Quantum Communication Uplink to a 3U CubeSat: Feasibility & Design

Satellites are the efficient way to achieve global scale quantum communication (Q.Com) because unavoidable losses restrict fiber based Q.Com to a few hundred kilometers. We demonstrate the feasibility of establishing a Q.Com uplink with a tiny 3U CubeSat (measuring just 10X10X32 cm^3 ) using commercial off-the-shelf components, the majority of which have space heritage. We demonstrate how to leverage the latest advancements in nano-satellite body-pointing to show that our 4kg CubeSat can provide performance comparable to much larger 600kg satellite missions. A comprehensive link budget and simulation was performed to calculate the secure key rates. We discuss design choices and trade-offs to maximize the key rate while minimizing the cost and development needed. Our detailed design and feasibility study can be readily used as a template for global scale Q.Com.Comment: 24 pages, 9 figures, 2 tables. Fixed tables and figure

Widespread winners and narrow-ranged losers: land use homogenizes biodiversity in local assemblages worldwide

Human use of the land (for agriculture and settlements) has a substantial negative effect on biodiversity globally. However, not all species are adversely affected by land use, and indeed, some benefit from the creation of novel habitat. Geographically rare species may be more negatively affected by land use than widespread species, but data limitations have so far prevented global multi-clade assessments of land-use effects on narrow-ranged and widespread species. We analyse a large, global database to show consistent differences in assemblage composition. Compared with natural habitat, assemblages in disturbed habitats have more widespread species on average, especially in urban areas and the tropics. All else being equal, this result means that human land use is homogenizing assemblage composition across space. Disturbed habitats show both reduced abundances of narrow-ranged species and increased abundances of widespread species. Our results are very important for biodiversity conservation because narrow-ranged species are typically at higher risk of extinction than widespread species. Furthermore, the shift to more widespread species may also affect ecosystem functioning by reducing both the contribution of rare species and the diversity of species’ responses to environmental changes among local assemblages

The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts

Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species’ threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project – and avert – future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups – including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems – www.predicts.org.uk). We make site-level summary data available alongside this article. The full database will be publicly available in 2015

Numerical simulation of SMART-1 Hall-thruster plasma interactions

SMART-1 has been the first European mission using a Hall thruster to reach the moon. An onboard plasma diagnostic package allowed a detailed characterization of the thruster exhaust plasma and its interactions with the spacecraft. Analysis of in-flight data revealed, amongst others, an unpredicted large cyclic variation of the spacecraft floating potential and a mysterious asymmetry in the plasma surrounding the spacecraft. To investigate the details of the anomalies, we developed the numerical software tool SmartPIC to characterize and predict spacecraft-plasma interactions. Technical details, such as solar arrays and onboard diagnostic devices, have been modeled with high accuracy. All basic plasma parameters, the spacecraft floating potential, backflow distributions, and ion impact energies are calculated by the code and are available in high spatial resolution throughout the computational domain containing the entire satellite. It was possible to clearly identify the rotating solar cells arrays as the source of the cyclic variation of the spacecraft floating potential. Furthermore, the asymmetry of the plasma formation around the spacecraft is linked to the location of the neutralizer causing a region of increased charge-exchange collisions particle generation. Both of these results have significant impact on the implementation of electric propulsion systems on satellites

Micropulsion Developments at AIT

The increasing application of micro-satellites (from 10 kg up to 100 kg) as well as CubeSats for a rising number of various missions demands the development of miniaturized propulsion systems. The Austrian Institute of Technology is developing a number of micropropulsion technologies including both electric and chemical thrusters targeting high-performance at small scales. Our electric propulsion developments include FEEP thrusters with thrust ranges from μN to mN using highly-integrated clusters of indium Liquid-Metal-Ion Sources providing ultralow thrust noise and long-term stability, as well as the development of a micro PPT thruster enabling pointing capabilities for CubeSats. For chemical thrusters, we are developing novel micro-monopropellant thrusters with several hundred mN as well as a 1-3 N bi-propellant micro rocket engine using green propellants and high specific impulse performance. This paper will give an overview of our micropropulsion developments highlighting performance as well as possible applications.Energie-Umweltmanagemen

MICRO-PROPULSION AND POWER DEVELOPMENTS AT AIT

Abstract: The increasing application of micro-satellites (from 10 kg up to 100 kg) as well as CubeSats for a rising number of various missions demands the development of miniaturized propulsion a power systems. Our department at the Austrian Institute of Technology is developing a number of micropropulsion technologies including both electric (FEEP and µPPTs) and micro chemical thrusters (mono and bi-propellant) targeting highperformance at small scales. Also a micro turbine, a compact thermoacoustic Stirling engine as well as a novel hydrogen storage system based on microspheres is under development promising novel power conversion solutions at small scales

Metal Hydrides as Hydrogen and Heat Storage System for Satellite Applications

HFC Hydrogen and Fuel Cells Conference 201

Characterization of the Reversible Hydrogenation Properties of Sodium Alanate under various contaminated Hydrogen Conditions

HFC Hydrogen and Fuel Cells Conference 201