French Space Research Articles

Women, Horses and Dogs. A Reading of Sorana Gurian's Novel from the Animal Studies Perspective

Sorana Gurian's proverbial passion for pets, almost unnoticed in Romanian literary history, deserves a careful analysis, especially because it was directly recognized as and even constituted the foundation of some substantial pages of memoir or fiction prose, written by this cosmopolite, intriguing, and spectacular author, who linked her biographical existence to several Moldavian, Romanian and French spaces. Animals have a completely exceptional importance especially in the novel "The days never come back" (1945) – where the number of animal references is huge (compared to any other Romanian fictional prose, regardless of the era in which they were written). The text contains over two hundred references to dogs and their equivalents from the general semantic field (puppy, whelp), or from the particular one (basset, greyhound, borzoi, fox, etc.), over a hundred references to horses and several hundred other references to cats, rodents (mice, voles, rats, ferrets), birds (from swallows or sparrows to eagles) and insects of various kinds (from crickets to dragonflies). Of all these species, dogs and horses – by far, the protagonists' (Vivian, Ann and her father, nicknamed the Chief) favorites – are frequently particularized even nominally, because from the perspective of the doctor's extended family, they are true friends and communication partners, with rights sometimes superior to servants, acquaintances, or human friends. Far from being perceived as fictional ”commodity objects” or simple tools, used only to build or furnish the narrative world, animals are integrated, to varying degrees, in the families of main characters, they accompany, silently but expressively, their steps – either as partners with equal rights, either as identity doubles or complements – and even reflect, metonymically, the human's narrative evolution. Starting from these premises, my study (which combines elements of gender, trauma, and animal studies) will analyze both the various functions of the numerous elements of bestiary and animal characters, and the provocative stakes of their narrative valorization.

Treatment of epistemic uncertainty in conjunction analysis with Dempster-Shafer theory

The paper presents an approach to the modelling of epistemic uncertainty in Conjunction Data Messages (CDM) and the classification of conjunction events according to the confidence in the probability of collision. The approach proposed in this paper is based on Dempster-Shafer Theory (DSt) of evidence and starts from the assumption that the observed CDMs are drawn from a family of unknown distributions. The Dvoretzky–Kiefer–Wolfowitz (DKW) inequality is used to construct robust bounds on such a family of unknown distributions starting from a time series of CDMs. A DSt structure is then derived from the probability boxes constructed with DKW inequality. The DSt structure encapsulates the uncertainty in the CDMs at every point along the time series and allows the computation of the belief and plausibility in the realisation of a given probability of collision. The methodology proposed in this paper is tested on a number of real events and compared against existing practices in the European and French Space Agencies. We will show that the classification system proposed in this paper is more conservative than the approach taken by the European Space Agency but provides an added quantification of uncertainty in the probability of collision.

Probabilistic risk assessment: Hazard impact study of safety-critical space launch events onto world air traffic & creation of ADIONA software

Space and air traffic increase yearly, prompting concerns about their coexistence. Fallback and splashdown of rocket stages to earth into predefined areas is a usual scenario, explosions of rockets and fallback into unprecedented areas is a probable scenario. These events represent a threat to world air traffic. In the present study, a probabilistic risk assessment on the launcher's stages fallback onto world air traffic has been carried out. A novel method and software, ADIONA, were developed to assess risks of rocket explosions and debris impact on air traffic. This pioneering software, a venture of the Flight Safety Department of the French Space Agency (CNES), supervising European Space Agency (ESA) launches, calculates at every possible time instant, defined by the user, the estimated positions of airplanes with along their own trajectories, trajectories and positions of rockets and the corresponding areas where debris falls back on earth after an explosion or a deviation. It further assesses the risks of fall down of debris on air traffic in case of a launch mishap and the probability of fatality to an airplane regarding the risk boundaries set by the French Space Operations Act. The software has been implemented in a general way for broad future application in operations and continued studies and use. Real-world air traffic and rocket launch data were incorporated, particularly focusing on launches from the French Guiana Space Center (CSG) and air traffic over the North Atlantic Ocean. These real-world analyses represent realistic scenarios. The obtained results show a considerable high possible risk onto world air traffic in case of a rocket explosion after launch. It is concluded that the cohabitation of space and air traffic and the probabilistic risk assessment thereof is important to be monitored in order to eventually be diminished to reduce the risk. It is recommended to invest further resources into this observation type of analysis. Further investigations should take place on this probabilistic risk analysis, taking into account more details and fine-tuning in the risk calculation and assessment method. The study's findings and software lay the groundwork for future risk analysis and development, facilitating ongoing and future investigations.

A Kriging-based method for the efficient computation of debris impact zones

To prevent or assess launch risk, evaluation of launchers impact zones is a key element. Several methods are currently used to predict impact zones at the French space agency (CNES), but the highest-fidelity method uses a series of computationally costly Monte Carlo simulations. This process can be very time consuming and the computation time can become prohibitive. A machine learning method called Kriging or Gaussian Process Regression is studied as a potential avenue to speed up the impact zones evaluation. This Kriging-based method, is tested in this paper in different flight phases and its potential for estimating debris impact zones is evaluated in terms of processing time, accuracy and genericity.

Non-destructive evaluation of the curing of a polybenzoxazine nanocomposite blend for space applications using fluorescence spectroscopy and predictive mechanical modelling

In this study, we employ fluorescence spectroscopy to monitor the curing process of a novel polybenzoxazine (PBZ) resin blend containing a polyhedral oligomeric silsesquioxane (POSS) reagent in a non-destructive way and compare it with the differential scanning calorimetry data. Our resin blend has been carefully selected for study on the International Space Station in 2024 as part of the Euro Materials Ageing 1 Programme (AO-2020-EMA) supported by the European Space Agency (ESA) and the French Space Agency (CNES). Computational simulations of PBZ-POSS blend composites are investigated to determine their effective mechanical responses based on constituent micro-stresses with periodic boundary conditions and continuum-based analytical micromechanical models. Further investigations are focused on the development of different representative volume element models, including periodic, non-periodic, and overlap inclusions, and the comparison with experimental data. Fluorescence spectroscopy and computational and analytical methods can offer a non-destructive approach to gaining insights into polymerisation processes and effective mechanical responses.

The CNES Solutions for Improving the Positioning Accuracy with Post-Processed Phase Biases, a Snapshot Mode, and High-Frequency Doppler Measurements Embedded in Recent Advances of the PPP-WIZARD Demonstrator

For many years, the navigation team at the French Space Agency (CNES) has been developing its Precise Point Positioning project. The goal was initially to promote a technique called undifferenced ambiguity resolution. One of the main characteristics of this technique is the capability for a user receiver to perform centimeter-level accuracy in real time. To do so, a demonstrator has been built. Its architecture is composed of three main elements: a correction processing software called the server part, a means to transmit the corrections using standardized messages, and a user software capable of handling the corrections to compute an accurate positioning at the user level. In this paper, we present the recent advances in the CNES precise point positioning demonstrator. They are composed of some evolution of the network of stations and server software, the implementation of the new state space representation standard, a new method for instantaneous ambiguity resolution using uncombined four-frequency signals, its implementation in real-time at the server and the user level, and the use of high-rate Doppler measurements to improve the accuracy of the solution in harsh urban environments. On top of that, the computation of high-accuracy post-processed phase biases with the majority of current GNSS signals supported, compatible with the uncombined method and a new online positioning service to demonstrate the capacity of the user software, is demonstrated.

Euro Material Ageing – Ground-based testing and selection of the ESA flight candidate materials

One of the newest European additions to the International Space Station (ISS) is the Airbus Bartolomeo payload hosting platform, attached externally to the European Columbus Module. This will provide an unobstructed access to the external space environment offering research opportunities for a wide range of space science applications. One of the Bartolomeo missions under development is Euro Material Ageing (EMA) – a joint collaboration between the European Space Agency (ESA) and the French Space Agency (CNES). ESA is using the Bartolomeo platform as a testing opportunity to perform materials science research and calibrate its ground-based testing facilities against the real space environment. Additionally, it offers a unique opportunity to small space players of the European market for direct in-flight technology validation.

Inclusive writing

This article documents the linguistic, disciplinary, geographical and ideological circulation of the notion of ‘inclusive writing/d’écriture inclusive’ in order to understand the French controversy surrounding the term. The article shows that North American Protestant feminist theologists first spread the expression in the 1970s. The expression then circulated in feminist circles in English and French, in Europe and North America, but also in the fields of disability and pedagogy. Its success in the French space, however, is not only due to its Protestant roots but also to a republican definition of inclusion emerging in France in the 1990s. By the time the controversy shot up, the paradigm of inclusion was thus loaded with its French republican meaning as much as its English and/or North American meaning, creating an ideological paradox that limits inclusive writing’s critical capacity and fails to question relations of domination.

Current observed global mean sea level rise and acceleration estimated from satellite altimetry and the associated measurement uncertainty

Abstract. We present the latest release of the global mean sea level (GMSL) record produced by the French space agency Centre National d’Etudes Spatiales (CNES) and distributed on the AVISO+ website. This dataset is based on reprocessed along-track data, so-called L2P 21, of the reference missions TOPEX/Poseidon (TP) and Jason-1, Jason-2 and Jason-3. The L2P 21 CNES/AVISO+ GMSL record covers the period January 1993 to December 2021 and is now delivered with an estimate of its measurement uncertainties following the method presented in Ablain et al. (2019). Based on the latest calibration (Cal) and validation (Val) knowledge, we updated the uncertainty budget of the reference altimetry mission measurements and demonstrate that the CNES/AVISO+ GMSL record now achieves stability of performances of ± 0.3 mm yr−1 at the 90 % confidence level (C.L.) for its trend and ±0.05 mm yr−2 (90 % C.L.) for its acceleration over the 29 years of the altimetry record. Thanks to an analysis of the relative contribution of each measurement uncertainty budget contributor, i.e. the altimeter, the radiometer, the orbit determination and the geophysical corrections, we identified the current limiting factors to the GMSL monitoring stability and accuracy. We find that the radiometer wet troposphere correction (WTC) and the high-frequency errors with timescales shorter than 1 year are the major contributors to the GMSL measurement uncertainty over periods of 10 years (30 %–70 %), for both the trend and acceleration estimations. For longer periods of 20 years, the TP data quality is still a limitation, but more interestingly, the International Terrestrial Reference Frame (ITRF) realization uncertainties becomes dominant over all the other sources of uncertainty. Such a finding challenges the altimetry observing system as it is designed today and highlights clear topics of research to be explored in the future to help the altimetry community to improve the GMSL measurement accuracy and stability.

A Framework for Estimating Global River Discharge From the Surface Water and Ocean Topography Satellite Mission

AbstractThe Surface Water and Ocean Topography (SWOT) mission will vastly expand measurements of global rivers, providing critical new data sets for both gaged and ungaged basins. SWOT discharge products (available approximately 1 year after launch) will provide discharge for all river that reaches wider than 100 m. In this paper, we describe how SWOT discharge produced and archived by the US and French space agencies will be computed from measurements of river water surface elevation, width, and slope and ancillary data, along with expected discharge accuracy. We present for the first time a complete estimate of the SWOT discharge uncertainty budget, with separate terms for random (standard error) and systematic (bias) uncertainty components in river discharge time series. We expect that discharge uncertainty will be less than 30% for two‐thirds of global reaches and will be dominated by bias. Separate river discharge estimates will combine both SWOT and in situ data; these “gage‐constrained” discharge estimates can be expected to have lower systematic uncertainty. Temporal variations in river discharge time series will be dominated by random error and are expected to be estimated within 15% for nearly all reaches, allowing accurate inference of event flow dynamics globally, including in ungaged basins. We believe this level of accuracy lays the groundwork for SWOT to enable breakthroughs in global hydrologic science.

FGS, a multi-mission space gamma-ray spectrometer: Design optimization and first results

Following the failure of the TARANIS (Tool for the Analysis of RAdiation from lightNIng and Sprites) mission launch[1], the French space agency (CNES) funded a R&D program with APC and LESIA laboratories to develop a new gamma-ray spectrometer. The first studies started in 2021 and lead to a new design called FGS (Fast Gamma-ray Spectrometer) based on new GAGG scintillators readout by SiPM and analysed by the IDEAS/APOCAT fast ASIC. This program’s main objective is to build a space qualified FGS prototype before 2024. FGS scientific specifications are based on Terrestrial Gamma-ray Flashes (TGF) science studies but this spectrometer could also be used or optimized for other missions: solar science, astrophysical observations (Gamma-Ray Bursts) or planetology studies. The main instrumental objectives are to detect gamma rays in the [20keV–20MeV] energy range with high count rate abilities and a large detection surface. In this paper, we will present our FGS concept and the first spectroscopic results we obtained, consistent on ground with our scientific requirements.

Impact of the Antenna Spacing on the Brightness Temperature Maps Retrieved with a Synthetic Aperture Imaging Radiometer

For almost five years, phase 0 and phase A studies have been conducted by the French space agency for a second generation of the Soil Moisture and Ocean Salinity (SMOS) satellite devoted to a High Resolution (HR) follow-on mission. Within the frame of the preliminary results obtained with a candidate array for this SMOS-HR project, this contribution focuses on what could happen to any synthetic aperture imaging radiometer when the shortest spacing between the antennas of the interferometric array becomes smaller than a geometrical limit below which the synthesized field of view seems to be wider than the field of view seen by each elementary antenna. It is shown that in such a situation, the inversion of the complex visibilities becomes unstable in presence of noise and this instability is characterized by the undesirable presence of a phantom in the retrieved brightness temperature maps. The origin of this phantom is explained and a solution to cure the interferometric array from that issue is proposed and assessed with the aid of numerical simulations.

Refining the Resolution of DUACS Along-Track Level-3 Sea Level Altimetry Products

This paper describes the demonstration of a regional high-resolution level-3 (L3) altimeter data unification and altimeter combination system (DUACS) developed with support from the French space agency (CNES). Deduced from full-rate (20 Hz to 40 Hz) level-2 (L2) altimeter measurements, this product provides sea level anomalies (SLA) and other essential physical variables at a spatial resolution of one sample every ~1 km over the North Atlantic Ocean. This allows us to resolve wavelengths from ~35 km to ~55 km depending on the altimeter considered. This was made possible by recent advances in radar altimeter processing for both synthetic aperture radar (SAR) and low-resolution-mode (LRM) measurements, as well as improvements made to different stages of the DUACS processing chain. Firstly, the new adaptive and low-resolution with range migration correction (LR-RMC) processing techniques were considered for Jason and Sentinel-3 (S3A), respectively. They significantly reduce errors at short wavelengths, and the adaptive processing also reduces possible land contamination near the coast. Next, up-to-date geophysical and environmental corrections were selected for this production. This includes specific corrections intended to reduce the measurement noise on LRM measurements and thus enhance the observability at short wavelengths. Compared with the 1 Hz product, the observable wavelengths reached with the demonstration high-resolution product are reduced by up to one third, or up to half in the northeast Atlantic region. The residual noises were optimally filtered from full-rate measurements, taking into consideration the different observing capabilities of the altimeters processed. A specific data recovery strategy was applied, significantly optimizing the data availability, both in the coastal and open ocean areas. This demonstration L3 product is thus better resolved than the conventional 1 Hz product, especially near the coast, where it is defined up to ~5 km against ~10 km for the 1 Hz version. Multi-mission cross-calibration processing was also optimized with an improved long-wavelength error (LWE) correction, leading to a better consistency between tracks, with a 9–15% reduction in SLA variance at cross-overs. The new L3 product improves the overall consistency with tide gauge measurements, with a reduction in SLA differences variance by 5 and 17% compared with the 1 Hz product from the S3A and Jason-3 (J3) measurements, respectively. Primarily intended for regional applications, this product can significantly contribute to improving high-resolution numerical model output via data assimilation. It also opens new perspectives for a better understanding of regional sea-surface dynamics, with an improved representation of the coastal currents and a refined spectral content revealing the unbalanced signal.

Multi-maneuver algorithms for multi-risk collision avoidance via nonconvex quadratic optimization

In this article, the problem of modeling and computing the optimal collision avoidance maneuvers for multiple short-term encounters is presented. Several metrics defining the overall collision risk are analyzed. These include imposing lower bounds on the miss-distance or the Mahalanobis distance at each corresponding time of closest approach (TCA) or upper-bounds on the collision probability. The avoidance maneuvers are modeled as impulsive ones in a single direction of the local frame and for a priori fixed dates for operational motivations. Station-keeping constraints are also imposed via linear inequalities on the relative states at each TCA. The specific nature of the imposed constraints is dictated by a practical framework provided by the French Space Agency (CNES). This results in formulating the maneuver design problem as an optimization problem with linear objective and non-convex quadratic constraints. Different algorithms are presented to solve this problem. Finally, the relative efficiency of the proposed approaches is evaluated and analyzed on a realistic conjunction built from data extracted from the CNES database and on academic random examples of higher complexity.

Analysis of CNES’ scientific production in aerospace research: 60 years of commitment with the future

CNES (Centre National d'Études Spatiales) acts, since its creation in 1961, as the French Space Agency and is a key leader in space research, and scientific and technical developments. Its involvement in a broad range of programs has positioned CNES as one of the most relevant national research agencies, leading efforts and initiatives in both European and international contexts. This article provides a review and analysis of the scientific and technical production of CNES, using as input the papers written by CNES staff referenced in the Scopus database. The period under study dates to 1964 and includes more than 10.000 documents. The study analyses measurable characteristics of CNES documents’ production: productivity, collaboration, and impact through citations. This paper provides a contribution aimed to gain a better understanding and characterisation of the scientific activity completed by Space agencies.

CNES-ESA satellite contribution to the operational monitoring of volcanic activity: The 2021 Icelandic eruption of Mt. Fagradalsfjall

Within the framework of the CIEST2 (Cellule d'Intervention d'Expertise Scientifique et Technique new generation) and thanks to the support of CNES, the French space agency, the first phase of the Fagradalsfjall eruption was exceptionally well covered by high resolution optical satellite data, through daily acquisitions of Pléiades images in stereo mode. In this study, we show how Pléiades data provided real-time information useful for the operational monitoring of the ongoing eruption. An estimation of the volume of lava emitted as well as the corresponding effusion rate could be derived and delivered to the civil protection less than 6 h after the data acquisition. This information is complementary to and consistent with estimates obtained through the HOTVOLC service using SEVIRI (Spinning Enhanced Visible and Infrared Imager) sensor on-board Meteosat Second Generation (MGS) geostationary satellites, operated by the European Space Agency (ESA), characterized by a lower spatial resolution and a higher temporal one. In addition to the information provided on the lava emission, Pléiades data also helped characterize the intensity of the eruption by providing insight into the elevation and the velocity of the volcanic plume. The survey of this effusive eruption, well anticipated by a series of precursors, is a proof of concept of the efficiency of optical/thermal satellite data for volcanic crisis real-time monitoring.

Reimagining the Surface Water and Ocean Topography Mission as the “Landsat” of Surface Water [Perspective

The Surface Water Ocean Topography (SWOT) mission, jointly developed by NASA and French Space Agency (CNES) with contributions from the Canadian and U.K. space agencies, and planned for launch in 2022, is designed to provide a spatially distributed and high-frequency measurement of water elevation data for the hydrology and oceanography communities for the first time <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> , <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> . By virtue of its novel observational capability and stated scientific goals, SWOT satellite data are expected to have a profound impact on our understanding of global surface water. Although there have been many satellite missions that can either map water extent or water elevation, SWOT is the first mission that will measure extent and elevation concurrently regardless of cloud cover conditions and with a higher degree of precision.

Parameter estimation of a gyroless micro-satellite from telemetry data

This paper presents a new approach for the simultaneous inertia and actuator alignment parameter estimation. One of the strengths of the proposed estimation algorithm consists in its ability to work directly with the star tracker attitude measurements and it is therefore also suitable for small and medium size satellites, where the gyroscope measures are not reliable or not available. In the algorithm, the satellite inverse dynamics model is exploited for the estimation cost function to take advantage of the linearity with respect to the main satellite parameters. The overall proposed solution is based on the instrumental variable method which has been deeply adapted to take into account several practical issues. The main components of the disturbance torques are modeled and simultaneously estimated with the satellite parameters to compensate for their effect. Inspired by the prefiltering technique used in the optimal refined instrumental variable method, a tailor-made filter design is proposed and implemented to deal with noisy measurements and the unmodeled disturbance torques. Such prefilter considerably improves the algorithm performance by achieving low-variance parameter estimates, while still requiring little to no tuning. A final but important novelty of this work consists in proposing an effective solution for estimating and compensating synchronism errors in the sensor measurements. This latter aspect has never been considered in the literature, although the lack of synchronism has a non-negligible effect on the accuracy of the parameter estimates. The proposed method is analyzed and validated via Monte Carlo simulations using data coming from a high-fidelity satellite simulator designed by the French space agency, and the results show the effectiveness of the algorithm.

Aluminum concentration range for the extrudability of ceramic pastes

With the goal of developing refractory pastes to replace metal alloys used in turbine blades for Deep Space exploration, the French Space Agency, CNES, in collaboration with the Institute of Research for Ceramics, IRCER, has developed a preliminary research where dense alumina ceramics were formulated, printed and tested. This preliminary research will be the prelude to substituting by materials with more interesting creep properties at high temperature, for example, yttrium aluminum garnet, YAG. Since alumina is less expensive than YAG, preliminary tests were performed with alumina. These alumina pastes were 3D-printed by robocasting from very high solid loaded alumina pastes (>75 wt%), in the presence of organic additives, namely glycerol, PVA and ISOBAM 104. Several formulations of pastes were prepared, with the aim to obtain dense ceramic pieces. After, the alumina and the organic additives were mechanically mixed and the pastes were extruded with a commercial 3D printer. The best sample was obtained with a paste presenting an Al2O3 solid load of 79.37 wt% (63.5 vol%). A debinding step was performed afterwards to eliminate their organic content and the consolidation of the shaped pieces was finally achieved by sintering at 1700 °C. A % shrinkage of 8, 6.8 and 13.8 in the X, Y and Z-axes was measured, being one of the lowest values at 1700 °C compared to those in the literature.

Early Deconditioning of Human Skeletal Muscles and the Effects of a Thigh Cuff Countermeasure.

Muscle deconditioning is a major consequence of a wide range of conditions from spaceflight to a sedentary lifestyle, and occurs as a result of muscle inactivity, leading to a rapid decrease in muscle strength, mass, and oxidative capacity. The early changes that appear in the first days of inactivity must be studied to determine effective methods for the prevention of muscle deconditioning. To evaluate the mechanisms of muscle early changes and the vascular effect of a thigh cuff, a five-day dry immersion (DI) experiment was conducted by the French Space Agency at the MEDES Space Clinic (Rangueil, Toulouse). Eighteen healthy males were recruited and divided into a control group and a thigh cuff group, who wore a thigh cuff at 30 mmHg. All participants underwent five days of DI. Prior to and at the end of the DI, the lower limb maximal strength was measured and muscle biopsies were collected from the vastus lateralis muscle. Five days of DI resulted in muscle deconditioning in both groups. The maximal voluntary isometric contraction of knee extension decreased significantly. The muscle fiber cross-sectional area decreased significantly by 21.8%, and the protein balance seems to be impaired, as shown by the reduced activation of the mTOR pathway. Measurements of skinned muscle fibers supported these results and potential changes in oxidative capacity were highlighted by a decrease in PGC1-α levels. The use of the thigh cuff did not prevent muscle deconditioning or impact muscle function. These results suggest that the major effects of muscle deconditioning occur during the first few days of inactivity, and countermeasures against muscle deconditioning should target this time period. These results are also relevant for the understanding of muscle weakness induced by muscle diseases, aging, and patients in intensive care.