Water Vapor Independent Satellite Propulsion System (WISP) for Nanosatellite Orbit Maintenance

While nanosatellites have been widely implemented for scientific applications, power constraints, large free-space path losses, and system complexity prevent many researchers from fielding novel sensing hardware. Additionally, dead-on-arrival missions contribute to the growing volume of orbital debris. Access to lower orbits would decrease downlink losses, improve optical sensor performance, and ensure natural de-orbit for inoperable payloads. Conventional satellite propulsion technologies are capable of providing thrust required to maintain a low orbit, but increase system complexity and draw power away from the sensors. The United States Naval Academy has developed the Water Vapor Independent Satellite Propulsion system (WISP) to maintain orbits as low as 250km without drawing electrical power during steady state operation. This system utilizes an aqueous methyl alcohol propellant that passively evaporates across a phase separation boundary prior to exiting through a nozzle. Since this process occurs passively based on propellant evaporation properties and expansion chamber conditions, no electrical power is required during steady state operation. Theoretical calculations show that this system of 1U volume (10 x 10 x 10cm) is capable of providing sufficient thrust to maintain orbit for approximately 30 days

Aerodynamic Stabilization with a Drag-Makeup Propulsion Unit for Very Low Earth Orbit

Power constraints, large RF free-space path losses, and system complexity prevent many researchers from fielding novel sensing hardware aboard nanosatellite missions. Access to lower orbits would decrease downlink losses, improve optical sensor performance, and ensure natural de-orbit for inoperable payloads. Conventional propulsion technologies are capable of providing thrust required to maintain a low orbit but increase system complexity and draw power away from sensors. The United States Naval Academy has developed the Water Vapor Independent Satellite Propulsion system (WISP) to maintain orbits as low as 250km. This system utilizes an aqueous methyl alcohol propellant that passively evaporates across a phase separation boundary, requiring no electrical power during steady state operation. Theoretical calculations show that this system of 1U volume (10 x 10 x 10cm) is capable of providing sufficient thrust to maintain 250km orbit for 3U satellite for approximately 30 days

Space Mobile Network (SMN) User Demonstration Satellite (SUDS) for a Practical On-Orbit Demonstration of User Initiated Services (UIS)

This paper will discuss the various aspects of implementation of the Space Mobile Network (SMN) architecture framework within the context of operations of various nodes equipped with the User Initiated Services (UIS) protocol. These aspects include development of a Client-Server architecture in which space based Clients can create links with ground based Servers to negotiate passes with ground stations or contacts with the Tracking and Data Relay Satellite (TDRS) fleet. A key feature of this concept is that Users may require a mix of low data rate continuous contacts with one or more of the TDRS fleet and sporadic contacts with ground stations as passes become available. SUDS (SMN User Demonstration Satellite) will have the availability of TDRS contacts, the U.S. Naval Academy's ground station, NASA Near Earth Network ground sites and others. This mode of operations must be integrated within the traditional mode of scheduling contacts and passes. Thus, SUDS fits into a heterogeneous network operations concept of operations

Voter decision-making in a context of low political trust: the 2016 UK EU membership referendum

Using volunteer writing for Mass Observation, we explore how British citizens decided whether to leave the EU. The 2016 referendum was the biggest decision made by the British electorate in decades, but involved limited voter analysis. Many citizens did not have strong views about EU membership in early 2016. The campaigns did not help to firm up their views, not least because so much information appeared to be in dispute. Voters, often characterised as polarised, were reluctant and uncertain. Many citizens took their duty to decide seriously, but were driven more by hunch than careful analysis. In 2016, voters reacted against elites they did not trust at least as much as they embraced the ideas of trusted elites. This contrasts with the 1975 Referendum on the Common Market, when the vote was driven by elite endorsement. In low-trust contexts, voters use cues from elites as negative rather than positive stimulus

Association between fast food purchasing and the local food environment

Objective: In this study, an instrument was created to measure the healthy and unhealthy characteristics of food environments and investigate associations between the whole of the food environment and fast food consumption.Design and subjects: In consultation with other academic researchers in this field, food stores were categorised to either healthy or unhealthy and weighted (between +10 and &minus;10) by their likely contribution to healthy/unhealthy eating practices. A healthy and unhealthy food environment score (FES) was created using these weightings. Using a cross-sectional study design, multilevel multinomial regression was used to estimate the effects of the whole food environment on the fast food purchasing habits of 2547 individuals.Results: Respondents in areas with the highest tertile of the healthy FES had a lower likelihood of purchasing fast food both infrequently and frequently compared with respondents who never purchased, however only infrequent purchasing remained significant when simultaneously modelled with the unhealthy FES (odds ratio (OR) 0.52; 95% confidence interval (CI) 0.32&ndash;0.83). Although a lower likelihood of frequent fast food purchasing was also associated with living in the highest tertile of the unhealthy FES, no association remained once the healthy FES was included in the models. In our binary models, respondents living in areas with a higher unhealthy FES than healthy FES were more likely to purchase fast food infrequently (OR 1.35; 95% CI 1.00&ndash;1.82) however no association was found for frequent purchasing.Conclusion: Our study provides some evidence to suggest that healthier food environments may discourage fast food purchasing.<br /

Europe as a multilevel federation

Peer reviewedPublisher PD

Resilience to obesity among socioeconomically disadvantaged women : the READI study

Objective: This cross-sectional study aimed to identify sociodemographic and behavioural characteristics of &lsquo;overweight-resilient&rsquo; women, that is, women who were in a healthy body weight range, despite living in socioeconomically disadvantaged neighbourhoods that place them at increased risk of obesity. The study also aimed to test a comprehensive theoretically derived model of the associations between intrapersonal, social and environmental factors and obesity among this target group.Participants: A total of 3235 women aged 18&ndash;45 years from 80 urban and rural neighbourhoods throughout Victoria, Australia, participated in the Resilience for Eating and Activity Despite Inequality study.Measurements: Women reported height, weight, sociodemographic characteristics, leisure-time physical activity, dietary behaviours and a range of theoretically derived cognitive, social and neighbourhood environmental characteristics hypothesized to influence obesity risk. A theoretical model predicting body mass index (BMI) was tested using structural equation models.Results: Women classified as &lsquo;resilient&rsquo; to obesity tended to be younger, born overseas, more highly educated, unmarried and to have higher or undisclosed household incomes. They engaged in more leisure-time physical activity and consumed less fast foods and soft drinks than overweight/obese women. Neighbourhood characteristics, social characteristics and cognitive characteristics all contributed to explaining variation in BMI in the hypothesized directions.Conclusions: These results demonstrate several characteristics of women appearing &lsquo;resilient&rsquo; to obesity, despite their increased risk conferred by residing in socioeconomically disadvantaged neighbourhoods. Acknowledging the cross-sectional study design, the results advance theoretical frameworks aimed at investigating obesity risk by providing evidence in support of a comprehensive model of direct and indirect effects on obesity of neighbourhood, as well as social, cognitive and behavioural characteristics

The Next Generation of NASA Rapid Response: Worldview Snapshots

The NASA Rapid Response system started in 2001 by serving static subsets of Near Real Time MODIS (Moderate Resolution Imaging Spectroradiometer) imagery acquired from the Terra satellite. Over this time, Rapid Response has been used to support near real time applications such as wildfire and sea ice mapping for hundreds of thousands of users. In 2011, the toolset expanded to include GIBS, the Global Imagery Browse Services, which provides a web map tiling service of over 700 imagery products, and Worldview (https://worldview.earthdata.nasa.gov/), an interactive web application that showcases the products available in GIBS. This year a new application, Worldview Snapshots, has been added to complete the toolset by providing a flexible, low bandwidth method to download personalized subsets for those who do not need or cannot use a fully featured web mapping application. The original Rapid Response subset tool has been retired and we thank it for its seventeen years of service. Stop by to learn more about the next generation of NASA Rapid Response

Kiwi Forego Vision in the Guidance of Their Nocturnal Activities

BACKGROUND: In vision, there is a trade-off between sensitivity and resolution, and any eye which maximises information gain at low light levels needs to be large. This imposes exacting constraints upon vision in nocturnal flying birds. Eyes are essentially heavy, fluid-filled chambers, and in flying birds their increased size is countered by selection for both reduced body mass and the distribution of mass towards the body core. Freed from these mass constraints, it would be predicted that in flightless birds nocturnality should favour the evolution of large eyes and reliance upon visual cues for the guidance of activity. METHODOLOGY/PRINCIPAL FINDINGS: We show that in Kiwi (Apterygidae), flightlessness and nocturnality have, in fact, resulted in the opposite outcome. Kiwi show minimal reliance upon vision indicated by eye structure, visual field topography, and brain structures, and increased reliance upon tactile and olfactory information. CONCLUSIONS/SIGNIFICANCE: This lack of reliance upon vision and increased reliance upon tactile and olfactory information in Kiwi is markedly similar to the situation in nocturnal mammals that exploit the forest floor. That Kiwi and mammals evolved to exploit these habitats quite independently provides evidence for convergent evolution in their sensory capacities that are tuned to a common set of perceptual challenges found in forest floor habitats at night and which cannot be met by the vertebrate visual system. We propose that the Kiwi visual system has undergone adaptive regressive evolution driven by the trade-off between the relatively low rate of gain of visual information that is possible at low light levels, and the metabolic costs of extracting that information