed the developmentalist paradigm the expansion of traffic infrastructure in colonial and post-colonial periods is presented for the High Asian mountain rim. Selective railways and roads are the major feature of this development, which aimed first on serving the convenience of hill station visitors and followed strategic considerations later on. This bias between regional planning and implementation remains a characteristic feature. At the same time traffic infrastructure without asphalt roads is important for the mountain areas, thus breaking up the strong correlation between development and asphalt roads.     

Characterization of Compass M-1 signals

An analysis of observations from China’s first medium earth orbit satellite Compass M-1 is presented, with main focus on the first orbit and clock solution for this satellite. The orbit is computed from laser ranging measurements. Based on this orbit solution, the apparent clock offset is estimated using measurements from two GNSS receivers, which allow Compass tracking. The analysis of the clock solutions reveals unexpectedly high dynamics in the pseudorange and carrier-phase observations. Furthermore, carrier-to-noise density ratio, pseudorange noise, and multipath are analyzed and compared to GPS and GIOVE. The results of the clock analysis motivate further research on the signals of the geostationary satellites of the Compass constellation.     

Critical distances: Comparing measures of spatial accessibility in the riverine landscapes of Peruvian Amazonia

Quantitative measures of accessibility are increasingly used in land cover change modeling and in assessing human pressure on the environment. In riverine Amazonia the significance of physical accessibility for biodiversity, land use patterns and economic livelihoods is widely acknowledged, but attempts to quantify accessibility in practice have been few in number. In this study we compare different distance- and frequency-based measures of spatial accessibility and develop a quantitative model of accessibility patterns for the north-eastern Peruvian Amazonia where rivers form the core of the transportation network. We model accessibility between the rural areas of the Loreto region and the capital city of Iquitos, using different distance algorithms in a geographic information system, and complement the distance model with information on river boat frequencies and transport capacities. Patterns of accessibility are visualized in terms of potential production zones for different types of agricultural and non-timber forest products.This study demonstrates how results from different accessibility measures vary considerably. The mean Euclidean distance to Iquitos is almost 270 km, the mean network distance nearly 760 km and the mean travel time 70 h. Observed network distances from validation points to Iquitos are on average 1.6 times longer than Euclidean distances, and for the whole study area, the average ratio between modeled network distances and Euclidean distances is 3.1. The correlation between network distances and time distances is very strong, but time distances are relatively shorter along the major channels where boat traffic is considerably faster than along narrow, tightly meandering rivers. Measures of boat frequency and transport capacity show that availability of transport possibilities is highly varying across the region. These measures provide insights into the ’thickness’ of trade, indicating the level of market integration for riverine settlements. We conclude that quantifying accessibility in an environment like Peruvian Amazonia requires measures that take into account the spatial structure and dynamic nature of the riverine transportation network. Time as a unit of distance provides the most relevant measure of accessibility in the Amazonian context, where many human actions and traditional livelihoods are controlled by travel times between the regional core and the hinterland.     

Reliable estimation of orbit errors in spaceborne SAR interferometry

An approach to improve orbital state vectors by orbit error estimates derived from residual phase patterns in synthetic aperture radar interferograms is presented. For individual interferograms, an error representation by two parameters is motivated: the baseline error in cross-range and the rate of change of the baseline error in range. For their estimation, two alternatives are proposed: a least squares approach that requires prior unwrapping and a less reliable gridsearch method handling the wrapped phase. In both cases, reliability is enhanced by mutual control of error estimates in an overdetermined network of linearly dependent interferometric combinations of images. Thus, systematic biases, e.g., due to unwrapping errors, can be detected and iteratively eliminated. Regularising the solution by a minimum-norm condition results in quasi-absolute orbit errors that refer to particular images. For the 31 images of a sample ENVISAT dataset, orbit corrections with a mutual consistency on the millimetre level have been inferred from 163 interferograms. The method itself qualifies by reliability and rigorous geometric modelling of the orbital error signal but does not consider interfering large scale deformation effects. However, a separation may be feasible in a combined processing with persistent scatterer approaches or by temporal filtering of the estimates.