STA, the Space Trajectory Analysis Project

This article describes the objectives of the Space Trajectory Analysis (STA) project. The article also details the birth of STA, and its present configuration. STA is a project to develop an open source astrodynamics software suite involving university science departments and space research institutions. It was initiated by ESA as internal activity in 2005 and now it involves 16 partners. The article explains the partnership into the STA Steering Board. The main purpose of the STA is to allow advanced simulation for the analysis of space trajectories in an open and free environment under the premises of innovation and reliability.Further, the article explains that the STA development is open source and is based on the state of the art astrodynamics routines that are grouped into modules. Finally, the article concludes about the benefits of the STA initiative: the STA project allows a strong link among applied mathematics, space engineering, and informatics disciplines by reinforcing the academic community with requirements and needs coming from real missions

Spatial and Temporal Trends of Global Pollination Benefit

Pollination is a well-studied and at the same time a threatened ecosystem service. A significant part of global crop production depends on or profits from pollination by animals. Using detailed information on global crop yields of 60 pollination dependent or profiting crops, we provide a map of global pollination benefits on a 5′ by 5′ latitude-longitude grid. The current spatial pattern of pollination benefits is only partly correlated with climate variables and the distribution of cropland. The resulting map of pollination benefits identifies hot spots of pollination benefits at sufficient detail to guide political decisions on where to protect pollination services by investing in structural diversity of land use. Additionally, we investigated the vulnerability of the national economies with respect to potential decline of pollination services as the portion of the (agricultural) economy depending on pollination benefits. While the general dependency of the agricultural economy on pollination seems to be stable from 1993 until 2009, we see increases in producer prices for pollination dependent crops, which we interpret as an early warning signal for a conflict between pollination service and other land uses at the global scale. Our spatially explicit analysis of global pollination benefit points to hot spots for the generation of pollination benefits and can serve as a base for further planning of land use, protection sites and agricultural policies for maintaining pollination services

Alternative futures for global biological invasions

Scenario analysis has emerged as a key tool to analyze complex and uncertain future socio-ecological developments. However, currently existing global scenarios (narratives of how the world may develop) have neglected biological invasions, a major threat to biodiversity and the economy. Here, we use a novel participatory process to develop a diverse set of global biological invasion scenarios spanning a wide range of plausible global futures through to 2050. We adapted the widely used “two axes” scenario analysis approach to develop four families of four scenarios each, resulting in 16 scenarios that were later clustered into four contrasting sets of futures. Our analysis highlights that socioeconomic developments and technological innovation have the potential to shape biological invasions, in addition to well-known drivers, such as climate and human land use change and global trade. Our scenarios partially align with the shared socioeconomic pathways created by the climate change research community. Several factors that drive differences in biological invasions were underrepresented in the shared socioeconomic pathways; in particular, the implementation of biosecurity policies. We argue that including factors related to public environmental awareness and technological and trade development in global scenarios and models is essential to adequately consider biological invasions in global environmental assessments and thereby obtain a more integrative picture of future social–ecological developments

eNLP: Application-Centric NLP-Based Optimization in the Aerospace Market

International audience1.Introduction 2.TEC-ECM Role & Responsibilities 3.Optimal Control Application Examples 4.Description of Optimization Architecture to Solve OCP 5.Low-Thrust GTO-GEO Transfer Optimization 6.GTO-GEO Practical Consideration 7.New European NLP Solver eNLP 8.Conclusion

Entwicklung eines Algorithmus' zur postoptimalen Analyse der Lösung von Optimalsteuerungsproblemen

The description of technical problems in the form of optimal control problems is becoming increasingly popular. And the assessment and evaluation of the obtained optimal solutions is developing into a key competence. This dissertation departs from such an optimal solution. By means of post-optimality analysis an earlier obtained optimal solution is processed, in order to allow a user to efficiently produce information about optimality criteria, the main factors that influence the solution and, in consecutive steps about neighboring solution spaces. The developed algorithm exploits methods from the domain of nonlinear optimization for the transcription of the optimal control problem. This procedure is made generic in the sense that different parameterization schemes are incorporated, ranging from collocation to multiple shooting. The basis of consecutive post-optimality analysis is a parameterized sensitivity analysis. First and second order evaluation takes efficiently advantage of data that has already been computed during the process of the prior optimization. Data that is not readily available, like the Hesse matrix is newly computed. The developed algorithm identifies sensitivities of the cost function within the existing problem description, but also permits to investigate the influence of variations in non optimizable parameters, equality or inequality constraints on the solution space. The latter includes the prediction of changes in the active set of constraints due to finite variations. Under full consideration of optimality conditions and the trust radius, the solution of neighboring problems is predicted. Thus, post-optimality analysis is not only suitable for evaluation of already computed optimal solutions. It also provides an efficient alternative to consecutive optimization of varied problem descriptions. In order to demonstrate the benefits of post-optimality analysis for modern comprehensive problems, the algorithm is applied to two typical aerospace problems. These are an optimal entry of the reusable launch vehicle HOPPER, and ascent trajectories of Ariane 5 with several payload configurations. Robustness and cost quality of the current design is evaluated and potential for improvement quantified. Further, the added value is demonstrated that the newly developed algorithm for post-optimality analysis provides in the area of optimal control problems.Die Beschreibung von technischen Fragestellungen in Form von Optimalsteuerungsproblemen wird zunehmend zu einem populären Werkzeug. Dabei zeigt sich, dass die Aufbereitung und Auswertung der gefundenen optimalen Lösung eine Schlüsselkompetenz darstellt. Die vorgelegte Arbeit setzt hier an. Mittels post-optimaler Analyse wird eine zuvor ermittelte optimale Lösung so weiterverarbeitet, dass der Anwender auf effizientem Wege zusätzliche Daten über Optimalitätsverhalten, Einflussfaktoren und, in weiteren Schritten, über benachbarte Lösungsräume erhält. Der entwicklte Algorithmus nutzt Verfahren aus der Nichtlinearen Optimierung zur Transkription des Optimalsteuerungsproblems. Dieser Vorgang ist insofern generisch gehalten, als verschiedene Parametrisierungsschemata der Kollokation, wie auch der Mehrzielverfahren implementiert sind. Eine darauf aufbauende parametrisierte Sensitivitätsanalyse dient als Grundlage für die eingehende post-optimale Analyse. Für die Untersuchungen erster und zweiter Ordnung wird zur Effizienzsteigerung und Erhöhung der Transparenz, soweit möglich, auf bereits vorhandene Basisdaten zurückgegriffen. Nicht verfügbare Daten, wie etwa Hesse-Matrix, werden neu berechnet. Der entwickelte Algorithmus identifiziert Sensitivitäten der Kostenfunktion innerhalb der bestehenden Problembeschreibung und erlaubt darüber hinaus Aussagen zur Beeinflussung des Lösungsraumes durch die Variation nicht optimierbarer Parameter bzw. Gleichungs- oder auch Ungleichungsbeschränkungen. Letztere Fähigkeit schließt die Prädiktion des Einflusses von finiten Variationen auf die Zusammensetzung des Set der aktiven Beschränkungen ein. Daraus wird dann unter Einschluß von Optimalitätsaspekten und Angabe über den Vertrauensbereich, die Lösung benachbarter Entwurfsräume vorhergesagt. Damit ist die post-optimale Analyse nicht nur zur besseren Bewertung bereits ermittelter Lösungen geeignet, sondern bietet auch eine effiziente Alternative zur konsekutiven Optimierung, variierter Problemstellungen. Um den Nutzen der post-optimalen Analyse für umfassende, moderne Anwendungen zu demonstrieren, wird der neue Algorithmus auf zwei typische Probleme aus der Raumfahrt angewendet. Es handelt sich um die optimale Wiedereintrittsbahn des wiederverwendbaren Transportfahrzeuges HOPPER, sowie um optimale Aufstiegsbahnen einer Ariane 5 bei unterschiedlichen Nutzlast-Konfigurationen. Dabei werden Robustheit und Güte der bisherigen Entwürfe bewertet und das Verbesserungspotential quantifiziert. Außerdem wird demonstriert, welchen zusätzlichen Nutzen der neu entwickelte Algorithmus zur post-optimalen Analyse im Bereich von Optimalsteurungsproblemen hat

Concept-of-operations disposal analysis of spacecraft by gossamer structure

A gossamer structure for end-of-life disposal of spacecraft to mitigate space debris is considered in comparison with other end-of-life disposal concepts to determine when it would be preferable. A needs analysis, potential use cases, and concept-of-operations are developed. A survey of disposal strategies is presented for comparison prior to a down-selection of viable competing techniques; solar sailing, high and low-thrust propulsion, and electrodynamic tethers. A parametric comparison of the down-selection competing techniques is presented. Exploiting solar radiation pressure on the structure is of limited value. Atmospheric drag augmentation was found to be of most benefit for end-of-life disposal when an entirely passive means is required, allowing the gossamer device to act as a ‘fail-safe’. This is applicable to only low and medium mass spacecraft, or spacecraft that are unlikely to survive atmospheric re-entry, hence minimizing risk to human life. It does not significantly alter the operating ceiling altitude but does the maximum allowable end-of-life mass. Peak mass benefit occurs in the altitude range 550 – 650 km and is largely independent of de-orbit time

Infrared Spectroscopy Reveals Metal independent Carbonic Anhydrase Activity in Crotonyl CoA Carboxylase/Reductase

The conversion of CO2 by enzymes such as carbonic anhydrase or carboxylases plays a crucial role in many biological processes. However, methods following the conversion of CO2 at the active site in situ are limited. Here, we used infrared spectroscopy to study the interaction of CO2, water, and other reactants with β-carbonic anhydrase from Escherichia coli (EcCA) and crotonyl-CoA carboxylase/reductase from Kitasaospora setae (KsCcr), two of the fastest CO2-converting enzymes in nature. Our data reveal that KsCcr possesses a so far unknown metal-independent CA-like activity. Site-directed mutagenesis of conserved active site residues allows identifying an ‘activated’ water molecule, forming the hydroxyl anion that attacks CO2 and yields bicarbonate (HCO3–). Molecular dynamics simulations are analyzed to trace CO2 in the active site of KsCcr and explain why substrate binding inhibits the anhydrase activity. Altogether, we demonstrate how in situ infrared spectroscopy combined with molecular dynamics simulations provides a simple, yet powerful new approach to investigate the atomistic reaction mechanisms of different enzymes with CO2