ALBERT

Description: Remotely sensed data are affected by system (sensor and platform), and scene related effects. For quantitative investigations the spectral, radiometric characteristics of the system and scene have to be known. The relevant effects and their possible influence on an image have to be specifically determined for every remote sensing system and adequate description parameters need to be updated and reported on a regular basis as they are carried out, e.g., for the AVIRIS system. It is evident that the strength of the influence of similar effects in very dependent on the accessibility of auxiliary information about such sensor systems. Degradation in a spaceborne system can normally be just reported and cannot be corrected. In contrast, an airborne sensor can be evaluated, maintained and improved periodically. Such maintenance efforts are particularly important because airborne systems are exposed to extreme and changing environments. These include tens of takeoffs and landing each year as well as extreme changes in temperature and humidity on the tarmac and in flight. For the AVIRIS system there are environmental stresses such as changes in temperature, air pressure, humidity, vibration of the platform or scene-related reasons like atmospheric conditions, and topography. The information contained in the auxiliary files included with the AVIRIS data can be used to assess these effects and compensate for them. In addition the spectral, radiometer and geometric calibration data contained in the auxiliary file are required for quantitative analysis of the data. The paper describes tools to access the auxiliary information that characterizes the AVIRIS system. These tools allow the examination of parameters that may impact the quality of the measured AVIRIS image. An example of the use of this auxiliary data was carried out with regard to a parametric geocoding approach. Emphasis is placed on the reported auxiliary information that describes the geometric character of the AVIRIS data in 1991. Results are presented using data from the AVIRIS flight #910705, run 6 and 7 of the NASA MAC Europe 1991 campaign in a test site in Central Switzerland.

Description: Remotely sensed data have geometric characteristics and representation which depend on the type of the acquisition system used. To correlate such data over large regions with other real world representation tools like conventional maps or Geographic Information System (GIS) for verification purposes, or for further treatment within different data sets, a coregistration has to be performed. In addition to the geometric characteristics of the sensor there are two other dominating factors which affect the geometry: the stability of the platform and the topography. There are two basic approaches for a geometric correction on a pixel-by-pixel basis: (1) A parametric approach using the location of the airplane and inertial navigation system data to simulate the observation geometry; and (2) a non-parametric approach using tie points or ground control points. It is well known that the non-parametric approach is not reliable enough for the unstable flight conditions of airborne systems, and is not satisfying in areas with significant topography, e.g. mountains and hills. The present work describes a parametric preprocessing procedure which corrects effects of flight line and attitude variation as well as topographic influences and is described in more detail by Meyer.

Description: ODP Legs 106 and 109 drilled zero-age crust at Site 648 on the axis of the Mid-Atlantic Ridge and recovered sparsely to moderately phyric but chemically homogeneous basalt. Plagioclase phenocrysts in Site 648 basalts exhibit a variety of zoning patterns and compositions including: (1) tabular (An84) cores mantled by more sodic zones (An80 and An75), (2) tabular (An80) cores mantled by narrow (An84 and An75) zones, (3) skeletal cores (An80-78) enclosing sodic (An75) patches, and (4) rounded cores (An75) surrounded by skeletal (An80-78) mantles. Backscattered electron images have been used to define zone morphologies in 28 crystals; major element compositions of the zones have been determined by electron microprobe; and Mg, K, Ti, Fe, and Sr concentrations have been determined by ion microprobe. Equilibrium partitioning of minor and trace elements between crystals and liquids occurred during stable growth of tabular cores and inner rims. Disequilibrium partitioning occurred during rapid growth of crystal rims, resulting in enrichment of incompatible trace and minor elements, and during growth of calcic zones with skeletal and acicular morphology, resulting in enrichment of Fe and Sr and depletion of Mg, K, and Ti. Crystal/liquid partition coefficients estimated from the composition of inner rims and glass are DMg = 0.03, DK = 0.15, DTi = 0.028, DFe = 0.05, and DSr = 1.82. Using these partition coefficients, we have calculated the composition of primitive liquid in equilibrium with phenocryst cores. The estimated liquid composition is similar to primitive basalt compositions from the Kane Fracture Zone except for a much higher Ca/(Ca + Na) ratio which resembles values for MAR plume basalts. The diversity in plagioclase morphologies and compositions is explained by mixing of melts at different stages of evolution and stored in separated but interconnected reservoirs, as previously suggested by Kuo and Kirkpatrick (1982, doi:10.1007/BF00376957).