Time filter

Source Type

Genin L.,Astrium Satellites | Genin L.,ONERA | Champagnat F.,ONERA | Le Besnerais G.,ONERA
Applied Optics | Year: 2012

This paper deals with point target detection in nonstationary backgrounds such as cloud scenes in aerial or satellite imaging. We propose an original spatial detection method based on first- and second-order modeling (i.e., mean and covariance) of local background statistics.We first show that state-of-the-art nonlocal denoising methods can be adapted with minimal effort to yield edge-preserving background mean estimates. These mean estimates lead to very efficient background suppression (BS) detection. However, we propose that BS be followed by a matched filter based on an estimate of the local spatial covariance matrix. The identification of these matrices derives from a robust classification of pixels in classes with homogeneous second-order statistics based on a Gaussian mixture model. The efficiency of the proposed approaches is demonstrated by evaluation on two cloudy sky background databases. © 2012 Optical Society of America.

Zanon O.,Astrium Satellites
Simulation Series | Year: 2011

Astrium Satellites has developed a simulation infrastructure called SimTG. A modeling language was to be chosen to ease the development of simulation models running on SimTG. Thus a domain specific language dedicated to space simulation has been defined. The article will present its main features and the workbench support that has been developed around it.

Mora N.,Ecole Polytechnique Federale de Lausanne | Rachidi F.,Ecole Polytechnique Federale de Lausanne | Pelissou P.,Astrium Satellites | Junge A.,European Space Agency
IEEE Transactions on Electromagnetic Compatibility | Year: 2015

In this paper, we present general considerations for the application of the multiconductor transmission-line theory for simulating shielded spacecraft harness cable assemblies. Some of the practical issues that occur in the modeling process of various components of cable assemblies in spacecraft applications, namely connectors, pigtails, and backshells are discussed. The overall transfer impedance of the assembly measured through a current injection with a pseudomicrostrip line is used as a figure of merit to evaluate the total shielding provided by the harness. Some of the parameters of the model were available from the manufacturers' datasheets, while others were determined either experimentally or empirically. The position of the cables along the cross section was randomly assigned by the simulation tool. In general, the obtained simulation results are found to be in reasonable agreement with the experimental data. It is found that the generally overlooked contact impedances between the cable shields and connectors play a significant role, especially at low frequencies. The presented simulation results also emphasize the importance of the inductance and resistance of the connector backshell interconnection to the spacecraft chassis. © 1964-2012 IEEE.

Scouarnec D.,Astrium Satellites France | Stirland S.,Astrium Satellites | Wolf H.,Airbus
Proceedings of the 2013 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, IEEE APWC 2013 | Year: 2013

Starting from Current state of the art of antenna products flown on Telecommunication satellites - UHF to KA band-, the review of the future mission needs is translated into requirements for antenna product evolutions. Passive and active antenna solutions are discussed, the latter offering increased coverage and power flexibility expressed by commercial operators. Main trends are presented, discussing the current limitations of technology and the required developments enabling the related products to be flown on commercial applications Accommodation and validation of those new products at satellite level are illustrated in the last section of the paper. © 2013 IEEE.

Widder J.,Vienna University of Technology | Biely M.,Ecole Polytechnique Federale de Lausanne | Gridling G.,Vienna University of Technology | Weiss B.,Vienna University of Technology | Blanquart J.-P.,Astrium Satellites
Distributed Computing | Year: 2012

We consider the problem of reaching agreement in distributed systems in which some processes may deviate from their prescribed behavior before they eventually crash. We call this failure model "mortal Byzantine". After discussing some application examples where this model is justified, we provide matching upper and lower bounds on the number of faulty processes, and on the required number of rounds in synchronous systems. We then continue our study by varying different system parameters. On the one hand, we consider the failure model under weaker timing assumptions, namely for partially synchronous systems and asynchronous systems with unreliable failure detectors. On the other hand, we vary the failure model in that we limit the occurrences of faulty steps that actually lead to a crash in synchronous systems. © The Author(s) 2011.

Discover hidden collaborations