Corrélateurs du Futur

Accepté Revue de l'électricité et de l'électronique (REE) 2012Le Laboratoire d'Astrophysique de Bordeaux (LAB) a contribué techniquement au projet ALMA à travers la conception de deux sous-systèmes de l'interféromètre : les convertisseurs analogiques numériques (CAN) et les bancs de filtres numériques. Les spécifications de ces deux sous-systèmes ont une incidence directe sur l'architecture du corrélateur, particulièrement les filtres numériques qui sont à l'origine des nombreux modes d'observation proposés et des performances spectrales de l'instrument. Par ses performances et sa prochaine ouverture à la communauté scientifique, le corrélateur ALMA est un corrélateur du futur, cependant des technologies plus avancées que celles mises en oeuvre pour sa conception sont d'ores et déjà disponibles. De nouveaux développements sont donc en cours au LAB afin de préparer la prochaine génération d'instrument

Radar Sounding Investigations of the Martian Subsurface by the 2018 ExoMars-C Rover

International audienceThe WISDOM (Water Ice Subsurface Deposit Observation on Mars) Ground Penetrating Radar will fly on the ESA-NASA 2018 ExoMars-C mission, which combines the science payload of the original ESA ExoMars Rover with the robotic arm and sample cache of NASA's Max-C Rover into a single rover, whose samples will ult imately be retrieved by a future Mars Sample Return mission. WISDOM was designed to investigate the nearsubsurface down to a depth of ~2-3 m, commensurate with the sampling capabilit ies of the rover's drill. The information provided by WISDOM will assist in understanding the large-scale geology and history of the landing site, as well as selecting the most appropriate locations where to drill and collect sub surface samples for further analysis. Here we review the real-world performance of the instrument as experimentally observed in various field test environments

Results from the First Field Tests of the WISDOM GPR (2018 ExoMars Mission)

International audienceIntroduction: The WISDOM (Water Ice Subsur- face Deposit Observation on Mars) Ground Penetrating Radar (GPR) is one of the instruments that have been selected as part of the Pasteur payload of ESA’s 2018 ExoMars Rover mission[1]. The Pasteur payload actu- ally consists of two different sets of instruments: the Panoramic Instruments, which include a wide angle camera and the WISDOM radar, that will be used to perform large-scale scientific investigations of the landing site and the Analytical Laboratory Instruments that will analyze the core samples obtained by the sub- surface drill. WISDOM will help identify the location of sedimentary layers, where organic molecules are the most likely to be found and well-preserved. WISDOM has been designed to investigate the near subsurface environment down to a depth of ~2-3 m with a vertical resolution of a few centimeters [2]. WISDOM is a step frequency radar operating over a wide frequency band between 0.5 and 3 GHz. Particular attention was paid to the design of the antenna system, which needs to be able to conduct polarimetric measurements over the whole bandwidth without significant distortion [3]

The SuperCam Remote Sensing Instrument Suite for Mars 2020

International audienceThe Mars 2020 rover, essentially a structural twin of MSL, is being built to a) characterize the geology and history of a new landing site on Mars, b) find and characterize ancient habitable environments, c) cache samples for eventual return to Earth, and d) demonstrate in-situ production of oxygen needed for human exploration. Remote-sensing instrumentation is needed to support the first three of these goals [1]. The SuperCam instrument meets these needs with a range of instrumentation including the highest-resolution remote imaging on the rover, two different techniques for determining mineralogy , and one technique to provide elemental compositions. All of these techniques are co-boresighted, providing rapid comprehensive characterization. In addition, for targets within 7 meters of the rover the laser shock waves brush away the dust, providing cleaner surfaces for analysis. SuperCam will use an advanced version of the AEGIS robotic target selection software

La RadioAstronomie pour Tous

Le Laboratoire d'Astrophysique de Bordeaux (anciennement Observatoire de Bordeaux) est doté sur son site d'un radiotélescope Würzburg de 7.5m de diamètre, utilisé dans le domaine de la radioastronomie. Cet instrument, ancien radar de la deuxième guerre mondiale, a été utilisé à l'Observatoire de Bordeaux à partir des années 1960 pour des observations solaires routinières à la fréquence de 930MHz. Abandonné dans les années 1990, le radiotélescope est maintenant rénové et ouvert au grand public depuis Mai 2011. Un système électronique nouveau et un programme informatique développé en Python permettent de pointer l'antenne, de détecter et d'analyser le signal radio émis par les sources astronomiques. Une interface Web réalisée en PHP permet de faire le lien entre l'instrument et l'utilisateur sur internet. Chaque utilisateur peut réserver du temps d'observation pour mesurer l'émission radioélectrique de zones ou de sources à la fréquence de l'hydrogène atomique HI, soit 1420MHz. Un manuel d'utilisation est mis en ligne afin d'aider les utilisateurs à utiliser l'antenne et exploiter leurs données en utilisant le logiciel GILDAS. Un exemple didactique de cartographie de la galaxie est même mis à disposition pour permettre à des enseignants de réaliser un projet pédagogique. L'utilisation de ce radiotélescope permet ainsi de découvrir la radioastronomie, en observant depuis chez soi ou depuis une classe, d'appréhender des notions fondamentales comme les repères, les échelles, l'effet Doppler, la spectroscopie et acquérir les qualités nécessaires au traitement et à l'analyse d'une observation (rigueur, précision, esprit critique, bases mathématiques, rédaction). C'est aussi un moyen de découvrir les technologies et savoirs utilisés dans la Recherche

Initial Field and Calibration Tests of the WISDOM GPR for the 2018 ExoMars Mission

The WISDOM (Water Ice Subsurface Deposit Observation on Mars) Ground Penetrating Radar has been selected for inclusion in the payload of the rover for the ESA ExoMars mission (2018) [1]. WISDOM will remotely characterize the shallow subsurface of Mars, providing information essential to understanding the local geological context and the identification of the best locations for obtaining subsurface cores with the rover’s onboard drill.The requirements for the instrument’s performance are driven by the objectives of the mission (a vertical resolution of a few cm and a nominal penetration depth of ~3 m). A series of initial field tests and calibrations have been initiated in simple environments to validate the performance of the instrument. Preliminary results show that WISDOM’s calibrated data should provide reliable contextual and quantitative information about the nature of the Martian shallow subsurface. The instrument’s depth of sounding, vertical resolution and accuracy are consistent with its expected performance

A 4 GHz digital receiver using the Uniboard platform

The Uniboard is a general purpose board, developed as a part of the Radionet FP7 program, that hosts 8 Altera StratixIV FPGAs interconnected by high speed links. It can be used standalone or as a part of a more complex system. The Digital receiver application uses a single Uniboard to implement a flexible packetization of a wideband signal in the frequency domain. It accepts a 4 GHz (8 GS/s) input bandwidth and provides up to 64 output bands. The bandwidth and position of each output band can be independently adjusted. The input signal is first analyzed by a polyphase filterbank, that splits the input band into 32 sub-bands with a bandwidth of 190 MHz and a spacing of 128 MHz. The overlap among adjacent bands allows the positioning of the output bands without dead regions. This filterbank is followed by an array of digitally defined downconverters, each one composed of a mixer/LO and a variable decimation filter. The filter band can be adjusted in binary steps from 1 to 128 MHz. Using tap recirculation, the filter shape remains constant over this whole range, with about 60 dB of stopband rejection and 90% usable passband. The output bands are packetized according to the VDIF VLBI standard, over eight 10G Ethernet links. Further processing can be done either on board, or in a cluster of conventional PCs. In addition, high speed ADC are in-house developed (ASIC 65nm CMOS STmicroelectronics) to feed the Uniboard card with 8GS/s, 4GHz BW, 3bits samples

The WISDOM Radar onboard the Rover of the ExoMars mission

International audienceThe most fundamental and basic aspect of the geologic characterization of any environment is understanding its stratigraphy and structure - which provides invaluable insights into its origin, the processes and events by which it evolved, and (through the examination of superpositional and cross-cutting relationships) their relative timing. The WISDOM GPR onboard the Rover of the ESA ExoMars mission (2016) has the ability to investigate and characterize the nature of the subsurface remotely, providing high-resolution (several cm-scale) data on subsurface stratigraphy, structure, and the magnitude and scale of spatial heterogeneity, to depths in excess of 3 m. Unlike traditional imaging systems or spectrometers, which are limited to characterization of the visible surface, WISDOM can access what lies beneath - providing an understanding of the 3-dimensional geologic context of the landing site along the Rover path. WISDOM will address a variety of high-priority scientific objectives: (1) Understand the geology and geologic evolution of the landing site, including local lithology, stratigraphy and structure. (2) Characterize the 3-D electromagnetic properties of the Landing Site - including the scale and magnitude of spatial heterogeneity - for comparison with those measured at larger scales by MARSIS, SHARAD and any future orbital radars. (3) Understand the local distribution and state of shallow subsurface H2O and other volatiles, including the potential presence of segregated ground ice (as ice lenses and wedges), the persistent or transient occurrence of liquid water/brine, and deposits of methane hydrate and (4) identify the most promising locations for drilling that combine targets of high scientific interest. In addition to these objectives, there are also clear scientific and operational benefits when WISDOM is operated in concert with the rover's drill and its associated analytical instruments, which will determine the compositional and physical properties of retrieved core samples, thus helping to constrain and provide 'ground truth' for the interpretation of the WISDOM data. The instrument design and its specificities will be briefly presented. Results of numerical simulations will illustrate its expected performances in realistic Martian environments. Eventually experimental data collected in various environments on Earth will point out the potential of WISDO

Les Programmes R&D du Laboratoire d'Astrophysique de Bordeaux

Les domaines astrophysiques bénéficiant de la R&D * Formation stellaire : la haute résolution spectrale offerte par l'instrument HIFI du HSO permet des progrès considérables en ce qui concerne la caractérisation des premières phases de formation stellaire, avec l'étude de la structure chimique, physique et dynamique des étoiles massives et de type solaire, mais aussi des galaxies. De même, ALMA sera un instrument unique qui permettra de produire des images détaillées de galaxies en formation, d'étoiles, de planètes, et de nuages interstellaires contenant des composés chimiques nécessaires au développement de la vie. * Atmosphères et surfaces planétaires: le HSO est également un instrument clé pour progresser dans la compréhension des atmosphères planétaires (composition, évolution), tout comme le sera ALMA. S'agissant des surfaces planétaires, le rover de la mission Mars Science Laboratory (MSL) permettra d'évaluer si Mars est ou fût un environnement habitable. Cette mission partira fin 2011 et sera suivie à l'horizon 2020 par un rover de l'ESA dans le cadre du programme EXOMARS. * Systèmes de référence et noyaux actifs de galaxies : la radio-interférométrie à très longue base (VLBI) permet de construire des systèmes de référence ultra-précis basés sur les positions de sources extragalactiques compactes ainsi que de cartographier ces mêmes sources avec une résolution angulaire inégalée. La plateforme UNIBOARD construite dans le cadre du projet FP7-RadioNet servira de base au corrélateur VLBI européen de prochaine génération en projet à JIVE (Joint Institute for VLBI in Europe)

WISDOM A GPR FOR THE EXOMARS ROVER MISSION

The WISDOM GPR has been designed and selected for the ExoMars rover mission to investigate the near subsurface. It will help addressing important questions about the nature and history of the landing site and selecting location for drilling