Advanced channel coding for space mission telecommand links

We investigate and compare different options for updating the error correcting code currently used in space mission telecommand links. Taking as a reference the solutions recently emerged as the most promising ones, based on Low-Density Parity-Check codes, we explore the behavior of alternative schemes, based on parallel concatenated turbo codes and soft-decision decoded BCH codes. Our analysis shows that these further options can offer similar or even better performance.Comment: 5 pages, 7 figures, presented at IEEE VTC 2013 Fall, Las Vegas, USA, Sep. 2013 Proc. IEEE Vehicular Technology Conference (VTC 2013 Fall), ISBN 978-1-6185-9, Las Vegas, USA, Sep. 201

Weeds for weed control: Asteraceae essential oils as natural herbicides.

The aim of this study was to test the botanical family of Asteraceae as a source of natural herbicides. Twenty Asteraceae species were collected during flowering time and evaluated in terms of the yield and quality of essential oils (germination inhibition and growth of weeds). Half the species showed a sufficient yield of essential oil (from about 0.1% to 1.43%) when testing these phytochemicals in vitro as germination inhibitors of two typical weeds, Amaranthus retroflexus and Setaria viridis. Despite the higher tolerance of S. viridis, the concentration of 100 lg L 1 of essential oils of the two Artemisia species and Xanthium strumarium could totally inhibit germination. In addition, at 10 lg L 1, the same essential oils showed full inhibition of A. retroflexus seeds. A comparison of their effectiveness at suboptimal doses led to a further selection of the most promising sources of essential oils. After their chemical characterisation, the essential oils were tested as post-emergence herbicides on seedlings of the above-cited weeds. After spraying the weeds at different concentrations (10, 100 and 1000 mg L 1) during two different phenological stages of weed seedlings (cotyledons and the third true leaf), the essential oils of Artemisia annua and X. strumarium showed the best performance. The essential oils of X. strumarium were then tested again on both weeds to monitor the dynamics of plant injury. A reduction in plant fresh weight (about 20%–30% after 10 days) and chlorophyll content (destroyed, after the same amount of time) was found, thus confirming the total and rapid effectiveness of these essential oils. In summary, A. annua and X. strumarium have elicited considerable agronomic interest and appear to be suitable as a source of essential oils to act as natural herbicides

Link-Layer Coding for GNSS Navigation Messages

In this paper, we face the problem of ensuring reliability of Global Navigation Satellite Systems (GNSSs) in harsh channel conditions, where obstacles and scatter cause long outage events that cannot be counteracted with channel coding only. Our novel approach, stemming from information-theoretic considerations, is based on link-layer coding (LLC). LLC allows us to significantly improve the efficiency in terms of time-to-first-fix with respect to current operational GNSSs, which adopt carousel transmission. First, we investigate the maximum theoretical LLC gain under different Land Mobile Satellite channel conditions. Then, some practical LLC coding schemes, namely, fountain codes and a novel low-density parity-check plus low-rate repetition coding, are proposed and tested in realistic single-satellite and multi-satellite Land Mobile Satellite scenarios, considering the Galileo I/NAV message as study case. Simulation results show that our designed schemes largely improve on carousel transmission and achieve near-optimal performance with limited increase in complexity. Also, back-compatibility of LLC is assessed with respect to present-time GNSS specifications. © 2018 Institute of Navigation

A highly efficient receiver for satellite-based automatic identification system signal detection

An innovative receiver architecture for the satellite-based automatic identification system has been recently proposed. In this paper, we describe a few modifications that can be introduced on the algorithms for synchronization and detection, which provide an impressive performance improvement. The receiver architecture has been designed for an on-board implementation, and a prototype has been implemented by the University of Parma and CGS S.p.A. Compagnia Generale per lo Spazio under the European Space Agency project FENICE (Flexible innovative AIS receiver prototype). A few modifications are also here described that could allow a further performance improvement in case of processing moved to ground-based stations, based on a priori information there available

A highly efficient receiver for satellite-based Automatic Identification System signal detection

An innovative receiver architecture for the satellitebased Automatic Identification System (AIS) has been recently proposed. In this paper, we describe a few modifications that can be introduced on the algorithms for synchronization and detection, that provide an impressive performance improvement with respect to the previous system. The receiver architecture has been designed for an on-board implementation, and for this reason all algorithms have been realized keeping the complexity as low as possible. A prototype for the proposed receiver has been implemented by the University of Parma and CGS S.p.A. Compagnia Generale per 10 Spazio under the ESA project FENICE

The VMC Survey. XXII. Hierarchical Star Formation in the 30 Doradus-N158-N159-N160 Star-forming Complex

We study the hierarchical stellar structures in a ∼1.5 deg2 area covering the 30 Doradus-N158-N159-N160 star-forming complex with the VISTA Survey of Magellanic Clouds. Based on the young upper main-sequence stars, we find that the surface densities cover a wide range of values, from log(pc2) ≲ -2.0 to log(pc2) ≳ 0.0. Their distributions are highly non-uniform, showing groups that frequently have subgroups inside. The sizes of the stellar groups do not exhibit characteristic values, and range continuously from several parsecs to more than 100 pc; the cumulative size distribution can be well described by a single power law, with the power-law index indicating a projected fractal dimension D2 = 1.6 ± 0.3. We suggest that the phenomena revealed here support a scenario of hierarchical star formation. Comparisons with other star-forming regions and galaxies are also discussed.Fil: Sun, Ning-Chen. Peking University; ChinaFil: Grijs, Richard De. Peking University; ChinaFil: Subramanian, Smitha. Peking University; ChinaFil: Cioni, Maria-Rosa L.. Universita Zu Berlin. Universita Postdam; AlemaniaFil: Rubele, Stefano. Università di Padova; ItaliaFil: Bekki, Kenji. University of Western Australia; AustraliaFil: Ivanov, Valentin D.. European Southern Observatory; ChileFil: Piatti, Andres Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaFil: Ripepi, Vincenzo. Osservatorio Astronomico di Capodimonte; Itali

LTE Adaptation for Mobile Broadband Satellite Networks

n/