M. Livio, S. M. Fall and P. Madau (eds.), The Hubble Deep Field, Space Telescope Conference Series 11

The proceedings of a conference dealing with only one piece of observational activity: the deepest optical image obtained by the HST during a 150 orbit observational program. The main result, presented in several papers, is that we are now able to witness the period of galaxy formation. Very readable too is Allan Sandage's historical review, being the introductory paper to the meeting. This revised version was published online in August 2006 with corrections to the Cover Date.     

Global behavior of the equatorial anomaly since 1999 and effects on GPS signals

Tools to generate VTEC maps were developed. These maps have been used to study the global behavior of the equatorial anomaly since 1999 up to now, and its effects on GPS signal. The VTEC data for any place around the world is based on IONEX data. In this way, a quick annual behavior of the VTEC may be analyzed, and also compared to the VTEC behavior for different places and different years. Based on these data an electron density model taking into account radial as well latitudinal and longitudinal gradients were developed. This model was incorporated in a 3D ray-tracing program. Using this program it was possible to compare the STEC conversion to the VTEC. As expected the results show that the lower the elevation angles of the Satellite Vehicle, the greater the error in the VTEC estimation.     

Monitoring of biologically effective UV irradiance at El Arenosillo (INTA), Andalucia, in Spain.

Biological UV (ultraviolet) dosimetry was applied using the biofilm-technique (DLR patent) to determine the UV levels weighted of biologically weighted UV radiation at the INTA Sounding Station of El Arenosillo at Huelva, Spain (37 degrees 06'N, 6 degrees 44'W, 50 m a s 1=above sea level) on 2 days in 1997 [correction of 1977] (April 1, and May 5). Exposure periods were calculated for clear sky days using a radiative transfer model for erythemal doses to reach 1.3 to 1.5 MED (minimal erythemal dose). Reliability of the radiative transfer model was demonstrated by the doses registered by a Yankee-UV biometer for the same exposure periods as used for the biosensor. This work presents the methodology employed (biofilm-technique utilized [correction of utiliced], calculation of exposing periods with radiative transfer model, etc) and the results obtained with the Yankee biometer and the biofilm. At noon, the ratio of biofilm measurements (Ieff, W/m2=biological effective irradiance, in W/m2) to the UV Biometer data (in MED/h) was 3-4.     

The new international political and strategic context for space policies

For several years there has been substantial growth in the ‘nationalist’ nature of space programmes around the world, traditionally focused on unaligned useful space applications. It seems that China, India, in the future South Korea, Malaysia and others will set themselves objectives of a more political colouring symbolising national pride in their programmes. At the same time, some countries, like Iran, make no attempt to hide their plans to have their own space defence capabilities. The absolute pre-eminence of the USA, Russia and Europe is starting to fade. For emerging countries space resources are becoming an integral component of their strategic position or an asymmetrical capability aimed at weakening the credibility of advantages held by potential rivals. This article examines the new context and the role that various countries are playing in it. It is how space policies should be determined in order to understand their politico-strategic determinants and to highlight their characteristics. Nevertheless, the competitive spirit is not the only possible way. Permanent space infrastructures could also be organised globally, as ‘global public goods’, to contribute to answering questions related to major issues facing humanity.     

Production of hydrocarbons and nitriles by electrical processes in Titan's atmosphere.

Although lightning has not been observed in Titan's atmosphere, the presence of methane rain in the troposphere suggests the possibility of electrical activity in the form of corona and/or lightning discharges. Here we examine the chemical effects of these electrical processes on a Titan simulated atmosphere composed of CH4 in N2 at various mixing ratios. Corona discharges were simulated in two different experimental arrays. For the detection of reactive intermediates we used a mass spectrometer to study the main positive ions arising by bombarding low-energy electrons from a hot filament into low-pressure methane. The final stable products, generated by applying a high voltage in a coaxial reactor with either positive or negative polarity, were separated and detected by gas chromatography-Fourier transform infrared spectroscopy and electron impact mass spectrometry (GC-FTIR-MS). Lightning discharges were simulated by a hot and dense plasma generated by a Nd-YAG laser and the final products were separated and detected by GC-FTIR-MS. Corona discharges produce linear and branched hydrocarbons as well as nitriles whereas lightning discharges generate mainly unsaturated hydrocarbons and nitriles. Lightning discharges are about 2 orders of magnitude more efficient in product formation than corona discharges.     

Geometric problem solving with strings and pins

Humans solve spatial and abstract problems more easily if these can be visualized and/or physically manipulated. We analyze the domain of geometric problem solving from a cognitive perspective and identify several levels of domain abstraction that interact in the problem solving process. We discuss the roles of physical manifestations of spatial configurations, their manipulation, and their perception for understanding problem solving processes. We propose an extension of the classical problem solving repertoire of constructive geometry to approach certain problems more directly than under the compass-and-straightedge paradigm. Specifically, we introduce strings and pins as helpful metaphors for a generalization of the constructive geometry approach. We present classical problems from spatial problem solving to illustrate the ‘strings and pins’ paradigm. Three case studies are discussed: strings-and-pins solutions to (i) the ellipse construction problem; (ii) the shortest path problem; and (iii) the angle trisection problem. Comparisons to formal solutions are drawn. Differences and similarities between the compass-and-straightedge paradigm and the strings-and-pins paradigm are analyzed. Features and limitations of constructive and depictive geometry as well as implications for computational approaches are discussed. The strings-and-pins domain is shown to be more general and less restrictive than the compass-and-straightedge domain.     

Temporal variation and asymmetry of sunspot and solar plage types from 1930 to 1936

Using the recently converted to digital format heliophysics catalogues of the Ebro Observatory published in the 1930s, we analyse simultaneously the temporal variation and asymmetry of two different solar structures located at different layers of the solar atmosphere: sunspots and solar plages. In particular, we do the research for all the types of sunspots and plages, including the daily and relative frequencies over the solar cycle. The data were catalogued using the sunspot Cortie classification and a solar plage classification scheme proposed by the Ebro Observatory, which group the phenomena by size and shape. For all types of both sunspots and plages, we observe a decrease in their frequency up to the end of solar cycle 16 and an increase over the beginning of solar cycle 17. Furthermore, we note that small sunspot groups are more likely to happen than bigger groups, although single big spots dominate near the solar minimum. The daily frequency of solar plage occurrences shows that there is not a dominance of compact or scattered solar plages. The North-South occurrence distribution of every type in both sunspots and solar plages shows an asymmetry during the solar cycle: in its declining phase, such asymmetry is directed to the north, while in the beginning of a new cycle is directed to the south.