Approximate qualitative spatial reasoning

Qualitative relations between spatial regions play an importantrole in the representation and manipulation of spatial knowledge.The RCC5 and RCC8 systems of relations,used in the Region-Connection Calculus, are of fundamentalimportance. These two systems deal with ideal regions havingprecisely determined location. However,in many practical examples of spatial reasoning,regions are represented by finite approximations rather than known precisely.Approximations may be given by describing how a regionrelates to cells forming a partition of the space underconsideration. Although the RCC5 and RCC8 systems have beengeneralized to ``egg-yolk' regions, in order to modelcertain types of vagueness, their extension to regionsapproximated in this way has not been discussed before.This paper presents two methods, the syntactic and the semantic, by which the RCC5 and RCC8 systemsmay be defined for approximate regions. The syntactic uses algebraicoperations on approximate regions which generalize operations on preciseregions. The semantic method makes use of the set of preciseregions which could be the intended interpretation of anapproximate region. Relationships between these two methods arediscussed in detail.alternative to navigation training with a map.     

The chromosphere-corona transition zone above an active region

Intensities and profiles of ion emission lines between 1170 A and 1700 A from an active region on the Sun are measured from spectra obtained with the Naval Research Laboratory's High Resolution Telescope and Spectrograph - HRTS. The measurements provide simultaneous determination of line intensities, wavelength shifts and Doppler widths at 50 separate positions in the active region, with spatial resolution of 1 arc second and spectral resolution 0.07 A. Fine structure variation of intensities and gas flow velocities in the temperature range 20,000–200,000 K are determined. The density sensitive line pair I(1486 N IV)/I(1548 C IV) has been used to measure electron pressures. Derived emission measures imply filling factors of 0.05–0.1 to balance the divergence of conductive flux width radiative losses above 60,000 K.     

Controlled-root formulation for digital phase-locked loops

In a new formulation for digital phase-locked loops, loop-filter constants are determined from loop roots that can each be selectively placed in the s-plane on the basis of a new set of parameters, each with single and direct physical meaning in terms of loop noise band, width root-specific decay rate, or root-specific damping. Loops of first to fourth order are treated in the continuous-update approximation (B_L T→0) and in a discrete-update formulation with arbitrary B _LT. Deficiencies of the continuous-update approximation in large-B_LT applications are avoided in the new discrete-update formulation. A new method for direct, transient-free acquisition with third- and fourth-order loops can improve the versatility and reliability of acquisition with such loops     

The EU's emergent space diplomacy

Science and technology (S&T) have always been at the heart of the European political construction. This started in the Cold War through a series of pan-European collaborative schemes in a panoply of different scientific fields like molecular biology and nuclear research. However, while most of these early collaborative patterns focused on intra-European cooperation, in the post-Cold War era international S&T relations have evolved to encompass a broader international dimension. The European Union is now building a diverse and robust network of cooperation with non-EU partners to become a centre of gravity in international S&T affairs. This increasing linkage between S&T and foreign policy is particularly explicit in space activities. Even though it is the newest space actor in Europe, the EU is pushing the continent to extend the scope of its partnerships with Russia and China, while at the same time modifying its relations with the traditional European partner, the USA, illustrating therefore the emergence of a distinct “EU space diplomacy”.     

Developing new launch vehicle technology: The case for multi-national private sector cooperation

Space is now a global business, yet the cost of getting to space is still high. Developing new launch vehicles that are cheaper, safer, and more reliable is the key to both rapid commercial growth and to more and better government uses of space. However, the R&D process leading to new launch vehicles is expensive and technically challenging; the past 50 years have seen many government development programs, but no major technological breakthroughs. Perhaps, it is therefore time to think about other ways of developing new launch vehicles. The best expertise in this field resides primarily with private companies and is spread across many actors and nations. A consortium led by space firms might be a better approach to opening up space in the 21st century. Governments will have to develop new policies treating space as though it were a commercial industry, in particular, relaxing export trade restrictions wherever possible. Issues of dual-use may be outweighed by the rapidly growing widespread availability of launch capabilities. Since new launch vehicles will require large up-front R&D expenditures, government support will continue to be needed to supplement private capital funds. Contributions to this effort should be international. However, difficult it might be in today's security conscious environment to reorient government policy, doing so may offer the most efficient and successful way to break the technological and economic barriers to more reliable access to space.     

Organ shielding and doses in Low-Earth orbit calculated for spherical and anthropomorphic phantoms

Humans in space are exposed to elevated levels of radiation compared to ground. Different sources contribute to the total exposure with galactic cosmic rays being the most important component. The application of numerical and anthropomorphic phantoms in simulations allows the estimation of dose rates from galactic cosmic rays in individual organs and whole body quantities such as the effective dose. The male and female reference phantoms defined by the International Commission on Radiological Protection and the hermaphrodite numerical RANDO phantom are voxel implementations of anthropomorphic phantoms and contain all organs relevant for radiation risk assessment. These anthropomorphic phantoms together with a spherical water phantom were used in this work to translate the mean shielding of organs in the different anthropomorphic voxel phantoms into positions in the spherical phantom. This relation allows using a water sphere as surrogate for the anthropomorphic phantoms in both simulations and measurements. Moreover, using spherical phantoms in the calculation of radiation exposure offers great advantages over anthropomorphic phantoms in terms of computational time.     

The Ultraviolet Spectrograph on NASA’s Juno Mission

The ultraviolet spectrograph instrument on the Juno mission (Juno-UVS) is a long-slit imaging spectrograph designed to observe and characterize Jupiter’s far-ultraviolet (FUV) auroral emissions. These observations will be coordinated and correlated with those from Juno’s other remote sensing instruments and used to place in situ measurements made by Juno’s particles and fields instruments into a global context, relating the local data with events occurring in more distant regions of Jupiter’s magnetosphere. Juno-UVS is based on a series of imaging FUV spectrographs currently in flight—the two Alice instruments on the Rosetta and New Horizons missions, and the Lyman Alpha Mapping Project on the Lunar Reconnaissance Orbiter mission. However, Juno-UVS has several important modifications, including (1) a scan mirror (for targeting specific auroral features), (2) extensive shielding (for mitigation of electronics and data quality degradation by energetic particles), and (3) a cross delay line microchannel plate detector (for both faster photon counting and improved spatial resolution). This paper describes the science objectives, design, and initial performance of the Juno-UVS.     

How Galactic Cosmic Ray models affect the estimation of radiation exposure in space

The radiation environment in space is a major concern for human spaceflight because of the adverse effects of high levels of radiation on astronauts’ health. Therefore, it is essential to perform radiation risk assessments already during the concept studies of a manned mission. Galactic Cosmic Rays (GCR) have been identified to be one of the primary sources of radiation exposure in space.     

Influence of ionospheric perturbations in GPS time and frequency transfer

The stability of GPS time and frequency transfer is limited by the fact that GPS signals travel through the ionosphere. In high precision geodetic time transfer (i.e. based on precise modeling of code and carrier phase GPS data), the so-called ionosphere-free combination of the code and carrier phase measurements made on the two frequencies is used to remove the first-order ionospheric effect. In this paper, we investigate the impact of residual second- and third-order ionospheric effects on geodetic time transfer solutions i.e. remote atomic clock comparisons based on GPS measurements, using the ATOMIUM software developed at the Royal Observatory of Belgium (ROB). The impact of third-order ionospheric effects was shown to be negligible, while for second-order effects, the tests performed on different time links and at different epochs show a small impact of the order of some picoseconds, on a quiet day, and up to more than 10 picoseconds in case of high ionospheric activity. The geomagnetic storm of the 30th October 2003 is used to illustrate how space weather products are relevant to understand perturbations in geodetic time and frequency transfer.