709 research outputs found
IPv6 and IPsec Tests of a Space-Based Asset, the Cisco Router in Low Earth Orbit (CLEO)
This report documents the design of network infrastructure to support testing and demonstrating network-centric operations and command and control of space-based assets, using IPv6 and IPsec. These tests were performed using the Cisco router in Low Earth Orbit (CLEO), an experimental payload onboard the United Kingdom--Disaster Monitoring Constellation (UK-DMC) satellite built and operated by Surrey Satellite Technology Ltd (SSTL). On Thursday, 29 March 2007, NASA Glenn Research Center, Cisco Systems and SSTL performed the first configuration and demonstration of IPsec and IPv6 onboard a satellite in low Earth orbit. IPv6 is the next generation of the Internet Protocol (IP), designed to improve on the popular IPv4 that built the Internet, while IPsec is the protocol used to secure communication across IP networks. This demonstration was made possible in part by NASA s Earth Science Technology Office (ESTO) and shows that new commercial technologies such as mobile networking, IPv6 and IPsec can be used for commercial, military and government space applications. This has direct application to NASA s Vision for Space Exploration. The success of CLEO has paved the way for new spacebased Internet technologies, such as the planned Internet Routing In Space (IRIS) payload at geostationary orbit, which will be a U.S. Department of Defense Joint Capability Technology Demonstration. This is a sanitized report for public distribution. All real addressing has been changed to psueco addressing
Use of the Delay-Tolerant Networking Bundle Protocol from Space
The Disaster Monitoring Constellation (DMC), constructed by Survey Satellite Technology Ltd (SSTL), is a multisatellite Earth-imaging low-Earth-orbit sensor network where captured image swaths are stored onboard each satellite and later downloaded from the satellite payloads to a ground station. Store-and-forward of images with capture and later download gives each satellite the characteristics of a node in a Delay/Disruption Tolerant Network (DTN). Originally developed for the Interplanetary Internet, DTNs are now under investigation in an Internet Research Task Force (IRTF) DTN research group (RG), which has developed a bundle architecture and protocol. The DMC is currently unique in its adoption of the Internet Protocol (IP) for its imaging payloads and for satellite command and control, based around reuse of commercial networking and link protocols. These satellites use of IP has enabled earlier experiments with the Cisco router in Low Earth Orbit (CLEO) onboard the constellation's UK-DMC satellite. Earth images are downloaded from the satellites using a custom IPbased high-speed transfer protocol developed by SSTL, Saratoga, which tolerates unusual link environments. Saratoga has been documented in the Internet Engineering Task Force (IETF) for wider adoption. We experiment with use of DTNRG bundle concepts onboard the UKDMC satellite, by examining how Saratoga can be used as a DTN convergence layer to carry the DTNRG Bundle Protocol, so that sensor images can be delivered to ground stations and beyond as bundles. This is the first successful use of the DTNRG Bundle Protocol in a space environment. We use our practical experience to examine the strengths and weaknesses of the Bundle Protocol for DTN use, paying attention to fragmentation, custody transfer, and reliability issues
Generalised growth models for aquatic species with an application to blacklip abalone (Haliotis rubra)
This paper presents a maximum likelihood method for estimating growth parameters for an aquatic species that incorporates growth covariates, and takes into consideration multiple tag-recapture data. Individual variability in asymptotic length, age-at-tagging, and measurement error are also considered in the model structure. Using distribution theory, the log-likelihood function is derived under a generalised framework for the von Bertalanffy and Gompertz growth models. Due to the generality of the derivation, covariate effects can be included for both models with seasonality and tagging effects investigated. Method robustness is established via comparison with the Fabens, improved Fabens, James and a non-linear mixed-effects growth models, with the maximum likelihood method performing the best. The method is illustrated further with an application to blacklip abalone ( Haliotis rubra) for which a strong growth-retarding tagging effect that persisted for several months was detected
Observational evidence of dissipative photospheres in gamma-ray bursts
The emission from a gamma-ray burst (GRB) photosphere can give rise to a
variety of spectral shapes. The spectrum can retain the shape of a Planck
function or it can be broadened and have the shape of a Band function. This
fact is best illustrated by studying GRB090902B: The main gamma-ray spectral
component is initially close to a Planck function, which can only be explained
by emission from the jet photosphere. Later, the same component evolves into a
broader Band function. This burst thus provides observational evidence that the
photosphere can give rise to a non-thermal spectrum. We show that such a
broadening is most naturally explained by subphotospheric dissipation in the
jet. The broadening mainly depends on the strength and location of the
dissipation, on the magnetic field strength, and on the relation between the
energy densities of thermal photons and of the electrons. We suggest that the
evolution in spectral shape observed in GRB090902B is due to a decrease of the
bulk Lorentz factor of the flow, leading to the main dissipation becoming
subphotospheric. Such a change in the flow parameters can also explain the
correlation observed between the peak energy of the spectrum and low-energy
power law slope, alpha, a correlation commonly observed in GRBs. We conclude
that photospheric emission could indeed be a ubiquitous feature during the
prompt phase in GRBs and play a decisive role in creating the diverse spectral
shapes and spectral evolutions that are observed.Comment: Submitted to MNRAS, 14 pages, 7 figure
Sushi in the United States, 1945-1970
Sushi first achieved widespread popularity in the United States in
the mid-1960s. Many accounts of sushi’s US establishment foreground
the role of a small number of key actors, yet underplay
the role of a complex web of large-scale factors that provided the
context in which sushi was able to flourish. This article critically
reviews existing literature, arguing that sushi’s US popularity
arose from contingent, long-term, and gradual processes. It examines
US newspaper accounts of sushi during 1945–1970, which
suggest the discursive context for US acceptance of sushi was
considerably more propitious than generally acknowledged.
Using California as a case study, the analysis also explains
conducive social and material factors, and directs attention to
the interplay of supply- and demand-side forces in the favorable
positioning of this “new” food. The article argues that the US
establishment of sushi can be understood as part of broader
public acceptance of Japanese cuisine
Observing the Evolution of the Universe
How did the universe evolve? The fine angular scale (l>1000) temperature and
polarization anisotropies in the CMB are a Rosetta stone for understanding the
evolution of the universe. Through detailed measurements one may address
everything from the physics of the birth of the universe to the history of star
formation and the process by which galaxies formed. One may in addition track
the evolution of the dark energy and discover the net neutrino mass.
We are at the dawn of a new era in which hundreds of square degrees of sky
can be mapped with arcminute resolution and sensitivities measured in
microKelvin. Acquiring these data requires the use of special purpose
telescopes such as the Atacama Cosmology Telescope (ACT), located in Chile, and
the South Pole Telescope (SPT). These new telescopes are outfitted with a new
generation of custom mm-wave kilo-pixel arrays. Additional instruments are in
the planning stages.Comment: Science White Paper submitted to the US Astro2010 Decadal Survey.
Full list of 177 author available at http://cmbpol.uchicago.ed
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Spirit, mind and body: the archaeology of monastic healing
Archaeology and material culture are used in this chapter to consider how monastic experience responded to illness, ageing and disability. The approach taken is influenced by the material study of religion, which interrogates how bodies and things engage to construct the sensory experience of religion, and by practice-based approaches in archaeology, which examine the active role of space and material culture in shaping religious agency and embodiment. The archaeology of monastic healing focuses on the full spectrum of healing technologies, from managing the body in order to prevent illness, through to the treatment of the sick and preparation of the corpse for burial
The twilight of the Liberal Social Contract? On the Reception of Rawlsian Political Liberalism
This chapter discusses the Rawlsian project of public reason, or public justification-based 'political' liberalism, and its reception. After a brief philosophical rather than philological reconstruction of the project, the chapter revolves around a distinction between idealist and realist responses to it. Focusing on political liberalism’s critical reception illuminates an overarching question: was Rawls’s revival of a contractualist approach to liberal legitimacy a fruitful move for liberalism and/or the social contract tradition? The last section contains a largely negative answer to that question. Nonetheless the chapter's conclusion shows that the research programme of political liberalism provided and continues to provide illuminating insights into the limitations of liberal contractualism, especially under conditions of persistent and radical diversity. The programme is, however, less receptive to challenges to do with the relative decline of the power of modern states
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