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McInnes C.R.,University of Strathclyde | Bewick R.,Universitatsallee 27 29 | Sanchez J.P.,Polytechnic University of Catalonia
Issues in Environmental Science and Technology | Year: 2014

This chapter provides an overview of space-based geoengineering as a tool to modulate solar insolation and offset the impacts of humandriven climate change. A range of schemes are considered including static and orbiting occulting disks and artificial dust clouds at the interior Sun-Earth Lagrange point, the gravitational balance point between the Sun and Earth. It is demonstrated that, in principle, a dust cloud can be gravitationally anchored at the interior Lagrange point to reduce solar insolation and that orbiting disks can provide a uniform reduction of solar insolation with latitude, potentially offsetting the regional impacts of a static disk. While clearly speculative, the investigation of space-based geoengineering schemes provides insights into the long-term prospects for large-scale, active control of solar insolation. © The Royal Society of Chemistry 2014.

Wagner I.,Karlsruhe Institute of Technology | Braun M.,Universitatsallee 27 29 | Slenzka K.,German Aerospace Center | Posten C.,Karlsruhe Institute of Technology
Advances in Biochemical Engineering/Biotechnology | Year: 2016

Life support systems for long-term space missions or extraterrestrial installations have to fulfill major functions such as purification of water and regeneration of atmosphere as well as the generation of food and energy. For almost 60 years ideas for biological life support systems have been collected and various concepts have been developed and tested. Microalgae as photosynthetic organisms have played a major role in most of these concepts. This review deals with the potentials of using eukaryotic microalgae for life support systems and highlights special requirements and frame conditions for designing space photobioreactors especially regarding illumination and aeration. Mono- and dichromatic illumination based on LEDs is a promising alternative for conventional systems and preliminary results yielded higher photoconversion efficiencies (PCE) for dichromatic red/blue illumination than white illumination. Aeration for microgravity conditions should be realized in a bubble-free manner, for example, via membranes. Finally, a novel photobioreactor concept for space application is introduced being parameterized and tested with the microalga Chlamydomonas reinhardtii. This system has already been tested during two parabolic flight campaigns. © Springer International Publishing Switzerland 2015.

Panopoulou A.,Universitatsallee 27 29 | Fransen S.,European Space Agency | Gomez-Molinero V.,Airbus | Kostopoulos V.,University of Patras
CEAS Space Journal | Year: 2013

The objective of this work is to develop a new structural health monitoring system for composite aerospace structures based on dynamic response strain measurements and experimental modal analysis techniques. Fiber Bragg grating (FBG) optical sensors were used for monitoring the dynamic response of the composite structure. The structural dynamic behavior has been numerically simulated and experimentally verified by means of vibration testing. The hypothesis of all vibration tests was that actual damage in composites reduces their stiffness and produces an eigenfrequency shifting to lower values in the same sense as mass increase produces. Thus, damage was simulated by slightly varying locally the mass of the structure at different zones. The correlation between the simulated damage and the loss of stiffness was analytically defined. Experimental modal analysis based on the strain responses was conducted and the extracted strain mode shapes were the input for the damage detection expert system. A feed-forward back propagation neural network was the core of the damage detection system. The features-input to the neural network consisted of the strain mode shapes, extracted from the experimental modal analysis. Dedicated training and validation activities were carried out based on the experimental results. The system showed high reliability, confirmed by the ability of the neural network to recognize the size and the position of damage on the structure. The experiments were performed on a real structure i.e. a lightweight antenna sub-reflector, manufactured and tested at EADS CASA ESPACIO. An integrated FBG sensor network, based on the advantage of multiplexing, was mounted on the structure with optimum topology. Numerical simulation was used as a support tool at all the steps of the work. Potential applications for the proposed system are during ground qualification extensive tests of space structures and during the mission as modal analysis tool on board, being able via the FBG responses to identify a potential failure. © 2013 CEAS.

Heinkelmann R.,Deutsches Geodatisches Forschungsinstitut DGFI | Tesmer V.,Universitatsallee 27 29
International Association of Geodesy Symposia | Year: 2013

We assess the systematics between Very Long Baseline Interferometry (VLBI) terrestrial and celestial reference frames (TRF and CRF) solutions caused by different analysis options. Comparisons are achieved by sequential variation of options relative to a reference solution, which fulfills the requirements of the International VLBI Service for Geodesy and Astrometry (IVS) analysis coordination. Neglecting the total NASA/GSFC Data Assimilation Office (DAO) a priori gradients causes the largest effects: Mean source declinations differ up to 0.2 mas, station positions are shifted southwards, and heights are systematically larger by up to 3 mm, if no a priori gradients are applied. The effect is explained with the application of gradient constraints. Antenna thermal deformations, atmospheric pressure loading, and the atmosphere pressure used for hydrostatic delay modeling still exhibit significant effects on the TRF, but corresponding CRF differences (about 10 mas) are insignificant. The application of NMF atmosphere mapping functions can systematically affect source declinations up to 30 mas, which is between the estimated axes stability (10 μas) and the mean positional accuracy (40 μas) specified for the ICRF2. Further significant systematic effects are seasonal variations of the terrestrial network scale (±1 mm) neglecting antenna thermal deformations, and seasonal variations of station positions, primarily of the vertical component up to 5 mm, neglecting atmospheric loading. The application of NMF instead of VMF1 can result in differences of station heights up to 6 mm, but no overall global systematic can be found. Using constant atmosphere pressure values for the determination of hydrostatic zenith delays systematically deforms the TRF: station height differences mostly show the same sign with absolute values exceeding 1 mm. © Springer-Verlag Berlin Heidelberg 2013.

Fernandez I.,GTD Sistemas de informacion SA | Di Cerbo A.,Intelligentia srl | Dehnhardt E.,Universitatsallee 27 29 | Massimo T.,Universitatsallee 27 29 | Brunjes B.,Universitatsallee 27 29
European Space Agency, (Special Publication) ESA SP | Year: 2015

This paper describes a testing framework for critical space SW named Technical Specification Validation Framework (TSVF). It provides a powerful and flexible means and can be used throughout the SW test activities (test case specification & implementation, test execution and test artifacts analysis). In particular, tests can be run in an automated and/or step-by-step mode. The TSVF framework is currently used for the validation of the Satellite Control Software (SCSW), which runs on the Meteosat Third Generation (MTG) satellite on-board computer. The main purpose of the SCSW is to control the spacecraft along with its various subsystems (AOCS, Payload, Electrical Power, Telemetry Tracking & Command, etc.) in a way that guarantees a high degree of flexibility and autonomy. The TSVF framework serves the challenging needs of the SCSW project, where a plan-driven approach has been combined with an agile process in order to produce preliminary SW versions (with a reduced scope of implemented functionality) in order to fulfill the stakeholders needs ([1]). The paper has been organised as follows. Section 2 gives an overview of the TSVF architecture and interfaces versus the test bench along with the technology used for its implementation. Section 3 describes the key elements of the XML based language for the test case implementation. Section 4 highlights all the benefits compared to conventional test environments requiring a manual test script development, whereas section 5 concludes the paper.

Wortmann A.,Universitatsallee 27 29 | MacHel G.,Universitatsallee 27 29 | Holsti N.,Tidorum Ltd.
European Space Agency, (Special Publication) ESA SP | Year: 2012

The application of modern object oriented design and modeling techniques on the basis of state charts aid modular and flexible software architectures. On the other hand, a satellite's on-board software drives an efficient embedded system that must satisfy a large number of (hard) real-time requirements. The on-board software of the Small Geo (SGEO) program is designed with a model based approach and the architecture is eventdriven. The challenge taken and presented in this paper is the successful timing verification of a real-time software with event-driven code auto-generated from state charts. Static worst case execution time analysis and feasibility calculations are presented for both hard-realtime-tasks and soft-real-time activities.

Pawlak H.,Universitatsallee 27 29 | Jacob A.F.,TU Hamburg - Harburg
IEEE Transactions on Antennas and Propagation | Year: 2010

A novel calibration scheme is presented that is especially suited for complex digital beamforming (DBF) antenna arrays at millimeter-wave frequencies. Calibration data is extracted by sampling the field of each radiator at certain locations near the array by fixed probe antennas. A scalable calibration model for evaluation of the measured data is described. First tests are performed on a small passive array representing a unit cell of larger arrays. The calibration scheme is subsequently applied to and tested on a 64 element DBF transmit antenna array. © 2009 IEEE.

Tesmer V.,Universitatsallee 27 29 | Steigenberger P.,TU Munich | van Dam T.,University of Luxembourg | Mayer-Gurr T.,University of Bonn
Journal of Geodesy | Year: 2011

Temporal variations in the geographic distribution of surface mass cause surface displacements. Surface displacements derived from GRACE gravity field coefficient time series also should be observed in GPS coordinate time series, if both time series are sufficiently free of systematic errors. A successful validation can be an important contribution to climate change research, as the biggest contributors to mass variability in the system Earth include the movement of oceanic, atmospheric, and continental water and ice. In our analysis, we find that if the signals are larger than their precision, both geodetic sensor systems see common signals for almost all the 115 stations surveyed. Almost 80% of the stations have their signal WRMS decreased, when we subtract monthly GRACE surface displacements from those observed by GPS data. Almost all other stations are on ocean islands or small peninsulas, where the physically expected loading signals are very small. For a fair comparison, the data (79 months from September 2002 to April 2009) had to be treated appropriately: the GPS data were completely reprocessed with state-of-the-art models. We used an objective cluster analysis to identify and eliminate stations, where local effects or technical artifacts dominated the signals. In addition, it was necessary for both sets of results to be expressed in equivalent reference frames, meaning that net translations between the GPS and GRACE data sets had to be treated adequately. These data sets are then compared and statistically analyzed: we determine the stability (precision) of GRACE-derived, monthly vertical deformation data to be ~1.2 mm, using the data from three GRACE processing centers. We statistically analyze the mean annual signals, computed from the GPS and GRACE series. There is a detailed discussion of the results for five overall representative stations, in order to help the reader to link the displayed criteria of similarity to real data. A series of tests were performed with the goal of explaining the remaining GPS-GRACE residuals. © 2011 Springer-Verlag.

Wortmann A.,Universitatsallee 27 29 | MacHel G.,Universitatsallee 27 29 | Gunther L.,Universitatsallee 27 29 | Schumann D.,Universitatsallee 27 29
European Space Agency, (Special Publication) ESA SP | Year: 2012

The Small Geo (SGEO) program is a geostationary satellite platform for comparatively small telecommunication missions with a payload in the 300kg / 3kW class, with 15 years of lifetime, fast recurring delivery and high launcher flexibility. The on-board software (OBSW) is highly compositional as it must be adoptable for a wide range of missions. This paper sketches the design approach and the software architecture. The technical innovation of the software design is the application of object-oriented methods, the utilization of state-charts in modeling and the generation of large portions of the code from the model. The architectural innovation is the application of an event-driven concept.

Author M.,Universitatsallee 27 29 | Te Hennepe F.,Universitatsallee 27 29 | Ernst R.,Universitatsallee 27 29 | Bewick C.,Universitatsallee 27 29 | And 2 more authors.
Proceedings of the International Astronautical Congress, IAC | Year: 2015

This paper will present an overview of the OHB satellite design for the planned bistatic L-band radar mission Tandem-L. In particular, the challenges in the satellite design will be addressed and solutions presented. In 2012, the German space agency DLR and Japanese space agency JAXA agreed on their close cooperation in the definition of the Tandem-L mission. Tandem-L is anticipated to be a highly innovative L-band SAR mission for the global observation of dynamic processes on the Earth's surface. Its mission objectives include: • global measurement of 3-D forest structure and biomass for a better understanding of ecosystem dynamics and the carbon cycle • systematic recording of deformations of the Earth's surface with millimeter accuracy for earthquake research and risk analysis • quantification of glacier movements and melting processes in the polar regions for improved predictions of sea level rise • high resolution measurement of variations in soil moisture close to the surface for advanced water cycle research • systematic observation of coastal zones and sea ice for environmental monitoring and ship routing • monitoring of agricultural fields for crop and rice yield forecasts • emergency observations for disaster mitigation, recovery and prevention The Tandem-L space segment will consist of two radar satellites in low Earth orbit, which will be operated in two alternating mission phases that involve flying either in close formation or in constellation. Both satellites will implement an L-band (23.6 cm wavelength) synthetic aperture radar (SAR) instrument enabling bistatic radar measurements leading to Polarimetric, single-pass interferometric and tomographic data products. For the implementation of the SAR instrument, a large deployable reflector will be embarked, which will be complemented by high fidelity radar electronics enabling innovative techniques such as scan-on-receive (SCORE) and staggered SAR. In 2014, two parallel phase A studies were initiated to investigate the feasibility of the satellite design. This paper will present the results of this study, focusing on the design challenges on both platform and satellite level, which will mostly deal with meeting the stringent performance requirements under the influence of a large déployable reflector. Copyright © 2015 by the International Astronautical Federation, All rights reserved.

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