SENSOR: a tool for the simulation of hyperspectral remote sensing systems

The consistent end-to-end simulation of airborne and spaceborne earth remote sensing systems is an important task, and sometimes the only way for the adaptation and optimisation of a sensor and its observation conditions, the choice and test of algorithms for data processing, error estimation and the evaluation of the capabilities of the whole sensor system.The presented software simulator SENSOR (Software Environment for the Simulation of Optical Remote sensing systems) includes a full model of the sensor hardware, the observed scene, and the atmosphere in between. The simulator consists of three parts. The first part describes the geometrical relations between scene, sun, and the remote sensing system using a ray-tracing algorithm. The second part of the simulation environment considers the radiometry. It calculates the at-sensor radiance using a pre-calculated multidimensional lookup-table taking the atmospheric influence on the radiation into account. The third part consists of an optical and an electronic sensor model for the generation of digital images. Using SENSOR for an optimisation requires the additional application of task-specific data processing algorithms.The principle of the end-to-end-simulation approach is explained, all relevant concepts of SENSOR are discussed, and first examples of its use are given. The verification of SENSOR is demonstrated. This work is closely related to the Airborne PRISM Experiment (APEX), an airborne imaging spectrometer funded by the European Space Agency.     

On a scalar fixed altimetry—gravimetry boundary value problem

For some years existence and uniqueness of the solution of a mixed altimetry — gravimetry boundary value problem is under investigation. Usually the size and the shape of the continental part of the Earth's surface is considered as unknown. This leads to a partly free and partly fixed mixed boundary value problem. A solution exists if the area of the continental part is sufficiently small. Obviously, this condition is not fulfilled in reality. Because the GPS is now fully operational, nowadays the size and the shape of the continental part of the Earth's surface can be considered as known, too. The aim of this article is to study the resulting fixed mixed boundary value problem and to prove the existence and uniqueness of its solution for an arbitrary distribution of land and sea at the Earth's surface.     

Latitudinal changes in siphonophore assemblages across the Atlantic sector of the Southern Ocean

Siphonophores are commonly considered to be useful indicators of water masses and water-mass movement, but their employment as such across the wider Southern Ocean has not so far been attempted. We redress this here using archived samples, collected during January–February 1993 along a transect from Cape Town to the South African National Antarctic Expedition (SANAE) base in Antarctica, and compare the patterns generated with those determined from a prior analysis of whole assemblages at lower taxonomic resolution. Twenty-one species were identified from 18 of the original 53 samples collected, and two distinct assemblages were confirmed as separated by the Sub-Antarctic Front. That to the south was characterised by low diversity and high abundance and was dominated by cold-water specialists, whereas that to the north comprised a larger number of subtropical and temperate species at low abundance. Assemblage structure was strongly influenced by the mixed layer depth, sea surface salinity and chlorophyll a concentration, as well as mesozooplankton biomass. Congruence with the whole-assemblage study was high, indicating that this taxon can be suitably employed as a proxy in studies such as this. The study emphasises the value of archived plankton samples and makes a plea for better curation.     

Suspended sediment advection by tidal currents off the Huanghe (Yellow River) delta

Studies to date indirectly indicate that only a small percentage of the sediment discharged by the Huanghe (Yellow River) is presently transported from the Gulf of Bohai to the Huanghai (Yellow Sea). Direct measurements in early summer 1985 show low concentrations of suspended sediment east of 119°45E but high concentrations in Bohai Bay. Stokes drift associated with an amphidrome of the M₂ tide may contribute to a northwestward transport of Huanghe sediment.     

Sediment thixotropy and submarine mass movement,Huanghe Delta,China

Laboratory analysis of clayey silt from the offshore Huanghe Delta reveals thixotropic behavior. Fall cone tests show strength loss on remolding followed by strength regain at virtually constant water contents. The delta-front sediments experience wave loading during storms and widespread mass movement has been detected by acoustic surveying. Measurements from sea floor instruments and repeated sonographic survey during storms indicate repeated episodes of sediment motion consistent with thixotropy.     

The phoshate mineral associations of the Tsaobismund pegmatite,Namibia

A detailed mineralogical investigation using the classical methods of identification by X-ray diffraction and by optical properties in thin sections, has revealed thirty one phosphate minerals occurring in the Tsaobismund pegmatite. This investigation is complemented by wet chemical and, mainly, electron microprobe analyses performed on the phosphates known to be typomorphic or considered to be relevant to the hydrothermal alteration. Additionally, microprobe analyses are also given for garnet, gahnite, and ferrocolumbite associated with the phosphates. On the basis of their chemical composition, particularly in terms of their Fe, Mn, and Mg contents, three types of triphylites are distinguished. Triphylite 1 only occurs as a primary phase, triphylite 2 shows exsolution lamellae of sarcopside, and triphylite 3 is partly replaced by a fluorophosphate of the triplite-zwieselite series. These minerals constitute three generations of the parent phases, which were progressively transformed by metasomatic processes, hydrothermal alteration, and by weathering, to give finally three types of complex associations. The Li(Fe,Mn)PO₄ minerals appear to be more sensitive to such transformations than those of the (Fe,Mn)₂PO₄F series. Four main stages of hydrothermal alteration processes have been recognized in the Tsaobismund pegmatite: (i) the Mason-Quensel sequence results from a progressive oxidation of Fe and Mn, and a concomitant Li-leaching of triphylite yielding ferrisicklerite and heterosite, successively; (ii) the metasomatic exchange of Na for Li produces alluaudite; in the present case, the formation of hagendorfite from triphylite 2 is considered to be earlier than the generation of alluaudite-Na occurring in the three associations; (iii) the hydration phase mainly transforms the parent Li(Fe,Mn)PO₄ phase into grey hureaulite, associated with barbosalite and tavorite; (iv) the formation of fluorapatite, not particularly widespread, replaces alluaudite-Na, as well as zwieselite s.l. The following crystallization sequence of the initially formed phosphate minerals is proposed: triphylite 1 triphylite 2 + sarcopside (associated with garnet) triphylite 3 + zwieselite s.l. The most prominent feature of this succession is the increase in the Mg and Zn contents in the composition of the phosphates, as well as the decrease in their Li contents. The variations of the Fe/Mn ratios in this sequence are discussed. The succession triphylite-zwieselite within weakly differentiated and Li-poor pegmatites is of general significance.     

Fault Controlled Hydrogeology at a Waste Pile

Geologic mapping, subsurface drilling and monitoring well data indicate the existence of a complex and irregular ground water regime in the vicinity of a cement kiln dust pile on an inactive splay of the Garlock Fault System. Artesian flow, active seeps and water levels that are substantially higher than the elevation of apparent saturated conditions encountered during drilling show that ground water flows upward in certain localized zones. Tracing of chemical indicator parameters characteristic of kiln dust leachate shows that the dust pile is not affecting the chemistry of nearby ground water.     

Quaternary maar volcanism near karapinar in central Anatolia

In Central Anatolia, Quaternary olivine basalts overlie the Neogene calcalkaline and sialic post-orogenic volcanic series. Crater forms, cones and lava fields generally exhibit a very fresh morphology suggesting a sub-recent age. Near the town of Karapinar, eruptions took place through the shallow waters of a lake which occupied the present Konya-Eregli plain during Quaternary times. Depending on the varying influence of phreatomagmatic effects, hyaloclastitic tuff rings and maar craters, both rich in sideromelane and its palagonitic alteration products, or subaerial red cinder cones developed. The maar phase is characterized by a large development of base surge structures. The basalts are alkaline and, mostly, Ne-normative and are distinct for their low TiO₂ content and low Fe/Mg ratio from the alkali olivine basalts from oceanic and stable continental areas.