VV16: The First VEGA Rideshare Mission: Lessons Learnt after Successful Flight

The SSMS (Small Spacecraft Mission Service) program is a new multi-launch concept for the Vega and Vega C launchers, thanks to a new modular dispenser for the Small Satellites Market. The Vega Proof of Concept (POC) flight using the SSMS hardware was developed to provide solutions and services for the 1-400 kg mass class. The SSMS POC mission has successfully flown on VEGA VV16 flight on September 3rd, 2020. The paper describes the lesson learned after this first rideshare mission flight. Vega SSMS first Mission carried 43 different satellites ranging from 1 to 150 Kg from more than 10 different operators. Several challenges had to be dealt with. The missionization process had to be standardized and with increased genericity (ad-hoc margin policy) to cover the continuous changes (of satellites or at least of locations in the dispensers). To simplify and shorten the mission preparation time, from customer side, the satellites designers have tried to adapt to the standardized SSMS interfaces. The trajectory profile is more complex than a standard VEGA single mission. Several main engine boosts are designed to release the satellites in a sequence of separations and collision avoidance maneuvers. The paper presents the outcomes of the successful flight and the information collected from the different measurements. The accelerometers located in the upper part show that the random and shock environment, as well as the low frequency environment, sensed at the levels of the different structures including the satellites, are compatible with the predictions and the specifications. The same good consistency between measurements, predictions and specifications has been found on the thermal properties sensed by the satellites. The separation of the satellites has been observed thanks to different measurements. The inertial navigation system (INS) outputs, which are standard in the telemetry, provide good observation of the separation sequences in terms of direction and norm of the impulses generated by the various separation devices. In addition, dedicated cameras were present to film the satellites immediately after the separation and to check their good respective disposals in terms of attitude and position. The orbital accuracy has also been verified as normal work (by using not only the Navigation information but also the GNSS outputs). It is very good thanks to Guidance algorithms and Navigation performances. In the last chapter of the paper, we also couple the lessons learnt after VV16 flight with the on-going missionization of VV18 (to be flown on April 2021) and VV19 (to be flown on June 2021). They are not strictly speaking full SSMS missions, but they share strong commonalities with VV16 in terms of dispensers for CubeSats separations

VV16: The First VEGA Rideshare Mission Flight

The SSMS (Small Spacecraft Mission Service) program is a new multi-launch concept for the Vega and Vega C launchers, thanks to a new modular dispenser for the Small Satellites Market. The Vega Proof of Concept (POC) flight using the SSMS hardware was developed in the context of ESA LLL Initiative (Light satellite, Low cost, launch opportunities) to provide solutions and services for the 1-400 kg mass class. The SSMS POC mission is foreseen to fly on VEGA VV16 flight on August 2020, following the last flight VV15 in July 2019. The paper describes the lesson learned of this first rideshare mission flight due to late definition or evolution of the satellites aggregate. On one hand the missionization process needs to become more standardized and with increased genericity (ad-hoc margin policy) in order to cover the continuous changes. On the other hand, the satellites should try to adapt to the standardized SSMS interfaces to simplify and shorten the mission preparation time. Based on the accumulated experience of the previous flights, the development of the multi-Payload mission concept started from the analysis of the activities to fly a single payload mission adapted to the needs of multi payload rideshare missions. Aggregation activities partially performed in Europe for the first time and completed in French Guiana, assembling, testing and integration into the Payload fairing, as well as relationships with clients and operators during the flight preparation campaign are not reported in this paper. Vega SSMS first Mission carried 43 different satellites ranging from 1 to 150 Kg from more than 10 different operators; this milestone represents a major advancement towards the goal to provide access to space for Small Satellite

An extremal model for amorphous media plasticity

An extremal model for the plasticity of amorphous materials is studied in a simple two-dimensional anti-plane geometry. The steady-state is analyzed through numerical simulations. Long-range spatial and temporal correlations in local slip events are shown to develop, leading to non-trivial and highly anisotropic scaling laws. In particular, the plastic strain is shown to statistically concentrate over a region which tends to align perpendicular to the displacement gradient. By construction, the model can be seen as giving rise to a depinning transition, the threshold of which (i.e. the macroscopic yield stress) also reveal scaling properties reflecting the localization of the activity.Comment: 4 pages, 5 figure

Applications of liquid chromatography coupled to mass spectrometry-based metabolomics in clinical chemistry and toxicology: A review.

International audienceThe metabolome is the set of small molecular mass organic compounds found in a given biological media. It includes all organic substances naturally occurring from the metabolism of the studied living organism, except biological polymers, but also xenobiotics and their biotransformation products. The metabolic fingerprints of biofluids obtained by mass spectrometry (MS) or nuclear magnetic resonance (NMR)-based methods contain a few hundreds to thousands of signals related to both genetic and environmental contributions. Metabolomics, which refers to the untargeted quantitative or semi-quantitative analysis of the metabolome, is a promising tool for biomarker discovery. Although proof-of-concept studies by metabolomics-based approaches in the field of toxicology and clinical chemistry have initially been performed using NMR, the use of liquid chromatography hyphenated to mass spectrometry (LC/MS) has increased over the recent years, providing complementary results to those obtained with other approaches. This paper reviews and comments the input of LC/MS in this field. We describe here the overall process of analysis, review some seminal papers in the field and discuss the perspectives of metabolomics for the biomonitoring of exposure and diagnosis of diseases

La presse écrite en Ouzbékistan

Dans la conjoncture contemporaine de ré-agencement des nouveaux États indépendants d’Asie centrale, les domaines de compétence entre les diverses branches du pouvoir ne sont pas distinctement répartis et tendent à être éclipsés par la toute-puissance présidentielle. Les médias auraient pu représenter l’un des seuls contrepoids possibles puisque, dès la perestroïka, le “quatrième pouvoir” avait pris son autonomie face au politique et profité de la glasnost’ pour s’autonomiser et porter un rega..

Accelerated Methods for Riemannian Min-Max Optimization Ensuring Bounded Geometric Penalties

In this work, we study optimization problems of the form $\min_x \max_y f(x, y)$, where $f(x, y)$ is defined on a product Riemannian manifold $\mathcal{M} \times \mathcal{N}$ and is $\mu_x$-strongly geodesically convex (g-convex) in $x$ and $\mu_y$-strongly g-concave in $y$, for $\mu_x, \mu_y \geq 0$. We design accelerated methods when $f$ is $(L_x, L_y, L_{xy})$-smooth and $\mathcal{M}$, $\mathcal{N}$ are Hadamard. To that aim we introduce new g-convex optimization results, of independent interest: we show global linear convergence for metric-projected Riemannian gradient descent and improve existing accelerated methods by reducing geometric constants. Additionally, we complete the analysis of two previous works applying to the Riemannian min-max case by removing an assumption about iterates staying in a pre-specified compact set.Comment: added weakly-convex analysis, and some remark