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Astronauts are spending longer periods locked up in ships or stations for scientific and exploration spatial missions. The International Space Station (ISS) has been inhabited continuously for more than 20 years and the duration of space stays by crews could lengthen with the objectives of human presence on the moon and Mars. If the environment of these space habitats is designed for the comfort of astronauts, it is also conducive to other forms of life such as embarked microorganisms. The latter, most often associated with surfaces in the form of biofilm, have been implicated in significant degradation of the functionality of pieces of equipment in space habitats. The most recent research suggests that microgravity could increase the persistence, resistance and virulence of pathogenic microorganisms detected in these communities, endangering the health of astronauts and potentially jeopardizing long-duration manned missions. In this review, we describe the mechanisms and dynamics of installation and propagation of these microbial communities associated with surfaces (spatial migration), as well as long-term processes of adaptation and evolution in these extreme environments (phenotypic and genetic migration), with special reference to human health. We also discuss the means of control envisaged to allow a lasting cohabitation between these vibrant microscopic passengers and the astronauts., Biofilm, 5, ISSN:2590-2075

Space-to-Earth telemetry (TM) links have extensively exploited advanced coding schemes, from convolutional codes to Reed-Solomon codes. The Next Generation Uplink Coding Techniques (NEXCODE) study, funded under the Technology Research Program of the European Space Agency (ESA), aimed at research, design, development, and demonstration of a TC receiver chain for scientific missions, including new channel codes. Agencies and researchers investigated and compared a number of possible alternatives, including binary and non-binary LDPC codes even in the presence of jamming. The schemes were evaluated taking into account the peculiar characteristics of TC links in terms of coding gain and complexity. Commands from Earth to space are sent in the payload of TC transfer frames (TFs). A TF is divided into blocks, each as long as 56 bits and individually BCH encoded. The TC transmission protocol includes an additional mechanism that guarantees a minimum number of symbol transitions to keep symbol synchronization. In acquisition mode, the TC standard [15] specifies the use of a symmetric triangular carrier sweeping procedure with the purpose of locking to the carrier frequency. In this stage, the ground station (G/S) transmits an unmodulated carrier whose frequency is swept around the nominal carrier frequency. Carrier tracking in the baseline receiver is performed with a 2nd order PLL, which is compromised in the DS scenario by the noise reduction versus dynamic range trade-off.

International audience; This article proposes an original structure of evanescent quadridge antenna (EQA) to conceive dual-polarized full-metal front-ends that can be used in active antennas (AAs) with wide field-of-view (FoV). An original design methodology is here proposed that allows to induce radiation from subwavelength squared apertures based on the use of evanescent and quadridge waveguides. The proposal is illustrated by means of a design with 4.5% bandwidth providing dual-circular polarization (CP) with good performance up to 50 degrees-scanning even in the diagonal plane. For comparison purposes, a metallic benchmark is also proposed, which is based on the use of classical quadridge horns. Such comparative analysis allows to understand the superior performance of the proposed concept and its main advantage: it allows to avoid the excitation of the first high order mode in the squared quadridge aperture. The excitation of such spurious mode in the antenna is explained in terms of simple equivalent circuit models characterizing the aperture periodic discontinuity.

Earth observation through satellite images is crucial to help economic activities as well as to monitor the impact of human activities on ecosystems. Current satellite systems are subjected to strong computational complexity constraints. Thus, image compression is perfomed onboard with specifically tailored algorithms while image denoising is performed on the ground. In this letter, we intend to address satellite image compression and denoising with neural networks. The first proposed approach uses a single neural architecture for joint onboard compression and denoising. The second proposed approach sequentially uses a first neural architecture for onboard compression and a second one for on ground denoising. For both approaches, the onboard architectures are lightened as much as possible, following the procedure proposed in [1]. The two approaches are shown to outperform the current satellite imaging system and their respective pros and cons are discussed.

International audience; This work presents a new topology of evanescent mode filter (EMF) that allows for its efficient additive manufacturing (AM). Chamfered ridges which avoid the appearance of undesired supports when printed vertically (i.e., along the propagation axis of the filter) are considered. This strategy ensures accurate tolerances, reduced cost and it also enables monolithic manufacturing of the EMF as part of a feed chain. A circuit model is developed to explain the behavior of the new ridges as well as to speed up the overall filter design. The proposed concept and methodology are validated experimentally through the manufacturing and measurement of a prototype.

International audience; Introduction: ESA is currently exploring plans to utilize the European Large Lunar Lander (EL3) for science-driven missions that will allow us to bring about 1.5 tons of payload to the lunar surface. A first mission to a polar landing site is scheduled for 2029. This mission will not carry a rover but subsequent missions in the 2030’s will be more complex and comprehensive and will include a rover. Considering the large payload mass, we explore the scientific potential of a rover that will be able to travel 10s -100s of kilometers, have night survival capabilities, and carry a comprehensive suite of instruments (e.g., LIBS, Raman, IR-spectrometer, multispectral stereo cameras) to characterize and pre-select interesting samples. A novelty of our concept is that we propose to continuously operate certain instruments while roving. For example, a continuously operated ground-penetrating radar would yield information on the sub-surface regolith structure and an IR-spectrometer would produce mineralogical/compositional profiles along rover paths

International audience; Modern space-observation missions demand stringent pointing requirements that motivated a significant amount of research on the topic of microvibration isolation and line-of-sight stabilization systems. While disturbances can be reduced by mounting some of the noisy equipment on various isolation platforms, residual vibrations can still propagate through and be amplified by the flexible structure of the spacecraft. In order to alleviate these issues, the line of sight must also be actively controlled at the payload level. However, such systems typically have to rely solely on low-frequency sensors based on image processing algorithms. The goal of this article is to present a model-based control methodology that can increase the bandwidth of such systems by making use of additional rate sensors mounted on the main disturbance elements impacting the optical path. Following a comprehensive model identification and uncertainty quantification part, the robust control strategy is designed to account for plant uncertainty and provide formal worst case performance guarantees. Excellent agreement between theoretical prediction and experimental results are obtained on a test bench developed at the European Space Agency.

Model-Based Systems Engineering (MBSE) is an adopted modelling and development approach for correct-by- construction of complex software systems, such as space applications. TASTE [1] is a pragmatic and mature MBSE toolset supported by ESA that enables and provides automation for most of the phases of software system development: (i) heterogeneous system design through several modelling and programming languages (e.g., ASN.1, AADL, SDL, C/C++), (ii) code generation, build and deployment of the binary application(s), (iii) validation through static analysis and simulation, and (iv) formal verification of properties by model-checking. The formal verification capabilities have been recently added to the TASTE toolset in the ESA project Model-Checking for Formal Verification of Space Systems (MoC4Space) and validated on two real-life case studies. Within this paper we report on the results and lessons learned during the project.

Monte-Carlo simulations play a key role in most Verification and Validation (V&V) processes. It is however time-consuming and may fail to detect rare worst-case configurations. In such cases, when applicable, µ-analysis offers a nice alternative but does not provide any quantification of the probability of occurrence of the identified worst-cases. A control system can then be invalidated on the basis of unlikely events. Probabilistic µ-analysis was introduced in this context 20 years ago to bridge the gap between the two techniques, but until recently no practical tools were available. This paper summarizes recent advances on this topic. A practical algorithm for probabilistic gain, phase and disk margins analysis is first proposed, and then applied to a satellite high pointing system involving uncertain flexible modes.

CHEOPS Consortium: V. Bourrier et al., Much remains to be understood about the nature of exoplanets smaller than Neptune, most of which have been discovered in compact multi-planet systems. With its inner ultra-short period planet b aligned with the star and two larger outer planets d-c on polar orbits, the multi-planet system HD 3167 features a peculiar architecture and offers the possibility to investigate both dynamical and atmospheric evolution processes. To this purpose we combined multiple datasets of transit photometry and radial velocimetry (RV) to revise the properties of the system and inform models of its planets. This effort was spearheaded by CHEOPS observations of HD 3167b, which appear inconsistent with a purely rocky composition despite its extreme irradiation. Overall the precision on the planetary orbital periods are improved by an order of magnitude, and the uncertainties on the densities of the transiting planets b and c are decreased by a factor of 3. Internal structure and atmospheric simulations draw a contrasting picture between HD 3167d, likely a rocky super-Earth that lost its atmosphere through photo-evaporation, and HD 3167c, a mini-Neptune that kept a substantial primordial gaseous envelope. We detect a fourth, more massive planet on a larger orbit, likely coplanar with HD 3167d-c. Dynamical simulations indeed show that the outer planetary system d-c-e was tilted, as a whole, early in the system history, when HD 3167b was still dominated by the star influence and maintained its aligned orbit. RV data and direct imaging rule out that the companion that could be responsible for the present-day architecture is still bound to the HD 3167 system. Similar global studies of multi-planet systems will tell how many share the peculiar properties of the HD 3167 system, which remains a target of choice for follow-up observations and simulations., This work has been carried out in the frame of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF). D. E. acknowledges financial support from the Swiss National Science Foundation for project 200021_200726. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (project SPICE DUNE, grant agreement No 947634; project FOUR ACES, grant agreement 724427; project SCORE, grant agreement No 851555). CHEOPS is an ESA mission in partnership with Switzerland with important contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom. The CHEOPS Consortium would like to gratefully acknowledge the support received by all the agencies, offices, universities, and industries involved. Their flexibility and willingness to explore new approaches were essential to the success of this mission. A. C. C. acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. S. G. S. acknowledges support from FCT through FCT contract nr. CEECIND/00826/2018 and POPH/FSE (EC). A. C. C. and T. G. W. acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. Y. A., M. J. H. and J. A. E. acknowledge the support of the Swiss National Fund under grant 200020_172746. We acknowledge support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grants ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, PGC2018-098153-B-C33, PGC2018-098153-B-C31, ESP2017-87676-C5-1-R, MDM-2017-0737 Unidad de Excelencia Maria de Maeztu-Centro de Astrobiología (INTA-CSIC), as well as the support of the Generalitat de Catalunya/CERCA programme. The MOC activities have been supported by the ESA contract No. 4000124370. S. C. C. B. acknowledges support from FCT through FCT contracts nr. IF/01312/2014/CP1215/CT0004. X. B., S. C., D. G., M. F. and J. L. acknowledge their role as ESA-appointed CHEOPS science team members. A. Br. was supported by the SNSA. This project was supported by the CNES. The Belgian participation to CHEOPS has been supported by the Belgian Federal Science Policy Office (BELSPO) in the framework of the PRODEX Program, and by the University of Liège through an ARC grant for Concerted Research Actions financed by the Wallonia-Brussels Federation. L. D. is an F. R. S.-FNRS Postdoctoral Researcher. This work was supported by FCT - Fundação para a Ciência e a Tecnologia through national funds and by FEDER through COMPETE2020 - Programa Operacional Competitividade e Internacionalizacão by these grants: UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020, PTDC/FIS-AST/32113/2017 & POCI-01-0145-FEDER-032113, PTDC/FIS-AST/28953/2017 & POCI-01-0145-FEDER-028953, PTDC/FIS-AST/28987/2017 & POCI-01-0145-FEDER-028987, O. D. S. D. is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. B. -O. D. acknowledges support from the Swiss National Science Foundation (PP00P2-190080). R. D. H. is funded by the UK Science and Technology Facilities Council (STFC)’s Ernest Rutherford Fellowship (grant number ST/V004735/1). M. F. and C. M. P. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19, 174/18). D. G. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 “Gaseous or rocky? Unveiling the nature of small worlds”. M. G. is an F.R.S.-FNRS Senior Research Associate. S. H. gratefully acknowledges CNES funding through the grant 837319. K. G. I. is the ESA CHEOPS Project Scientist and is responsible for the ESA CHEOPS Guest Observers Programme. She does not participate in, or contribute to, the definition of the Guaranteed Time Programme of the CHEOPS mission through which observations described in this paper have been taken, nor to any aspect of target selection for the programme. This work was granted access to the HPC resources of MesoPSL financed by the Region Île-de-France and the project Equip@Meso (reference ANR-10-EQPX-29-01) of the programme Investissements d’Avenir supervized by the Agence Nationale pour la Recherche. M. L. acknowledges support of the Swiss National Science Foundation under grant number PCEFP2_194576. PM acknowledges support from STFC research grant number ST/M001040/1. GSc, GPi, IPa, LBo, VNa and RRa acknowledge the funding support from Italian Space Agency (ASI) regulated by “Accordo ASI-INAF n. 2013-016-R.0 del 9 luglio 2013 e integrazione del 9 luglio 2015 CHEOPS Fasi A/B/C”. This work was also partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). I. R. I. acknowledges support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grant PGC2018-098153-B- C33, as well as the support of the Generalitat de Catalunya/CERCA programme. Gy. M. Sz. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, a PRODEX Institute Agreement between the ELTE Eötvös Loránd University and the European Space Agency (ESA-D/SCI-LE-2021-0025), the Lendület LP2018-7/2021 grant of the Hungarian Academy of Science and the support of the city of Szombathely. V.V.G. is an F.R.S-FNRS Research Associate. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Some of the observations in the paper made use of the High-Resolution Imaging instrument ‘Alopeke obtained under Gemini LLP Proposal Number: GN/S-2021A-LP-105. ‘Alopeke was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. Alopeke was mounted on the Gemini North (and/or South) telescope of the international Gemini Observatory, a program of NSF’s OIR Lab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea).

International audience

MELiSSA (Micro Ecological Life Support System Alternative) is developing bioregenerative Life Support technologies for long-term Space missions. The MELiSSA concept is conceived as a loop with several compartments, each one performing a specific function, providing all together edible material production, atmosphere regeneration and water recovery with a concomitant use of wastes, i.e., CO and organic wastes. Each one of the compartments is colonized with specific bacteria or higher plants depending on its specific function. The MELiSSA Pilot Plant is a facility designed for the terrestrial demonstration of this concept, hosting laboratory rats as a crew mock-up mimicking the respiration of humans. Currently, the MELiSSA Pilot Plant focus on the integration of three compartments: Compartment 3 (nitrifying packed-bed bioreactor based on the co-culture of immobilized Nitrosomonas europaea and Nitrobacter winogradsky), compartment 4a (an air-lift photobioreactor for the culture of the edible cyanobacteria Limnospira indica with concomitant oxygen production) and Compartment 5 (an animal isolator with rats as mock-up crew). The output from these tests shows a high robustness and reliability and the performance of oxygen producing and oxygen consuming compartments is successfully demonstrated under transitory and steady-state conditions. This contribution reports on the current state of development of the MELiSSA Pilot Plant Facility and the most recent results of the integration work., The MELiSSA Pilot Plant is funded from ESA contributions from Spain (main contributor), Belgium, France, Italy and Norway, under Frame Contract C4000109802/13/NL/CP. Co-funding from Ministerio de Ciencia e Innovación (RD 788/2020), Generalitat de Catalunya and Universitat Autònoma de Barcelona is also acknowledged.

International audience; Model-Based Systems Engineering (MBSE) is a development approach aiming to build correct-by-construction systems, provided the use of clear, unambiguous and complete models to describe them along the design process. The approach is supported by several engineering tools that automate the development steps, for example the production of code, documentation, test cases and more. TASTE [1] is pragmatic MBSE toolset supported by ESA that encapsulates several technologies to design a system (data modelling, architecture modelling, behaviour modelling/implementation), to automatically generate the binary application(s), and to validate it. One topic left open in TASTE is the formal verification of a system design with respect to specified properties. In this paper we describe our approach based on the IF model-checker [4] to enable the formal verification of properties on TASTE designs. The approach is currently under development in the ESA MoC4Space project.

The ocean mean dynamic topography (MDT) is the surface representation of the ocean circulation. The MDT may be determined by the ocean approach, which involves temporal averaging of numerical ocean circulation model information, or by the geodetic approach, wherein the MDT is derived using the ellipsoidal height of the mean sea surface (MSS), or mean sea level (MSL) minus the geoid as the geoid. The ellipsoidal height of the MSS might be estimated either by satellite or coastal tide gauges by connecting the tide gauge datum to the Earth-centred reference frame. In this article we present a novel approach to improve the coastal MDT, where the solution is based on both satellite altimetry and tide gauge data using new set of 302 tide gauges with ellipsoidal heights through the SONEL network. The approach was evaluated for the Northeast Atlantic coast where a dense network of GNSS-surveyed tide gauges is available. The typical misfit between tide gauge and satellite or oceanographic MDT was found to be around 9 cm. This misfit was found to be mainly due to small scale geoid errors. Similarly, we found, that a single tide gauge places only weak constraints on the coastal dynamic topography.

International audience; Meandered Waveguides are novel RF components which may play a disruptive role in phased array antennas. They permit to guarantee low propagation losses, comparable to the ones of conventional waveguides, combined with an increased freedom in defining their path, comparable with the one associated to flexible coaxial cables. In addition, meandered waveguides can provide a full control of the phase, which is fundamental to design Beam Forming Networks. Additive Manufacturing represents today the best technology to realize meandered waveguides with improvements in terms of cost, complexity, accommodation, and accuracy. In the paper in order to demonstrate the effectiveness of meandered waveguides possible exploitations in active arrays and discrete constrained lenses are proposed. © 2021 EurAAP.

International audience; Comets hold the key to the understanding of our Solar System, its formation and its evolution, and to the fundamental plasma processes at work both in it and beyond it. A comet nucleus emits gas as it is heated by the sunlight. The gas forms the coma, where it is ionised, becomes a plasma, and eventually interacts with the solar wind. Besides these neutral and ionised gases, the coma also contains dust grains, released from the comet nucleus. As a cometary atmosphere develops when the comet travels through the Solar System, large-scale structures, such as the plasma boundaries, develop and disappear, while at planets such large-scale structures are only accessible in their fully grown, quasi-steady state. In situ measurements at comets enable us to learn both how such large-scale structures are formed or reformed and how small-scale processes in the plasma affect the formation and properties of these large scale structures. Furthermore, a comet goes through a wide range of parameter regimes during its life cycle, where either collisional processes, involving neutrals and charged particles, or collisionless processes are at play, and might even compete in complicated transitional regimes. Thus a comet presents a unique opportunity to study this parameter space, from an asteroid-like to a Mars- and Venus-like interaction. The Rosetta mission and previous fast flybys of comets have together made many new discoveries, but the most important breakthroughs in the understanding of cometary plasmas are yet to come. The Comet Interceptor mission will provide a sample of multi-point measurements at a comet, setting the stage for a multi-spacecraft mission to accompany a comet on its journey through the Solar System. This White Paper, submitted in response to the European Space Agency’s Voyage 2050 call, reviews the present-day knowledge of cometary plasmas, discusses the many questions that remain unanswered, and outlines a multi-spacecraft European Space Agency mission to accompany a comet that will answer these questions by combining both multi-spacecraft observations and a rendezvous mission, and at the same time advance our understanding of fundamental plasma physics and its role in planetary systems.

This paper is an application oriented paper. It aims at demonstrating how model–based fault diagnosis and tolerant theories can be used to accommodate faults that may occur in spacecraft navigation units, i.e. at sensor level. The application support is the ESA’s In Orbit Assembly (IOA) project. This project is undertaken with GMV Space and Thales Alenia Space industries. The goal of the IOA mission is to assembly autonomously a telescope on a halo orbit around the Earth-Moon L2 point. The proposed solution is based on the observer structure of the (discrete time) subspace predictor and a nonlinear observer, for fault diagnosis. For fault tolerance, the solution relies on multi-sensor data fusion techniques based on the extended Kalman filter updated from the inverse-covariance form of the Kalman filter. The solution is evaluated under a realistic industrial environment.

The authors would like to thank the researchers and engineers who are not coauthors of this paper but who have taken part and have brought their contribution to the proposed missions to ESA successive calls: NEAT (M3), micro-NEAT (S1), and Theia (M4 and M5). An extensive list of supporters for the science objectives is given in [17]. We thank also Arianna Gallo for her contribution in our investigation of the shape of the MilkyWay dark matter halo and Krzysztof A. Rybicki who generated the plots from Fig. 14. We are grateful to the anonymous referee who helped to improve the quality of the paper with his/her remarks. Concerning the funding of our work, we would like to acknowledge the support of many agencies or programs. R.B. acknowledges support from NASA’s Virtual Planetary Laboratory lead team under cooperative agreements NNA13AA93A. A.C.M.C. acknowledges support from CFisUC strategic project (UID/FIS/04564/2019). F.C. acknowledges support by the Swiss National Science Foundation (SNSF) and by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (COSMICLENS: grant agreement No. 787886). M.F. received support from Polish National Science Centre (NCN) under Grant No. 2017/26/D/ST9/00591. M.F. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19, 174/18). D.H. thanks the Swedish National Space Agency (SNSA/Rymdstyrelsen) for their support. A.M. thanks the Portugese Fundac¸ ˜ao para a Ciˆencia e a Tecnologia (FCT) through the Strategic Programme UID/FIS/00099/2019 for CENTRA. P.S. acknowledges support from the Australian Research Council under grant FT190100814. L.W. acknowledges support from the Polish NCN grants: Harmonia No. 2018/06M/ST9/00311 and Daina No. 2017/27/L/ST9/03221. The OATo team acknowledges partial funding by the Italian Space Agency (ASI) under contracts 2014-025-R.1.2015 and 2018-24-HH.0, and by a grant from the Italian Ministry of Foreign Affairs and International Cooperation (ASTRA). A.C. and F.M. acknowledge support by the LabEx FOCUS ANR-11-LABX-0013. The work of C.J., X.L. and J.P. was supported by the Spanish Ministry of Science, Innovation and University (MICIU/FEDER, UE) through grants RTI2018-095076-B-C21, ESP2016-80079-C2-1-R, and the Institute of Cosmos Sciences University of Barcelona (ICCUB, Unidad de Excelencia ’Mar´ıa de Maeztu’) through grants MDM-2014-0369 and CEX2019-000918-M. A.K.-M., A.A., V.C., P.G., P.G., A.M.A., A.M., M.S. were supported by Fundac¸ ˜ao para a Ciˆencia e a Tecnologia, with grants reference UIDB/00099/ 2020 and SFRH/BSAB/142940/2018 (P.G. only). A.D. and L.O. also acknowledge partial support from the Italian Ministry of Education, University and Research (MIUR) under the Departments of Excellence grant L.232/2016, and from the INFN grant InDark. G.J.W. gratefully acknowledges support of an Emeritus Fellowship from The Leverhulme Trust. EV is supported by Spanish grant PGC2018-101950-B-100. This research has made use of NASA’s Astrophysics Data System Bibliographic Services. Open access funding provided by Istituto Nazionale di Astrofisica within the CRUI-CARE Agreement., Sky survey telescopes and powerful targeted telescopes play complementary roles in astronomy. In order to investigate the nature and characteristics of the motions of very faint objects, a flexibly-pointed instrument capable of high astrometric accuracy is an ideal complement to current astrometric surveys and a unique tool for precision astrophysics. Such a space-based mission will push the frontier of precision astrometry from evidence of Earth-mass habitable worlds around the nearest stars, to distant Milky Way objects, and out to the Local Group of galaxies. As we enter the era of the JamesWebb Space Telescope and the new ground-based, adaptive-optics-enabled giant telescopes, by obtaining these high precision measurements on key objects that Gaia could not reach, a mission that focuses on high precision astrometry science can consolidate our theoretical understanding of the local Universe, enable extrapolation of physical processes to remote redshifts, and derive a much more consistent picture of cosmological evolution and the likely fate of our cosmos. Already several missions have been proposed to address the science case of faint objects in motion using high precision astrometry missions: NEAT proposed for the ESA M3 opportunity, micro-NEAT for the S1 opportunity, and Theia for the M4 and M5 opportunities. Additional new mission configurations adapted with technological innovations could be envisioned to pursue accurate measurements of these extremely small motions. The goal of this White Paper is to address the fundamental science questions that are at stake when we focus on the motions of faint sky objects and to briefly review instrumentation and mission profiles., NASA’s Virtual Planetary Laboratory NNA13AA93A, CFisUC strategic project (UID/FIS/04564/2019), Swiss National Science Foundation (SNSF), European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (COSMICLENS: grant agreement No. 787886), Polish National Science Centre (NCN) under Grant No. 2017/26/D/ST9/00591, Swedish National Space Agency (DNR 65/19, 174/18), Swedish National Space Agency (SNSA/Rymdstyrelsen), Portugese Fundacão para a Ciência e a Tecnologia (FCT) through the Strategic Programme UID/FIS/00099/2019 for CENTRA, Australian Research Council under grant FT190100814, Polish NCN grants: Harmonia No. 2018/06M/ST9/00311 and Daina No. 2017/27/L/ST9/03221, Italian Space Agency (ASI) under contracts 2014-025-R.1.2015 and 2018-24-HH.0, Italian Ministry of Foreign Affairs and International Cooperation (ASTRA), LabEx FOCUS ANR-11-LABX-0013, Spanish Ministry of Science, Innovation and University (MICIU/FEDER, UE) through grants RTI2018-095076-B-C21, ESP2016-80079-C2-1-R, Institute of Cosmos Sciences University of Barcelona (ICCUB, Unidad de Excelencia ’Mar´ıa de Maeztu’) through grants MDM-2014-0369 and CEX2019-000918-M, Fundacão para a Ciência e a Tecnologia, with grants reference UIDB/00099/ 2020 and SFRH/BSAB/142940/2018 (P.G. only), Italian Ministry of Education, University and Research (MIUR) under the Departments of Excellence grant L.232/2016, and from the INFN grant InDark, Emeritus Fellowship from The Leverhulme Trust, Spanish grant PGC2018-101950-B-100, Istituto Nazionale di Astrofisica within the CRUI-CARE Agreement

International audience; Recently, convolutional neural networks have been successfully applied to lossy image compression. End-to-end optimized autoencoders, possibly variational, are able to dramatically outperform traditional transform coding schemes in terms of rate-distortion trade-off; however, this is at the cost of a higher computational complexity. An intensive training step on huge databases allows autoencoders to learn jointly the image representation and its probability distribution, possibly using a non-parametric density model or a hyperprior auxiliary autoencoder to eliminate the need for prior knowledge. However, in the context of on board satellite compression, time and memory complexities are submitted to strong constraints. The aim of this paper is to design a complexity-reduced variational autoencoder in order to meet these constraints while maintaining the performance. Apart from a network dimension reduction that systematically targets each parameter of the analysis and synthesis transforms, we propose a simplified entropy model that preserves the adaptability to the input image. Indeed, a statistical analysis performed on satellite images shows that the Laplacian distribution fits most features of their representation. A complex non parametric distribution fitting or a cumbersome hyperprior auxiliary autoencoder can thus be replaced by a simple parametric estimation. The proposed complexity-reduced autoencoder outperforms the Consultative Committee for Space Data Systems standard (CCSDS 122.0-B) while maintaining a competitive performance, in terms of rate-distortion trade-off, in comparison with the state-of-the-art learned image compression schemes.

This paper presents the modeling and analysis of the induced oscillations due to the Solar Array Drive Mechanism (SADM) on the pointing performances of a generic Earth observation spacecraft. First the SDT (Satellite Dynamics Toolbox) is used to obtain a Linear Parameter Varying model of the spacecraft fitted with a flexible solar panel parameterized according to its angular configuration. Then a detailed model of the SADM including the stepper motor and the gear box is included using the TITOP (Two-Input Two-Output Ports) approach. Such an approach allows to build the dynamic model of the structure just by assembling the sub-structure models. TITOP models consider the 6 d.o.f. (degrees of freedom) to take into account all the geometrical, kinematic and dynamic couplings required to capture the propagation of the perturbations inside the overall flexible structure. Moreover these models allows the user to evaluate the pointing errors on the 3 axes. Parametric robustness analysis tools are then used to isolate the worst harmonics of the various SADM imperfections and the solar array angular configuration from the pointing performance point of view.

International audience; A synthesis method for the design of large planar array antennas with phase-only control is here presented. The synthesis is based on the use of Zernike polynomials, as global basis function for the phase, to reduce the number of optimization variables with respect to the number of elements of the array. Invasive weed optimization (IWO) is applied to polynomial coefficientsand#x2019; optimization to circumvent non-linearity and local trapping issues typical of phase-only problems. The periodicity of the array factor is exploited to reduce the optimization to a Voronoi cell of the grating-lobesand#x2019; lattice and non-uniform meshing is introduced to best adapt the control stations to the beam shape requirements. The technique is applied to the design of shaped beams for continental coverage from geostationary satellites. IEEE

International audience; This paper outlines a complete methodology for designing a control system that reshapes the dynamic response of the flexible structure to robustly match the dynamics of a given adaptable reference model. The procedure was experimentally verified on a setup developed at the European Space Agency, consisting of a cantilevered flexible plate actuated by two shakers. Angular displacements at the free tip of the plate were measured with sub-microradian resolution using a laser autocollimator. Following a comprehensive system identification phase, mathematical models of the uncertain plant were extracted. The models reliably fit the experimental data and were used to synthesize a low order and high bandwidth structured Linear Parameter Varying controller. The controller was designed by taking into account the limits of achievable performance and the closed loop effectively constrained the flexible structure to behave like it was made out of an adaptable material. The robust stability and worst case performances were assessed by means of a structured singular value analysis and excellent agreement between theoretical predictions and experimental results was observed.

International audience; In recent years, neural networks have emerged as data-driven tools to solve problems which were previously addressed with model-based methods. In particular, image processing has been largely impacted by convolutional neural networks (CNNs). Recently, CNN-based auto-encoders have been successfully employed for lossy image compression [1,2,3,4]. These end-to-end optimized architectures are able to dramatically outperform traditional compression schemes in terms of rate-distortion trade-off. The auto-encoder is composed of an encoder and a decoder both learned from the data. The encoder is applied to the input data to produce a latent representation with minimum entropy after quantization. The latent representation, derived through several convolutional layers composed of filters and activation functions, is multi-channel (the output of a particular filter is called a channel or a feature) and non-linear. The representation is then quantized to produce a discrete-valued vector. A standard entropy coding method uses the entropy model inferred from the representation to losslessly compress this discrete-valued vector. A key element of these frameworks is the entropy model. In earlier works [1,2,3], the learned representation was assumed independent and identically distributed within each channel and the channels were assumed independent of each other, resulting in a fully-factorized entropy model. Moreover, a fixed entropy model was learned once, from the training set, preventing any adaptation to the input image during the operational phase. The variational auto-encoder proposed in [4] proposed to use a hyperprior auxiliary network. This network estimates the hyper-parameters of the representation distribution, for each input image. Thus, it does not require the assumption of a fully-factorized model which conflicts with the need for context modeling. This variational auto-encoder achieves compression performance close to the one of BPG (Better Portable Graphics) at the expense of a considerable increase in complexity.However, in the context of on-board compression, a trade-off between compression performance and complexity has to be considered to take into account the strong computational constraints. For this reason, the CCSDS (Consultative Committee for Space Data Systems) lossy compression standard has been designed as a highly simplified version of JPEG2000. This work follows the same logic, however in the context of learned image compression. The aim of this paper is to design a simplified version of the variational auto-encoder proposed in [4] in order to meet the on-board constraints in terms of complexity while preserving high performance in terms of rate-distortion. Apart from straightforward simplifications of the transform (e.g. reduction of the number of filters in the convolutional layers), we mainly propose a simplified entropy model that preserves the adaptability to the input image.A preliminary reduction of the number of filters reduces the complexity by 62% in terms of FLOPs with respect to [4]. It also reduces the number of learned parameters with a positive impact on the memory occupancy. The entropy model simplification exploits a statistical analysis of the learned representation for satellite images, also performed in [5] for natural images. This analysis reveals that most of the features are well fitted by centered Laplacian distributions. The complex hyperprior model based on a non-parametric distribution of [4] can thus be replaced by a simpler parametric centered Laplacian model. The problem then amounts to a classical and simple estimation of a single parameter referred to as the scale. Our simplified entropy models reduces the complexity of the variational auto-encoder coding part by 22% and outperforms the end-to-end model proposed in [1] for the high target rates.

In the context of future human spaceflight exploration missions, Rendezvous and Docking (RVD) activities are critical for the assembly and maintenance of cislunar structures. The scope of this research is to investigate the specifics of orbits of interest for RVD in the cislunar realm and to propose novel strategies to safely perform these kinds of operations. This paper focuses on far rendezvous approaches and passively safe drift trajectories in the Ephemeris model. The goal is to exhibit phasing orbit requirements to ensure a safe far approach. Ephemeris representations of Near Rectilinear Halo Orbits (NRHOs) were derived using multiple-shooting and adaptive receding-horizon targeting algorithms. Simulations showed significant drift and overlapping properties for phasing and target orbits of interest, motivating the search for safe natural drift trajectories and using impact prediction strategies.

This paper proposes a novel dynamic model of a Reaction Wheel Assembly (RWA) based on the Two-Input Two-Output Port framework, already presented by the authors. This method allows the user to study a complex system with a sub-structured approach: each sub-element transfers its dynamic content to the other sub-elements through local attachment points with any set of boundary conditions. An RWA is modelled with this approach and it is then used to study the impact of typical reaction wheel perturbations on a flexible satellite in order to analyze the micro-vibration content for a high accuracy pointing mission. This formulation reveals the impact of any structural design parameter and highlights the need of passive isolators to reduce the micro-vibration issues. The frequency analysis of the transfer between the disturbance sources and the line-of-sight (LOS) jitter highlights the role of the reaction wheel speed on the flexible modes migration and suggests which control strategies can be considered to mitigate the residual micro-vibration content in order to fulfil the mission performances.

This article presents and validates a general framework to build a linear dynamic Finite Element-based model of large flexible structures for integrated Control/Structure design. An extension of the Two-Input Two-Output Port (TITOP) approach is here developed. The authors had already proposed such framework for simple beam-like structures: each beam was considered as a TITOP sub-system that could be interconnected to another beam thanks to the ports. The present work studies bodies with multiple attaching points by allowing complex interconnections among several sub-structures in tree-like assembly. The TITOP approach is extended to generate NINOP (N-Input N-Output Port) models. A Matlab toolbox is developed integrating beam and bending plate elements. In particular a NINOP formulation of bending plates is proposed to solve analytic two-dimensional problems. The computation of NINOP models using the outputs of a MSC/Nastran modal analysis is also investigated in order to directly use the results provided by a commercial finite element software. The main advantage of this tool is to provide a model of a multibody system under the form of a block diagram with a minimal number of states. This model is easy to operate for preliminary design and control. An illustrative example highlights the potential of the proposed approach: the synthesis of the dynamical model of a spacecraft with two deployable and flexible solar arrays.

International audience; As the global space exploration community moves towards the exploration of the Moon and beyond, so mustthe preparation of crew operations. Given the distinct operational requirements of human lunar explorationscenarios compared to the on-going ISS operations, the study of human-robotic integrated operations (HRIO)is key in the endeavour of mankind’s return to the Moon and enabling a sustainable exploration strategy.Moving beyond qualitative performance assessments of HRIO, one particular issue for exploration destinationsare time-delay conditions, and therefore the step must be made towards quantifying performance in theseoperations such that both crew and system designs are prepared accordingly. Based on the pilot studypreviously presented in Hosseini et al. [1], the current paper presents a mission-driven experiment campaignset up to study human performance regarding the ESA-led HERACLES mission, a proposed sub-scaletele-operated demonstrator mission aiming to prepare international partners for human lunar missions. Atargeted geological site in a lunar crater is set up in an analogue environment at ESA allowing a roverto be tele-operated. The knowledge gap in HRIO is challenged in this study, since reaching this level ofhuman-robotic partnership requires an unprecedented understanding of the interaction between the humanand robotic system. The approach to fill this gap is to quantify objectively the HRIO performance forspaceflight applications, by studying human and robotic elements as two separate yet cooperating systems.16 participants were instructed to drive the rover through an obstacle course using a controller and camera asinterface to the rover. Three mission-driven time-delay conditions were applied to simulate different controlconfigurations, i.e. 3.5s, 0.5s, and 0s representing control from ground, cis-lunar space, and lunar surface,respectively, assuming the rover is driving on the lunar surface. The experiment is set up such that human performance metrics are acquired following a neuroergonomics approach, focusing on the cardiovascularactivity to infer participant’s mental workload, and ocular behaviour, to measure attentional abilities. Inparallel, robotic metrics are acquired through the hardware and software output of the rover. Studyinghuman and robotic data output recorded in parallel allows quantification of the level of mental workloadunder the delay conditions and the resulting effects on the HRIO performance. This approach is believed toadvance the level of detail and understanding of HRIO as known to date, subsequently identifying the keyelements to prepare astronauts for future missions

Multi-core, and Time and Space Partitionnong sys- tems are two emerging paradigms for architecting avionics systems. They impose new steps in the development process: capturing configuration attributes, analysing their correctness, or guaranteeing performance. In this context, model-based tech- niques provide a framework to design, analyse and synthesize these systems while automating much steps. In this paper, we report on a set of extenstions of TASTE to support multi-core and TSP systems. We first present the key architectural elements of these systems, and then detail how these have been support as part of the generation toolchain. We then present experiments realized on two case studies and two hardware targets, both provided with the XtratuM hypervisor.

Pointing performances are always more demanding for the scientific and observation Space missions of the future generation. A deep study of all the possible micro-vibration sources therefore results mandatory. This article presents several tools to analyze and control the micro-perturbations induced by a Solar Array Drive Mechanism (SADM) on a spacecraft. A first tool allows the user to build the dynamic model of a spacecraft composed of different flexible appendages attached to the main body by revolute joints. A second tool provides the SimScape model of a SADM that is interfaced with the spacecraft dynamics and allows analyzing the mission pointing performances. Time and frequency studies can be performed to deeply investigate pointing performances in presence of vibrations. An example that shows the interest of the proposed tools is provided. An observation spacecraft with two flexible solar arrays and an antenna is studied. The pointing metrics are computed for two complementary solutions to the micro-vibration issue: a microstepping technique for the SADM driver and a Fast Steering Mirror (FSM) for the active control of the Line of Sight (LOS).

Electromagnetic formation flight (EMFF) is a recent concept, aiming to control relative motions of formation flying satellites using magnetic interactions. Each satellite is equipped with a magnetic dipole. The formation degree of cooperation,depending on the ability of each spacecraft to control its dipole and its attitude, has a great impact on the methods used to perform the formation GNC. This paper describes results obtained in the case of semi-cooperative EMFF composed of a chaser and a target, in the field of navigation and guidance. Preliminary studies indicate that the target relative position and attitude can be determined while measuring the magnetic field at the chaser location, and the acceleration of this chaser. Focus is also made on the guidance for the whole formation orbit transfer, if only the chaser has thrust capacity: theory shows that geometrical configurations exist for which the formation is in an equilibrium state.

We report preliminary results on experimental investigations on condensation in the framework of the European Space Agency funded programme Enhanced Condensers in Microgravity (ENCOM-2) which aims at better understanding underlying phenomena during condensation. The first experiment is a study on condensation of HFE on external curvilinear surface of 15 mm height during reduced gravity experiments. It is found that the local minimum of the film thickness exists at the conjugation area of condensed film and the meniscus at the bottom of the fin; this leads to the local maximum of the heat transfer coefficient, which we also found moves towards the fin tip. The second experiment is a study of falling films hydrodynamics inside a vertical long pipe. In particular, characteristics of wavy falling films produced employing intermittent liquid feed are examined in order to assess wave effects on film condensation. Preliminary results suggest that intermittent feed simply divides the film in two autonomous regions with the wave feature of each one depending only on its flow rate. The processing of registered film thickness data can lead to the estimation of the transverse velocity profile in the film, which is mainly responsible for heat transfer during condensation. The third experiment looks at in-tube convective condensation at low mass fluxes (typical of Loop Heat Pipes and Capillary Pumped Loops) of n-pentane inside a 0.56 mm diameter channel. The results show that the mean heat transfer in the annular zone when it is elongated may be less than the mean heat transfer when it is shorter, due to the interface deformation involved by surface tension effect. When the length of this annular zone reaches a critical value, the interface becomes unstable, and a liquid bridge forms, involving the release of a bubble. The heat transfer due to the phase-change in this isolated bubble zone appears to be very small compared to the sensible heat transfer: the bubbles evolve and collapse in a highly subcooled liquid. The last experiment concerns in-tube condensation of R134a inside a square channel of 1.23 mm hydraulic diameter at mass fluxes of 135 kg m−2 s−1 and 390 kg m−2 s−1 for three different configurations: horizontal, vertical downflow and vertical upflow. For the calculated heat transfer coefficient it is found that gravity has no effect on condensation in downflow configurations at 390 kg m−2 s−1 and in upflow conditions at both values of mass velocity. The effect of gravity on the condensation heat transfer coefficient becomes noteworthy in downflow at mass velocity G = 135 kg m−2 s−1 and vapour quality lower than 0.6.

We present a CMOS image sensor dedicated to lightning detection and imaging. The detector has been designed to evaluate the potentiality of an on-chip lightning detection solution based on a smart sensor. This evaluation is performed in the frame of the predevelopment phase of the lightning detector that will be implemented in the Meteosat Third Generation Imager satellite for the European Space Agency. The lightning detection process is performed by a smart detector combining an in-pixel frame-to-frame difference comparison with an adjustable threshold and on-chip digital processing allowing an efficient localization of a faint lightning pulse on the entire large format array at a frequency of 1 kHz. A CMOS prototype sensor with a 256×256 pixel array and a 60 μm pixel pitch has been fabricated using a 0.35 μm 2P 5M technology and tested to validate the selected detection approach.

We present A CMOS image sensor dedicated to lightning detection and imaging. The detector has been designed for the pre-development phase of the lightning detector that will be implemented in Meteosat Third Generation Imager (MTG-I) satellite for European Space Agency (ESA). The lightning detection process (Patent applied) is performed by a smart detector combining on in-pixel frame to frame difference comparison with an adjustable threshold and onchip digital processing allowing an efficient localization of faint lightning pulse on the entire large format array at 1 kHz. A CMOS prototype sensor with a 256x256 pixel array and 60μm pixel pitch has been fabricated using a 0.35μm 2P 5M technology and tested to validate the selected detection approach. OCIS codes: (040.6070 ) Solid state detectors; (250.3140) Integrated optoelectronic circuits; (280.4788) Optical sensing and sensors; (110.2970) Image detection systems.

International audience; To qualify hardware for space flight, great care is taken to replicate the environment encountered in space. Emphasis is focused on presenting the hardware with the most extreme conditions it might encounter during its mission lifetime. The same care should be taken when regolith simulants are prepared to test space system performance. Indeed, the manner a granular material is prepared can have a very high influence on its mechanical properties and on the performance of the system interacting with it. Three regolith simulant preparation methods have been tested and are presented here (rain, pour, vibrate). They should enable researchers and hardware developers to test their prototypes in controlled and repeatable conditions. The pour and vibrate techniques are robust but only allow reaching a given relative density. The rain technique allows reaching a variety of relative densities but can be less robust if manually controlled.

A new trend in space systems is to move from big centralized satellites to smaller, but distributed systems: we call that formation flying, because the idea is to let several satellites achieve complex missions by combining the capabilities of payloads when they are distributed over several physical spacecrafts. For example, the Proba 3 mission will make use of two satellites to study the sun corona. The challenge is big, and will address all the questions that are raised when designing a distributed system: how to take decisions, how to detect faults, how to elect a master without any node knowing for sure the state of the complete system. To be ready to solve these issues, a rock-solid software development process must exist and be supported by tools, so that the system designer can concentrate on what is really new and challenging: the distributed algorithms. This chapter explains how the space sector in Europe tackled this problem of defining a proper development process, and what tools have been developed to deal with the specificities of embedded, heterogeneous systems. We first present the main characteristics of satellites systems and software, then the issues that are faced when developing them, what can be improved, and the concrete solutions that we developed in the scope of the TASTE project to ease the development, integration and validation of on-board software.

著者人数：49名, Accepted: 2010-05-11, 資料番号: SA1002596000

The TASTE tool-set results from spin-off studies of the ASSERT project, which started in 2004 with the objective to propose innovative and pragmatic solutions to develop real-time software. One of the primary targets was satellite flight software, but it appeared quickly that their characteristics were shared among various embedded systems. The solutions that we developed now comprise a process and several tools ; the development process is based on the idea that real-time, embedded systems are heterogeneous by nature and that a unique UML-like language was not helping neither their construction, nor their validation. Rather than inventing yet another "ultimate" language, TASTE makes the link between existing and mature technologies such as Simulink, SDL, ASN.1, C, Ada, and generates complete, homogeneous software-based systems that one can straightforwardly download and execute on a physical target. Our current prototype is moving toward a marketed product, and sequel studies are already in place to support, among others, FPGA systems.

In this chapter, we explain why the low gravity encountered on Mars or on the Moon and the low mass of the probes, landers and rovers that carry drilling devices limit classical drilling techniques. Novel boring solutions optimised in mass and power consumption are thus needed for space applications. Biologists have identified the wood wasp, an insect that is capable of "drilling" into wood to lay its eggs. A low mass and low power system, like an insect, capable of drilling into wood is of the highest interest for planetary drilling and terrestrial drilling alike. The general working principle of the wood wasp drill ("dual reciprocating drilling") will be exposed and the potential benefits of imitating the wood wasp for planetary drilling will be highlighted. Since the nature of wood is highly fibrous but the nature of extraterrestrial and terrestrial soils are not, it is necessary to adapt the wood wasp ovipositor to our target soils. A test bench to evaluate the influence of the different geometries and operational parameters was produced and is presented here. The dual reciprocating drilling experimental results obtained on this test bench are also highlighted. They should lead to a new and enhanced model and comprehension of dual-reciprocating-drilling.

In this paper, we detailed the formation/evolution of precipitates in alcoholic media containing Co(II+) and Li(+) species, together with the evolution of the composition and structure/texture of the resulting solid phases during the aging process at controlled constant temperature. While the end product is found to be well-crystallized HT-LiCoO(2), its formation is shown to result from a two-step process enlisting the initial fast precipitation of β-HCoO(2) and then its slow dissolution followed by recrystallization of the lithium-containing material. These results were obtained through combined X-ray diffraction, Raman and IR spectroscopy, elemental and oxidation-state analysis, and high-resolution transmission electron microscopy/selected-area electron diffraction observations. Depending on the cationic concentration, the size of the precipitated material can be controlled within the nanometric range. The electrochemical performances of these aged materials are slightly improved compared to those of the directly precipitated ones that we previously reported. The main limitation of these materials remains the presence of surface protons.

The micro-satellite DEMETER was launched on June 29, 2004 in a polar and circular orbit with an altitude of � 710 km. It is a CNES mission controlled from Toulouse in France. The main objective of DEMETER is to search and characterize ionospheric perturbations that can be associated with the seismic activity in order to better understand the generation mechanism of such perturbations. Its scientific payload allows us to measure waves in a broad frequency range and also some important plasma parameters (ion composition, electron density and temperature, energetic particles). This paper is a preliminary report of unusual observations recorded by DEMETER over seismic regions prior to earthquakes. The main purpose of the project is to perform a statistical analysis with many events in order to determine the necessary conditions to observe such seismo-electromagnetic effects. It is too early to perform such statistics but data recorded during selected events and shown here are useful since they may point out sensitive parameters which must be particularly surveyed in the statistical analysis. 2006 Elsevier Ltd. All rights reserved.

International audience; The wave complex ELISMA aboard the MARS-96 spacecraft was proposed and built by an international consortium involving nine institutes from seven European countries. ELISMA is the main dedicated wave instrumentation of the mission, although the on-board magnetometer part of the MAREMF experiment will carry out other specific and complementary measurements, and the RLK radar will record passive HF waves. Several antenna sets dispatched on different booms and wave analyzers provide a frequency range from a fraction of Hz to almost 2 MHz for the electric field and up to 2 kHz for the magnetic field. After the pioneer investigation of natural waves in the Martian environment made by the PHOBOS spacecraft, this mission offers the first opportunity of carrying out precise measurements within a much wider frequency range, in a shorter time and with better frequency resolution, a deeper exploration down to the ionospheric level and over a much longer time in orbit, thus making it possible to study latitudinal, diurnal and seasonal variations. In addition to measuring natural waves and plasma instabilities, ELISMA will carry out precise measurements of thermal plasma using active modes of several sensors and antennae. The absolute electron density and thermal energy will be obtained using the mutual impedance technique and high-frequency antennae; the Langmuir probes will record complementary measurements of abrupt variations in these quantities. They will monitor the spacecraft potential and carry out a survey of the UV solar flux. This paper introduces the consortium participants, describes successively the different parts of the ELISMA experimentation and their dedicated scientific objectives, and outline certain aspects concerning the flight operations and data handling.

International audience; We present the first results of a sensitive (K ≈ 17 mag) near IR (JHK) imaging survey of a complete IRAS selected sample of Young Stellar Objects (YSO’s) belonging to a Giant Molecular Cloud (GMC) located in the Vela Molecular Ridge (VMR). The same objects have also been observed at λ = 1.3mm. We provide identifications (i.e. NIR counterparts) and detailed spectral energy distributions (SED’s) for ten newly identified Class I objects. The envelope masses are consistent with central masses derivable from the observed luminosities. Detected multiplicity indicates that intermediate mass star formation might not represent an individual and isolated phenomenon.