Science objectives and performances of NOMAD, a spectrometer suite for the ExoMars TGO mission

The NOMAD spectrometer suite on the ExoMars Trace Gas Orbiter will map the composition and distribution of Mars atmospheric trace species in unprecedented detail, fulfilling many of the scientific objectives of the joint ESA-Roscosmos ExoMars Trace Gas Orbiter mission. The instrument is a combination of three channels, covering a spectral range from the UV to the IR, and can perform solar occultation, nadir and limb observations. In this paper, we present the science objectives of the instrument and how these objectives have influenced the design of the channels. We also discuss the expected performance of the instrument in terms of coverage and detection sensitivity.

The Martian Gas-Analytic Package for the Landing Platform Experiments of the ExoMars 2018

The paper describes the architecture of the Martian Gas Analytic Package, which is proposed for the Russian ExoMars Lander 2018.

Diseño preliminar térmico y estructural del instrumento NOMAD de ExoMars

El vehículo espacial ExoMarsOrbiter, llamado Exomars Trace Gas Orbiter (EMTGO), se encuadra en una misión de la ESA/NASA, contribuyendo a las ambiciones europeas de misiones de exploración futura, según lo establecido en la declaración Aurora. Los objetivos del programa ExoMars dan continuidad a los esfuerzos de cooperación con la NASA para enviar una misión de retorno de una muestra de Marte en las siguientes décadas. Están prevista s dos misiones dentro del programa ExoMars, una para 2016 y otra para 2018. NOMAD (solar occultation in the infra red and Nadir and Occultation for MArs Discovery) es un espectrómetro de alta resolución en el infrarrojo - visible - ultravioleta, observando en las franjas de 0.2 - 0.65 y 2.3 - 4.2 μm, para la inspección de la atmósfera de Marte. Dispone de tres canales (LNO, SO y UVIS) que operarán según tres modos distintos (ocultación solar, limbo y nadir). NOMAD es un instrumento con una masa de 29.9 kg que está montado sobre la bandeja superior exterior, en la cara fría del vehículo, y debe estar fuertemente desacoplado del mismo desde un punto de vista térmico (con una conductancia total máxima de 0.02 W/K). Este desacoplamiento dificulta el diseño estructural de la unión con el vehículo. El diseño térmico debe estar capacitado además para evacuar el calor disipado internamente y las cargas exteriores, utilizando únicamente métodos de control térmico pasivos. Un requisito térmico adicional es el que impone e l espectrómetro del canal LNO, que es una caja interior a NOMAD que debe ser enfriada a - 100º C. Con el objeto de cumplir estos requisitos, se disponen dos radiadores: un radiador ‘general’ para mantener al conjunto del instrumento a una temperatura semejante a la ambiente terrestre, y un radiador multietapa en “V” para enfriar la sección del LNO a - 100º C. Éste último consiste en 4 etapas con placas delgadas, que disponen de una combinación de regiones de alta emisividad y otras de alta reflectividad, para evacuar el calor entre etapas. Además, se ha de alcanzar un compromiso entre la rigidez del radiador y la masa del mismo para disminuir la masa del radiador, las placas delgadas deben ser rigidizadas estructuralmente. Tanto su diseño térmico como el estructural representan un reto tecnológico, debido a su escasa presencia en misiones anteriores. El modelo geométrico y los modelos matemáticos térmico s y estructural es se han construido siguiendo los estándares de la ESA. Esto es, la metodología utilizada ha sido la de efectuar primero un diseño conceptual preliminar, para posteriormente desarrollar un modelo térmico y otro estructural a nivel instrumento, con el software ESATAN y NASTRAN, ambos indicados por la ESA. Los resultados muestran la viabilidad de NOMAD desde un punto de vista térmico y estructural.

A Bacterial Enrichment Study and Overview of the Extractable Lipids from Paleosols in the Dry Valleys, Antarctica: Implications for Future Mars Reconnaissance

The Dry Valleys of Antarctica are one of the coldest and driest environments on Earth with paleosols in selected areas that date to the emplacement of tills by warm-based ice during the Early Miocene. Cited as an analogue to the martian surface, the ability of the Antarctic environment to support microbial life-forms is a matter of special interest, particularly with the upcoming NASA/ESA 2018 ExoMars mission. Lipid biomarkers were extracted and analyzed by gas chromatography-mass spectrometry to assess sources of organic carbon and evaluate the contribution of microbial species to the organic matter of the paleosols. Paleosol samples from the ice-free Dry Valleys were also subsampled and cultivated in a growth medium from which DNA was extracted with the explicit purpose of the positive identification of bacteria. Several species of bacteria were grown in solution and the genus identified. A similar match of the data to sequenced DNA showed that Alphaproteobacteria, Gamma-proteobacteria, Bacteriodetes, and Actinobacteridae species were cultivated. The results confirm the presence of bacteria within some paleosols, but no assumptions have been made with regard to in situ activity at present. These results underscore the need not only to further investigate Dry Valley cryosols but also to develop reconnaissance strategies to determine whether such likely Earth-like environments on the Red Planet also contain life.

Applications of electrified dust and dust devil electrodynamics to Martian atmospheric electricity

Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kVm-1 to 100 kVm-1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m-1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)-MicroARES (Atmospheric Radiation and Electricity Sensor) instrumentation to Mars in 2016 for the first in situ measurements.

The SCITEAS experiment: Optical characterizations of sublimating icy planetary analogues

We have designed and built a laboratory facility to investigate the spectro-photometric and morphologic properties of different types of ice-bearing planetary surface analogs and follow their evolution upon exposure to a low pressure and low temperature environment. The results obtained with this experiment are used to verify and improve our interpretations of current optical remote-sensing datasets. They also provide valuable information for the development and operation of future optical instruments. The Simulation Chamber for Imaging the Temporal Evolution of Analogue Samples (SCITEAS) is a small thermal vacuum chamber equipped with a variety of ports and feedthroughs that permit both in-situ and remote characterizations as well as interacting with the sample. A large quartz window located directly above the sample is used to observe its surface from outside with a set of visible and near-infrared cameras. The sample holder can be easily and quickly inserted and removed from the chamber and is compatible with the other measurement facilities of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern. We report here on the results of two of the first experiments performed in the SCITEAS chamber. In the first experiment, fine-grained water ice mixed with dark organic and mineral matter was left to sublime in vacuum and at low temperature, simulating the evolution of the surface of a comet nucleus approaching the Sun. We observed and characterized the formation and evolution of a crust of refractory organic and mineral matter at the surface of the sample and linked the evolution of its structure and texture to its spectro-photometric properties. In the second experiment, a frozen soil was prepared by freezing a mixture of smectite mineral and water. The sample was then left to sublime for 6 h to simulate the loss of volatiles from icy soil at high latitudes on Mars. Colour images were produced using the definitions of the filters foreseen for the CaSSIS imager of the Exomars/TGO mission in order to prepare future science operations.

Solderjet bumping technique used to manufacture a compact and robust green solid-state laser

Solder-joining using metallic solder alloys is an alternative to adhesive bonding. Laser-based soldering processes are especially well suited for the joining of optical components made of fragile and brittle materials such as glasses, ceramics and optical crystals due to a localized and minimized input of thermal energy. The Solderjet Bumping technique is used to assemble a miniaturized laser resonator in order to obtain higher robustness, wider thermal conductivity performance, higher vacuum and radiation compatibility, and better heat and long term stability compared with identical glued devices. The resulting assembled compact and robust green diode-pumped solid-state laser is part of the future Raman Laser Spectrometer designed for the Exomars European Space Agency (ESA) space mission 2018.