Europe has just launched the construction of the largest ground-based telescope: the ELT. In operation by 2024, this 40m giant willopen a new era in astronomy. It will answer fundamental questions from the search and characterization of extra-solar planets (the ultimate goal being the exo-earth imaging) to the formation and evolution of the first galaxies of the Universe. In order to achieve these ambitious objectives, telescopes have to correct aberrations introduced by the atmosphere in real time; this is the role of Adaptive Optics [AO]. Wavefront sensors [WFSs] are at the heart of this state-of-the-art instrumentation technique and their characteristics are the key to achieving the ultimate performance of ground-based telescopes. To enable the characterization of exo-planets or the study of distant galaxies, WFS performance gains of an order of magnitude on the accuracy, the measurement speed and the robustness are required. This is the goal set by the WOLF project. For this, we will rely on a new family of WFS - Fourier filtered Wavefront Sensors [FFWFS]. Our group (ONERA and LAM) has recently proposed a rigorous mathematical formalism which allows the description and study both qualitatively and quantitatively of the quite remarkable properties of these sensors. The WOLF project will use this formalism to design innovative FFWFS optimized according to the conditions of use (sensitivity, ultimate performance, linearity, robustness ...). WOLF must therefore provide a set of new sensors, fully tested, validated and ready to be implemented on the future instruments of the ELT. To achieve these ambitious goals, the work plan was divided into three stages of increasing complexity - each representing a key milestone of the project: 1. Theoretical and conceptual developments based on comprehensive simulation tools. This first step will allow us to propose the concepts of innovative FFWFS and to quantify their theoretical performance; 2. An implementation of prototypes which will then be validated in laboratory using a unique experimental bench developed at LAM. This step will enable the performance of the sensors to be established as well as the calibration processes and the operating modes to be developed; 3. On-sky validation using the 4-m William Herschel Telescope [WHT] and its CANARY AO platform. The FFWFS prototypes will be tested under the most realistic conditions possible. This step, although entailing risks inherent to any demonstration on an astronomical telescope, has a huge potential gain since it allows the WFS concepts to reach a level of maturity compatible with a future use of these sensors into operational astronomical instruments. The team involved in WOLF brings together European experts in the field around 3 French institutes - ONERA, LAM (Marseille Observatory) and LESIA (Paris Observatory) - and 3 associated European partners: INAF Arcetri, INAF Padova and University of Durham. The project will benefit from ONERA and LAM simulation tools and infrastructure for laboratory testing and a privileged access to WHT through LESIA and the University of Durham. In conclusion, the WOLF project benefits from a unique synergy between European laboratories. It fits perfectly into the national strategy of instrumental development related to the ELT. It will be the ideal complement to the design studies of new AO systems and will push them to their ultimate limits in terms of performance and robustness. WOLF will be a key step in the development of the next generation of OA systems for the next 20 years that will allow to obtain major breakthroughs in the astrophysics.

The New Horizons 2015 encounter with the Pluto system unveiled a remarkably active world, with a highly variegated surface displaying glaciers and dunes made of volatile N2, CH4, CO ices, and a chemically-rich atmosphere with extensive haze layers. These exotic, and sometimes enigmatic observations raised new fundamental questions on the evolution of the atmosphere and surface of Pluto and of similar worlds (cold objects with tenuous condensable atmospheres, e.g. Triton and other Trans-Neptunian objects) and call upon modeling efforts to complete their analysis and understand the associated mechanisms at play. In our SHERPAS project, we aim at using Pluto as a natural laboratory to study planetary climate physics and dynamics. In particular, our objectives are to understand: (1) What controls the thermal profile of Pluto’s atmosphere, in particular the unexpected 40K cooling above the stratosphere and the 3km-deep cold layer above the surface. Is it the organic haze? Does hydrocarbons condensation in the atmosphere plays a role? we recently acquired JWST observations of Pluto, which will provide us with clues regarding the radiative impact of the organic haze. We will also explore the thermal profile of Triton’s atmosphere, which remains largely unexplained. (2) What processes trigger the formation of atmospheric waves and observed haze layers. Are the waves dominated by a topographic forcing or by the diurnal sublimation and condensation (“breathing”) of nitrogen ice deposits? How do these waves affect the state of such tenuous atmospheres (e.g. temperatures and winds) ? (3) What surface-atmosphere interactions form the icy periodic bedforms observed at Pluto’s surface. Is it rather sublimation or condensation that dominates the formation of these structure? How do they compare to other similar ones in the solar system, especially on Earth and Mars? To achieve these goals, we will develop a new-generation global climate model, capable of simulating the atmosphere and surface of Pluto, Triton, and even other trans-Neptunian objects. This model will contain an ultra-parallelizable dynamic core, making it possible to speed up calculations by a factor of 200 compared to what is achieved today with the current Pluto model, which is crucial for simulating a Plutonian year (248 years). We will develop a complete radiative transfer scheme for Pluto and Triton, the microphysics of organic haze and clouds, the impact of micro-climates on slopes, and that of atmospheric waves on winds. The atmospheric model will also be coupled with a surface model to simulate the paleoclimates of Pluto and Triton over more than 100 million years. Finally, an exosphere model will be added to simulate the possible local and non-global atmospheres of Eris and Makemake when these objects approach their perihelion. These developments will directly and strongly benefit the scientific investigations of this project, and also beyond. In particular, the Generic model, simulating the climate of exoplanets, will be able to benefit from all the schemes that we will develop (microphysics of haze and hydrocarbons, radiative transfer, subgrid-scale slopes and wave scheme, paleoclimate model). We will combine the expertise of 3 laboratories (LESIA, LMD and LPG), and will compare our model results with available observations to interpret them. We will conduct comparative planetology studies, in particular between Pluto, Earth and Mars for surface ice structures, between Pluto, Triton and Mars for gravity waves, and between Pluto, Triton, Titan and early Earth for the radiative impact of the haze. These comparisons will allow us to assess the universality or uniqueness of the phenomena encountered on Pluto. The SHERPAS project will recruit: 1 two-year postdoctoral researcher at LESIA; 1 PhD at LPG, 1 research engineer at LMD.

Since the discovery in the 1990's of the first planet orbiting a distant star, the detection of hundreds of exo-planets have been confirmed. After these discoveries, the key issues are now to characterise these planetary systems and to understand how they forme and evolve. Another important issue is whether an "habitable'' zone for planets around stars exists or not. To answer these questions, it is mandatory to get a precise description of the main driver of the system: the star. The success of space missions based on stellar photometric observations, such as MOST, CoRoT and Kepler now makes possible the detailed study of the properties of stars. The presence of the PLATO and ECHO missions in the selection process for the ESA M3 mission will magnify the new possibilities opened by already launched missions. The first seismic analyses and interpretations performed in the past four years have demonstrated the potential of asteroseismology to investigate the physics of stars. In addition, the ultra-precise photometry provided by the aforementioned space experiments also allows new possibilities of investigation, for example in terms of magnetic activity through the study of the microvariability of the stars. The present proposal aims at precisely characterising the stars in order to determine their influence on their possible planetary system. As the determination of the size and mass of an exo-planet depends on that of the star, one of our goals is to obtain precise stellar mass and radius measurements. Physical conditions at the surface of a planet will depend on the radiative and magnetic interactions between the star and the planets: we therefore also aim at precise measurements of the star's luminosity and at a quantification of the star's magnetic activity and of their driving on the planetary system. Additional information such as the chemical characteristics of the star (helium and other element abundances), having a link with the process of planet formation, will be derived. The availability of space-borne observations providing photometric data of an unprecedented intrinsic quality (duration, precision, stability), coupled with the power of asteroseismic analysis now makes these objectives possible. Stellar modelling is the underlying tool for the interpretation of the results. The precision reached by observations calls for up-to-date stellar modelling that includes dynamical mechanisms such as transport of angular momentum by meridional circulation and internal gravity waves. As one of the main issues is the existence and extent of habitable zones around stars, our solar system will be used as a benchmark for the star-planet relation. More precisely, we will focus on the couple Sun-Mars, as this planet is thought to have lost its atmosphere because of the wind emitted by the young Sun. This will allow us to answer the question about the past of Mars and its possible habitability at the beginning of its history in the frame of the validation of our models in terms of magnetic activity. To sum up, we aim at providing the characteristics of the stellar radiative and magnetic driving on planets to experts in planetology. The underlying approach to our scientific program is the exploitation of stellar modelling tools combined with seismic observations of the best possible quality, in order to characterise the most precisely possible a star, and to be able to infer in a reliable manner the physical driving of the star in the star-planet relations.

Cepheids are the backbone of the extragalactic distance ladder. For instance, the discovery of the accelerated expansion of the Universe (Nobel Prize 2011) is largely based on the Cepheids. However, there is currently a 5 sigma tension between the acceleration rate of the universe derived from the cosmic microwave background and the one derived from the distance ladders. If confirmed, the tension would mean that the lambda-CDM model of the universe need refinements. The goal of this ANR project is to open a new route toward Ho using the Baade-Wesselink method (BW) of Cepheid distance determination. The concept of the method is simple: The variation of the angular diameter (from surface brightness-color relations or interferometry) is compared to the variation of the linear diameter (from the integration of the radial velocity). The distance of the Cepheid is then obtained by a simple division of the linear and angular amplitudes. The major weakness of the BW technique is that it uses a numerical factor to convert disk-integrated radial velocities into photospheric velocities, the projection-factor. This factor, whose value is typically around 1.3, characterises simultaneously the spherical geometry of the pulsating star, the limb darkening, and the difference in velocity between the photosphere and the line-forming regions ! Due to this intrinsic complexity, the p-factor is currently uncertain to ~7%, and accounts for almost all the systematic uncertainties of the Galactic Cepheid BW distances. Using a novel generation of interferometer, dedicated photometric and spectroscopic observations as well as state-of-the-art models of Cepheids, we aim to Unlock the projection factor. The BW method, if robust, has the potential in the next decade to test the Hubble tension, by providing the distance of Cepheids in the Local Group (LG) and beyond, individually, using the spectroscopic capabilities of ANDES and MOSAIC instruments at the focus of the ELT.

Being affected throughout their lifetime by a strong mass-loss due to radiative winds, fast rotation, and a high binarity rate, massive stars pose several challenges to the understanding of their observational properties and evolution. The aim of our project is to improve our knowledge of these objects by coupling state-of-the-art two-dimensional simulations of stellar interiors including rotation, pulsations, and mass-loss, with radiative transfer models of their atmospheres and environment, in order to compare the resultant predictions with observations at the highest spectral and angular resolutions. This unique combination of fundamental modelling, radiative transfer, and confrontation with observations will enable us to improve the models of massive stars, as well as our understanding of the underlying physics. Our project relies on the successes of the ESTER code (Toulouse), which models rapidly rotating early-type stars in two-dimensions, and of the TOP pulsation code (Paris-Meudon) for carrying out asteroseismic inferences. From the combination of these codes with radiative transfer models for the atmosphere and the circumstellar environment (winds and disks, which can be composed of gas and dust), we will create a complete and physically consistent modelling tool of massive stars (typically with masses between 4 and 20 solar masses). This physical model will allow us to simulate polychromatic images from which several observables can be computed, in particular those for long baseline optical/infrared spectro-interferometry. We will use this model to compute and deliver to the community, improved grids of models of typical massive stars (interiors, atmospheres, and extended environment). Tools to use these model grids for the analysis of spectro-interferometric data (innovative imaging and model fitting methods) will be developed/adapted for the project and also provided to the community. In addition to these models and dedicated analysis tools, the success of our project for a deep physical study of massive stars relies on the unique expertise in the development and exploitation of spectro-interferometric instruments in Nice, in particular MATISSE, the new mid-infrared instrument of the Very Large Telescope Interferometer (VLTI) array at ESO-Paranal, and SPICA, the upcoming visible beam-combiner for the Center for High Angular Resolution Astronomy (CHARA) array at Mount Wilson Observatory. From our physical analysis of many existing and near-to-come spectro-interferometric data, we will be able to constrain many key parameters defining the central star (mass, temperature, age, rotation rate...) and its environment (mass-loss, and wind and disk structures, i.e. density and temperature law, chemistry, dynamics) of about 200 stars from our survey list. In particular, we will obtain a detailed view (including models and reconstructed images) of about 25 primary targets, which will constitute a unique set of landmark massive stars, spanning different types (e.g. classical Be, B[e], fast rotators, beta Cephei stars, slowly rotating B stars, supergiants). The results of this unprecedented study will also provide invaluable information for a global, unified understanding of the structure and evolution of massive stars.