ALBERT

Description: The Transport Collaboration, consisting of researchers from institutions in France, Germany, Italy, and the USA, has established a program to make new measurements of nuclear interaction cross sections for heavy projectiles (Z greater than or equal to 2) in targets of liquid H2, He and heavier materials. Such cross sections directly affect calculations of galactic and solar cosmic ray transport through matter and are needed for accurate radiation hazard assessment. To date, the collaboration has obtained data using the Lawrence Berkeley Laboratory Bevalac HISS facility with 20 projectiles from He-4 to Ni-58 in the energy range 393-910 MeV/nucleon. Preliminary results from the analysis of these data are presented here and compared to other measurements and to cross section prediction formulae.

Description: The two phase sampling technique was applied to estimate the area cultivated with sugar cane in an approximately 984 sq km pilot region of Campos. Correlation between existing aerial photography and LANDSAT data was used. The two phase sampling technique corresponded to 99.6% of the results obtained by aerial photography, taken as ground truth. This estimate has a standard deviation of 225 ha, which constitutes a coefficient of variation of 0.6%.

Description: This paper discusses an exploration of approaches to providing ground data system support by NASA/Goddard Space Flight Center for scientific missions. Two architecture concepts are identified to provide full support using a mission specific instantiation concept, with distributed client-server architecture. The alternatives are assessed for impact to operations, and for hardware and software sizing. Evaluation benefits and risks is also provided.

Description: This paper addresses the aspects of providing mission control to near-earth unmanned scientific missions at the Goddard Space Flight Center (GSFC). Major areas covered include a background of the development of the mission control function, a description of the GSFC ground system elements necessary to provide that mission control, and the developments which are planned to meet the 1980 decade requirements. Particular attention is given to the Payload Operations Control Center and the Command Management function for performing mission control operations.

Description: The objectives of the Consultative Committee for Space Data Systems (CCSDS) include the identification of those common elements of space data systems which, if implemented in a standardized way, will significantly enhance the operation of future cooperative space missions. Recommendations of the CCSDS include packet telemetry and telecommand concepts, coding designs, ancillary data parameters and formats, and data exchange conventions. Consideration is given to the application of CCSDS recommendations.

Description: A ground system is described which is compatible with the operational requirements of the space telescope. The goal of the ground system is to minimize the cost of post launch operations without seriously compromising the quality and total throughput of space telescope science, or jeopardizing the safety of the space telescope in orbit. The resulting system is able to accomplish this goal through optimum use of existing and planned resources and institutional facilities. Cost is also reduced and efficiency in operation increased by drawing on existing experience in interfacing guest astronomers with spacecraft as well as mission control experience obtained in the operation of present astronomical spacecraft.

Description: Submarine slope failures are a well-known geohazard. They are able to destroy seafloor installations along their path and by generating tsunamis they may threaten coastal infrastructures. While the mechanisms involved in submarine landslide generation remain poorly known, there are observations that slope stability can be reduced in the presence of free gas. Here, we present new high-resolution 3D seismic data from the Eivissa Channel between the Iberian Penninsula and the Balearic Promontory in the Western Mediterranean Sea. The data reveal slope stability reduction in this area at least since mid-Quaternary times, and an intimate relationship between fluid migration and slope stability. We show that two landslides, i.e. pre-Ana Slide and Ana Slide, occurred at almost the same location above an erosional channel in the Messinian unconformity. There is seismic evidence that fluids including gas are migrating upwards through this erosional surface and that they charge sedimentary layers at the base of the Ana Slide possibly reducing its strength and predisposing it to failure. Our data show in unprecedented detail the ways in which the presence of gas influences slope stability. The findings illustrate the importance of including high-resolution 3D seismic data in slope stability and tsunami risk assessments to identify shallow gas distribution as one of the main controls on slope stability in gas prone areas.

Description: This work deals with the failure mechanisms of Ana Slide in the Eivissa Channel, in between the Iberian Peninsula and the Balearic Islands, under the effects of gas charging and seismic loading. In situ geotechnical tests and sediment cores obtained at the eastern Balearic slope of the Eivissa Channel suggest that the basal failure surface (BFS) developed as a result of subtle contrasting hydro-mechanical properties at the boundary between a fine-grained unit (U6) overlying a methane-charged relatively coarser unit (U7). Past methane seepage is inferred from seismic reflection profiles and high magnetic susceptibility values in sediments from the slide headwall area. Past methane charging is also supported by further seismic reflection data and isotopic analyses of benthic foraminifera published separately. The possibility of failure for different critical failure surfaces has been investigated by using the SAMU-30 slope stability model software taking into account the role of free methane in the development of the landslide. Failure would occur after SAMU-30 if the undrained shear strength of units U6 and U7 is strongly degraded (i.e. 95%). Wheeler's theory suggests that a 9% free gas saturation would be required to reduce the undrained shear strength by 95%. However, the theory of the undrained equilibrium behaviour of gassy sediments for this methane concentration shows that the excess fluid pressure generated by gas exsolution, estimated at 12% of the effective stress, is not high enough to bring the slope to fail. This led us to consider seismic loading as an additional potential failure mechanism despite the lack of historical data (including instrumental records) on seismicity in the Balearic Islands, therefore assuming that the historical period is not necessarily representative of seismic activity further back in time (i.e. when Ana Slide occurred -61.5 ka ago). Considering current slope conditions, the most critical failure surface obtained by SAMU-30 relates to peak ground accelerations (PGA) of 0.24 g, which relates to magnitude moment Mw = 5 at epicentral distances of 1 km, and 7 :2: Mw :2: 5 at epicentral distances :c; 15 km to Ana Slide. However, no active faults have been identified at so short distance from Ana Slide. Only when shear strength is degraded due to the presence of free methane in units U6 and U7 is considered, the most critical failure surface obtained by SAMU-30 fits with lower magnitude and larger epicentral distances. Consequently, the most plausible hypothesis to explain the occurrence of Ana Slide is the combination of free gas and seismic loading.