Anti-Collision Function Design and Performances of the CNES Formation Flying Experiment on the PRISMA Mission

Within the framework of a partnership agreement, EADS ASTRIUM has worked since June 2006 for the CNES formation flying experiment on the PRISMA mission. EADS ASTRIUM is responsible for the anti-collision function. This responsibility covers the design and the development of the function as a Matlab/Simulink library, as well as its functional validation and performance assessment. PRISMA is a technology in-orbit testbed mission from the Swedish National Space Board, mainly devoted to formation flying demonstration. PRISMA is made of two micro-satellites that will be launched in 2009 on a quasi-circular SSO at about 700 km of altitude. The CNES FFIORD experiment embedded on PRISMA aims at flight validating an FFRF sensor designed for formation control, and assessing its performances, in preparation to future formation flying missions such as Simbol X; FFIORD aims as well at validating various typical autonomous rendezvous and formation guidance and control algorithms. This paper presents the principles of the collision avoidance function developed by EADS ASTRIUM for FFIORD; three kinds of maneuvers were implemented and are presented in this paper with their performances

Review of GPS Collar Deployments and Performance on Nonhuman Primates

Over the past twenty years, GPS collars have emerged as powerful tools for the study of nonhuman primate (hereafter, "primate") movement ecology. As the size and cost of GPS collars have decreased and performance has improved, it is timely to review the use and success of GPS collar deployments on primates to date. Here we compile data on deployments and performance of GPS collars by brand and examine how these relate to characteristics of the primate species and field contexts in which they were deployed. The compiled results of 179 GPS collar deployments across 17 species by 16 research teams show these technologies can provide advantages, particularly in adding to the quality, quantity, and temporal span of data collection. However, aspects of this technology still require substantial improvement in order to make deployment on many primate species pragmatic economically. In particular, current limitations regarding battery lifespan relative to collar weight, the efficacy of remote drop-off mechanisms, and the ability to remotely retrieve data need to be addressed before the technology is likely to be widely adopted. Moreover, despite the increasing utility of GPS collars in the field, they remain substantially more expensive than VHF collars and tracking via handheld GPS units, and cost considerations of GPS collars may limit sample sizes and thereby the strength of inferences. Still, the overall high quality and quantity of data obtained, combined with the reduced need for on-the-ground tracking by field personnel, may help defray the high equipment cost. We argue that primatologists armed with the information in this review have much to gain from the recent, substantial improvements in GPS collar technology

Scénarios de pénétration des réacteurs à neutrons rapides en vue de limiter la consommation d'uranium naturel cumulée

Dans un contexte de croissance modérée de la demande électrique en France (temps de doublement : cent ans), on montre que les réacteurs à neutrons rapides (RNR) peuvent constituer la relève des réacteurs à eau pressurisée (REP) à partir des années 2000, permettant ainsi de limiter à moins de 450 000 t la consommation en uranium naturel cumulée, sous réserve : — qu'ils soient initialement de bons surgénérateurs ; — que le temps de séjour hors pile soit faible (au plus égal à trois ans). Le recyclage du plutonium dans les REP permet d'éviter des fluctuations importantes du stock de plutonium. Cependant, ce recyclage réduit les quantités de plutonium disponibles. De ce fait, le démarrage des RNR est retardé et les besoins en uranium naturel sont augmentés sensiblement. A court terme, un bon convertisseur est une solution de substitution au « recyclage Pu classique », mais non aux RNR ; à long terme, en symbiose avec les RNR, il permet une bonne gestion des stocks de plutonium. La vitesse de croissance du parc RNR nécessite d'avoir un produit industriel dès l'an 2000

The OSCE and the Multiple Challenges of Transition in the Caucasus and Central Asia (1991-2001)

In the wake of 9/11 and the U.S. intervention in Afghanistan, Central Asia and the Caucasus have moved to the forefront of the international political agenda. At the same time, the events since 9/11 have had a major impact on Central Asia and the Caucasus and external actors’ engagement in the region

Effective Hamiltonian approach to doubly degenerate electronic states. I - Theory and applications to E ⊗ (b1 + b2) and related Jahn-Teller systems.

International audienceSeveral problems in vibronic spectroscopy are solved within the effective Hamiltonian formalism combined with Lie algebraic methods. We consider mainly vibronic interactions in orbital doublets for molecules with a principal symmetry axis of order n = 4k (or n even for Dnd symmetry groups). Effective Hamiltonian models for E ⊗ (b1 + b2), E ⊗ (bi + aj) and E ⊗ (bi + e) Jahn-Teller dynamical systems are discussed as well as some correlations with previous studies established

Influence of spore size distribution, gas mixture, and process time on the removal rate of B. subtilis spores in low-pressure plasmas

The size reduction of B. subtilis spores due to removal of biological material in low-pressure plasmas was analyzed in a double inductively coupled plasma system. Argon, nitrogen, and oxygen at 5 Pa were used as feed gases to investigate the impact of different reactive species and high energy radiation on the process. The spore size was determined using scanning electron microscopy images and the length of thousands of spores were evaluated using an automated algorithm. By applying a statistical test the precision of the mean spore size determination was increased and the applicability of a normal distribution to describe the spore size distribution was demonstrated. The removal rate was found to vary depending on the process gas as well as on the process time and was found to be largest with a mixture of nitrogen and oxygen and lowest in pure argon. With increasing treatment time the removal rate decreases significantly and tends to stop in all gases and inhibits the complete removal of spores and potentially hazardous biological material. Possible explanations for this effect are the aggregation of non-volatile compounds or the formation of cross-linked layers which significantly reduce the etching efficiency