World's first ZigBee-based inter-satellite comms system

This image depicts VELOX-I before and after deployment and a picosatellite. Credit: Shuanglong Xie, Guo Xiong Lee, Kay-Soon Low, Erry Gunawan, 2014

Engineers at the Nanyang Technological University in Singapore have successfully piloted the world's first ZigBee-based inter-satellite communication system.

The team at the Satellite Research Centre launched the VELOX-I, which consists of a nanosatellite weighing 3.5 kg and a piggyback picosatellite weighing 1.5 kg, from the two highest points on campus. Both miniature satellites were configured with a ZigBee wireless network and equipped with small sensor nodes that perform functions such as local sensing, distributed computing and data-gathering.

Designed to evaluate the performance of wireless sensor networks (WSNs) in space, the experiment marks a breakthrough in aeronautical engineering. After conducting Received Signal Strength Indicator tests on the satellites' radio frequency modules, a maximum range of 1 km was found to be achievable for inter-satellite communication in the campus environment. An even longer communication range can be expected in free space, due to the absence of signal attenuation caused by fading and diffraction.

To estimate the range of inter-satellite communication in free space, the team applied a link budget analysis based on the Friis transmission equation, deriving an average theoretical distance of 4.186 km and a maximum of 15.552 km. Published in the special issue of Unmanned Systems, these findings present a compelling case for further studies into inter-satellite communication systems with more complex designs.

In addition to their high performance in inter-satellite communication, WSNs are also remarkably suitable for intra-satellite communication. The team found that by replacing internally wired connections with wireless links, a satellite's mass could be reduced by as much as 10%. With the twin pressures of minimising development costs and maximising risk diversification imposing major constraints on satellite design, the production of comprehensive yet lightweight systems could benefit significantly from WSNs.

Although WSNs have been used in a wide range of applications in recent years, their use in space applications has, until now, remained limited. The Singaporean team's data-driven survey has established a sound platform for future formation-flying satellite missions, and seems poised to create subsequent revolutions in space.

Source: World Scientific

Easy measurement of the effect of fine dust

The Karlsruhe Exposure System is compact and can measure fine dust concentrations directly at the location of pollution. Credit: VITROCELL Systems GmbH

Fine dusts from industry, traffic, and households are omnipresent. Still, they are difficult to capture by reliable medical measurements. KIT researchers have now developed an exposure system, by means of which biological cells are exposed to fine dust-loaded air flows in an exact and reproducible manner. Using this system, it is possible to collect data on the adverse impact of fine dusts of variable sources in a rapid and inexpensive manner and without animal experiments being needed. In cooperation with the industry partner Vitrocell, a marketable product has been developed.

"Fine dusts may be carbon black from diesel engines, sea salt on the coast, natural dusts, or intermediate products of chemical industry," Dr. Hanns-Rudolf Paur and Sonja Mülhopt of Karlsruhe Institute of Technology explain. All dust grains smaller than 10 µm, i.e. one hundredth of a millimeter, are considered to be fine dust irrespective of their chemical composition. Dust particles smaller than 10 µm easily pass the upper respiratory tract of man. "They deposit in the pulmonary alveoli and may damage the lungs due to their chemical or physical properties."

To study the effects in detail, lung cells and fine dust have to be brought together in a realistic environment. Ultimately, the processes taking place in the human body from the nose to the lungs have to be reproduced. For this purpose, the air containing the fine dust is heated up to body temperature by the Karlsruhe Exposure System. The air flow is provided with about 85% humidity and reduced to the air flow rate of the lungs. For a long-term measurement series, these conditions have to be maintained exactly and reproducibly. Finally, the particle flow passes lung cell cultures cultivated with nutrient medium. 

Depending on the type of fine dust, these cultures subsequently show symptoms of inflammation, oxidation stress, or membrane damage. In parallel, the deposited particle dose is recorded by means of a precision balance.

The new Exposure System is much closer to reality than previous methods that collected fine dust from air or exhaust gas and stirred it into the nutrient liquid. At the same time, the Exposure System works more rapidly for many applications and is cheaper than a study based on animal experiments. Thanks to its compactness, the Karlsruhe Exposure System can also be used for measurements at the place of fine dust development or pollution. "The limitations of conventional methods were overcome by the close, interdisciplinary cooperation of biologists and process engineers at KIT," the Head of the project, Sonja Mülhopt, says. "With the Karlsruhe Exposure System, we now have a technology that will improve the protection of the environment and mankind."

"Research at KIT was the basis of a process with a high industry potential," Tobias Krebs of the company Vitrocell Systems (Waldkirch) says. "Together, we now plan to commercialize this product." The impact of fine dusts plays an important role in fundamental research as well as in many areas of application. According to the EU Directive on Chemicals REACH, chemical industry is obliged to classify its products in various hazard categories. 

Manufacturers of lung medicine, such as asthma sprays, are now enabled to test new substances in a close-to-reality manner. New and old biomass fuels may also be relevant fine dust sources.

Source:  Karlsruhe Institute of Technology