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Flechtner F.,German Research Center for Geosciences | Neumayer K.-H.,German Research Center for Geosciences | Dahle C.,German Research Center for Geosciences | Dobslaw H.,German Research Center for Geosciences | And 3 more authors.
Surveys in Geophysics | Year: 2015

The primary objective of the gravity recovery and climate experiment follow-on (GRACE-FO) satellite mission, due for launch in August 2017, is to continue the GRACE time series of global monthly gravity field models. For this, evolved versions of the GRACE microwave instrument, GPS receiver, and accelerometer will be used. A secondary objective is to demonstrate the effectiveness of a laser ranging interferometer (LRI) in improving the satellite-to-satellite tracking measurement performance. In order to investigate the expected enhancement for Earth science applications, we have performed a full-scale simulation over the nominal mission lifetime of 5 years using a realistic orbit scenario and error assumptions both for instrument and background model errors. Unfiltered differences between the synthetic input and the finally recovered time-variable monthly gravity models show notable improvements with the LRI, on a global scale, of the order of 23 %. The gain is realized for wavelengths smaller than 240 km in case of Gaussian filtering but decreases to just a few percent when anisotropic filtering is applied. This is also confirmed for some typical regional Earth science applications which show randomly distributed patterns of small improvements but also degradations when using DDK4-filtered LRI-based models. Analysis of applied error models indicates that accelerometer noise followed by ocean tide and non-tidal mass variation errors are the main contributors to the overall GRACE-FO gravity model error. Improvements in these fields are therefore necessary, besides optimized constellations, to make use of the increased LRI accuracy and to significantly improve gravity field models from next-generation gravity missions. © 2015 Springer Science+Business Media Dordrecht

Agency: European Commission | Branch: FP7 | Program: CP | Phase: ICT-2011.2.1 | Award Amount: 8.09M | Year: 2011

The ARCAS project proposes the development and experimental validation of the first cooperative free-flying robot system for assembly and structure construction. The project will pave the way for a large number of applications including the building of platforms for evacuation of people or landing aircrafts, the inspection and maintenance of facilities and the construction of structures in inaccessible sites and in the space.\nThe detailed scientific and technological objectives are:\n1)New methods for motion control of a free-flying robot with mounted manipulator in contact with a grasped object as well as for coordinated control of multiple cooperating flying robots with manipulators in contact with the same object (e.g. for precise placement or joint manipulation)\n2)New flying robot perception methods to model, identify and recognize the scenario and to be used for the guidance in the assembly operation, including fast generation of 3D models, aerial 3D SLAM, 3D tracking and cooperative perception\n3)New methods for the cooperative assembly planning and structure construction by means of multiple flying robots with application to inspection and maintenance activities\n4)Strategies for operator assistance, including visual and force feedback, in manipulation tasks involving multiple cooperating flying robots\nThe above methods and technologies will be integrated in the ARCAS cooperative flying robot system that will be validated in the following scenarios: a) Indoor testbed with quadrotors, b) Outdoor scenario with helicopters, c) free-flying simulation using multiple robot arms.\nThe project will be implemented by a high-quality consortium whose partners have already demonstrated the cooperative transportation by aerial robots as well as high performance cooperative ground manipulation. The team has the ability to produce for the first time challenging technological demonstrations with a high potential for generation of industrial products upon project completion.

Agency: European Commission | Branch: H2020 | Program: RIA | Phase: COMPET-01-2014 | Award Amount: 2.73M | Year: 2015

Unrestricted access to Space low shock non-explosive actuators has been identified as an urgent action by the European Commission, the European Space Agency and the European Defence Agency. Project REACT proposal is oriented to permit the unrestricted access of Europe to the technology of high reliable non-explosive actuators based on SMA (Shape Memory Alloy) technology. The REACT (REsettable Hold-Down and Release ACTuator) device is a new Hold Down and Release Actuator (HDRA) for space applications that have been developed as an improved alternative to currently available devices. Specifically, the proposed project is focused on develop low shock resettable Hold Down and Release actuators and qualify them integrated in real space final user space applications that require this release devices, such as big structures deployment, space science payload subsystems deployment, launchers subsystems deployment and small satellites subsystems deployment. The TRL (Technology Readiness Level) expected to be obtained once the project concluded shall be 8. REACT project is aimed to optimize and evolve standard REACT devices designs recently qualified up to TRL6 in order to match the requirements of specific applications demanded by the space market and generate a competitive range of products. The product optimized for space market applications will be able to replace and improve the performance of currently available US components in different areas of application (launchers, science, telecom and Earth Observation applications). REACT project contemplates to develop new SMA material manufacturing techniques and new SMA alloys that fit the specific requirements of the final users also involved in the project. In addition, research and improve the actuator tribology will be a technical objective to be addressed during the project development. Finally it is addressed a complete qualification campaign in order to upgrade to TRL8 the REACT models.

Ward R.L.,Australian National University | Fleddermann R.,Australian National University | Francis S.,Australian National University | Mow-Lowry C.,Australian National University | And 22 more authors.
Classical and Quantum Gravity | Year: 2014

The Gravity Recovery and Climate Experiment (GRACE) mission, launched in 2002, is nearing an end, and a continuation mission (GRACE Follow-on) is on a fast-tracked development. GRACE Follow-on will include a laser ranging interferometer technology demonstrator, which will perform the first laser interferometric ranging measurement between separate spacecraft. This necessitates the development of lightweight precision optics that can operate in this demanding environment. In particular, this beam routing system, called the triple mirror assembly, for the GRACE Follow-on mission presents a significant manufacturing challenge. Here we report on the design and construction of a prototype triple mirror assembly for the GRACE Follow-on mission. Our constructed prototype has a co-alignment error between the incoming and outgoing beams of 9 μrad, which meets the requirement that this error must be less than 10 μrad. © 2014 IOP Publishing Ltd.

Gerberding O.,Leibniz University of Hanover | Gerberding O.,U.S. National Institute of Standards and Technology | Gerberding O.,University of Maryland University College | Diekmann C.,Leibniz University of Hanover | And 18 more authors.
Review of Scientific Instruments | Year: 2015

Precision phase readout of optical beat note signals is one of the core techniques required for intersatellite laser interferometry. Future space based gravitational wave detectors like eLISA require such a readout over a wide range of MHz frequencies, due to orbit induced Doppler shifts, with a precision in the order of μ rad / Hz at frequencies between 0.1 mHz and 1 Hz. In this paper, we present phase readout systems, so-called phasemeters, that are able to achieve such precisions and we discuss various means that have been employed to reduce noise in the analogue circuit domain and during digitisation. We also discuss the influence of some non-linear noise sources in the analogue domain of such phasemeters. And finally, we present the performance that was achieved during testing of the elegant breadboard model of the LISA phasemeter, which was developed in the scope of a European Space Agency technology development activity. © 2015 AIP Publishing LLC.

Arnold D.,University of Bern | Lutz S.,University of Bern | Dach R.,University of Bern | Jaggi A.,University of Bern | Steinborn J.,SpaceTech GmbH
International Association of Geodesy Symposia | Year: 2016

Real-time and near real-time coordinate estimation become increasingly important in many applications like, e.g., environmental hazard monitoring. The typical approach is based on a Precise Point Positioning (PPP), which has the advantage that all stations can be processed independently and, therefore, the processing of monitoring networks with a large number of stations becomes efficient due to parallelization. However, a PPP requires external satellite clock corrections and the accuracy of the obtained coordinates strongly depends on the consistent usage of these clock corrections and on their quality. Since the processing time for real-time products is strictly limited, it is clear that, in general, the quality of such clock corrections is degraded w.r.t. post-processed products. The purpose of this article is to demonstrate that the classical double-difference network approach, where no accurate satellite clock corrections are needed, has a lot of potential also for near real-time applications, when a latency of a few minutes is acceptable. The presented results were obtained in the framework of the establishment of a National Multi-Hazard Early Warning System in the Sultanate of Oman. © Springer International Publishing Switzerland 2015.

Guilbert-Lepoutre A.,European Space Agency | Guilbert-Lepoutre A.,University of Franche Comte | Besse S.,European Space Agency | Mousis O.,Aix - Marseille University | And 6 more authors.
Space Science Reviews | Year: 2015

Studying comets is believed to bring invaluable clues on the formation and evolution of our planetary system. In comparison to planets, they have undergone much less alteration, and should have therefore retained a relatively pristine record of the conditions prevailing during the early phases of the solar system. However, comets might not be entirely pristine. As of today, we have not been able to determine which of the observed physical, chemical and orbital characteristics of comets, after they have evolved for more than 4 Gyr in a time-varying radiative and collisional environment, will provide the best clues to their origin. Comet physical characteristics as inherited from their formation stage may be very diverse, both in terms of composition and internal structure. The subsequent evolution of comet nuclei involves some possible processing from radiogenic heating, space weathering and large- and small-scale collisions, which might have modified their primordial structures and compositions with various degrees. When comets enter the inner solar system and become active, they start to lose mass at a very high rate. The effects of activity on comet nuclei involve a layering of the composition, a substantial non-even erosion and modification of their size and shape, and may eventually result in the death of comets. In this review, we present the dominating processes that might affect comet physical and chemical properties at different stages of their evolution. Although the evolutionary track may be specific to each comet, we can focus on long-lasting modifications which might be common to all nuclei after their formation stage, during their storage in reservoirs in the outer solar system, and once comets enter the inner solar system and become active objects. © 2015, Springer Science+Business Media Dordrecht.

Fitzau O.,Fraunhofer Institute for Laser Technology | Herper M.,Fraunhofer Institute for Laser Technology | Giesberts M.,Fraunhofer Institute for Laser Technology | Nicklaus K.,SpaceTech GmbH | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

In scope of the ESA funded "High stability Laser" activity, a single-mode and single-frequency fiber power amplifier with 500 mW output power at 1064 nm wavelength has been developed. It is part of an elegant breadboard (EBB) which consists additionally of an ultra-stable Fabry-Perot reference for frequency stabilization. The monolithic fiber amplifier is seeded by a non-planar ring oscillator (NPRO) with a linewidth below 10 kHz. The amplifier is stabilized in power via pump diode modulation and achieves a RIN performance of < 0.01/sqrt(Hz) in the range from 10-3 Hz to 10 Hz and a polarization extinction ratio of >30 dB. © 2015 SPIE.

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